Advanced Automotive Engine Performance 1284145255, 9781284145250

Table of contents :
Title Page
Copyright Page
Brief Contents
Contents
Chapter 1 Strategy-Based Diagnostics
Introduction
Vehicle Service History
Strategy-Based Diagnostic Process
Documenting the Repair
Ready for Review
Key Terms
Review Questions
ASE Technician A/Technician B Style Questions
Chapter 2 Advanced Computerized Engine Control Diagnostics
ECM/PCM Operation Review
Power Train Control System Diagram
Engine Control Service Information
Engine Control Module Inspection
Ready for Review
Key Terms
Review Questions
ASE Technician A/Technician B Style Questions
Chapter 3 Port Fuel Injection System Diagnosis
Port Fuel Injection Component Review
PFI Service Information
PFI Injector Diagnosis and Service
PFI Fuel Pump Service Procedures
Switch Input Testing Procedures
Temperature Sensor Testing Procedures
Position Sensor Testing Procedures
Pressure Sensor and Mass Airflow Sensors
Case Study: Lack of MAF Signal
Ready for Review
Key Terms
Review Questions
ASE Technician A/Technician B Style Questions
Chapter 4 Direct Injection System Diagnosis
Gasoline Direct Fuel Injection Component Review
High-Pressure Fuel Pump Diagnosis
GDI System Maintenance
Operation of Combination PFI and GDI Systems
Case Study: DS-4 PFI/GDI Diagnosis
Ready for Review
Key Terms
Review Questions
ASE Technician A/Technician B Style Questions
Chapter 5 Advanced Ignition System Diagnosis
Describe OBD II Ignition
Ignition System Spark Testing
Inspect Spark Plugs
Inspect Spark Plug Wires
Inspect CKP/CMP Sensors
Inspect Ignition Timing
DTC-Based Ignition System Diagnosis
No DTC-Based Ignition System Diagnosis
Ready for Review
Key Terms
Review Questions
ASE Technician A/Technician B Style Questions
Chapter 6 On-Board Diagnostics II Diagnosis
OBD II Application
OBD II DTC Structure
OBD II Scan Tool Modes
Role of OBD II in Diagnosis
Testing at the DLC
OBD II Drive Cycles
Ready for Review
Key Terms
Review Questions
ASE Technician A/Technician B Style Questions
Chapter 7 Continuous Monitor Diagnostics
Introduction
OBD II Continuous Monitors
Component Monitor
Misfire Monitor
Fuel System Monitor
Ready for Review
Key Terms
Review Questions
ASE Technician A/Technician B Style Questions
Chapter 8 Noncontinuous Monitors: Oxygen Sensor and Secondary Air Monitor Operation and Diagnosis
Introduction
OBD II Heated Oxygen Sensor Operation
OBD II Oxygen Sensor Heater Circuit Analysis
Testing Heated Oxygen Sensor
Heated Air-Fuel Ratio Sensor Operation
Air-Fuel Ratio Heater Circuit Testing
Secondary Air Systems
Ready for Review
Key Terms
Review Questions
ASE Technician A/Technician B Style Questions
Chapter 9 Noncontinuous Monitors: Exhaust Gas Recirculation and Catalyst Diagnosis
Introduction
EGR Operation
EGR System Monitor Operation
OBD II Catalyst Systems Operation
Catalyst System Monitor DTC Cause
Ready for Review
Key Terms
Review Questions
ASE Technician A/Technician B Style Questions
Chapter 10 Noncontinuous Monitors: Evaporative Emissions System Diagnosis
Introduction
Evaporative Emissions System Overview
EVAP Monitor Test Results Analysis
EVAP Purge Flow Monitor Analysis
EVAP System Faults and Related Diagnostic and Repair Procedures
Ready for Review
Key Terms
Review Questions
ASE Technician A/Technician B Style Questions
Chapter 11 Engine Emissions Testing and Failure Diagnosis
Introduction
Perfect and Incomplete Combustion
Emissions Inspection and Maintenance Testing Methods
Emissions System Diagnosis
Ready for Review
Key Terms
Review Questions
ASE Technician A/Technician B Style Questions
Chapter 12 Engine Noise, Vibration, and Harshness Diagnosis
Introduction
Diagnosing Engine Noises
Valve Train Noises
Motor Mount Faults
Abnormal Combustion—Preignition and Detonation
Oil Consumption Testing
Diagnosing Head Gasket Failure and Coolant Loss without Visible Leaks
Ready for Review
Key Terms
Review Questions
ASE Technician A/Technician B Style Questions
Appendix A 2017 ASE Education Foundation Automobile Accreditation Task List Correlation Guide
Appendix B Preparing for the ASE Advanced Engine Performance Specialist Test (L1)
Appendix C Generic OBD II Codes Present on All OBD II Vehicles
Appendix D Vehicle Emissions Control Information Label
Glossary
Index

Citation preview

Advanced Automotive Engine Performance We Support

| Education Foundation

Michael Klyde, MA Professor, Cypress College Cypress, California

World Headquarters Jones & Bartlett Learning 5 Wall Street Burlington, MA 01803 978-443-5000 [email protected] www.jblearning.com Jones & Bartlett Learning books and products are available through most bookstores and online booksellers. To contact Jones & Bartlett Learning directly, call 800-832-0034, fax 978-443-8000, or visit our website, www.jblearning.com. Substantial discounts on bulk quantities of Jones & Bartlett Learning publications are available to corporations, professional associations, and other qualified organizations. For details and specific discount information, contact the special sales department at Jones & Bartlett Learning via the above contact information or send an email to [email protected]. Copyright © 2021 by Jones & Bartlett Learning, LLC, an Ascend Learning Company All rights reserved. No part of the material protected by this copyright may be reproduced or utilized in any form, electronic or mechanical, including photocopying, recording, or by any information storage and retrieval system, without written permission from the copyright owner. The content, statements, views, and opinions herein are the sole expression of the respective authors and not that of Jones & Bartlett Learning, LLC. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not constitute or imply its endorsement or recommendation by Jones & Bartlett Learning, LLC and such reference shall not be used for advertising or product endorsement purposes. All trademarks displayed are the trademarks of the parties noted herein. Advanced Automotive Engine Performance is an independent publication and has not been authorized, sponsored, or otherwise approved by the owners of the trademarks or service marks referenced in this product. There may be images in this book that feature models; these models do not necessarily endorse, represent, or participate in the activities represented in the images. Any screenshots in this product are for educational and instructive purposes only. Any individuals and scenarios featured in the case studies throughout this product may be real or fictitious, but are used for instructional purposes only. Production Credits General Manager: Kimberly Brophy VP, Product Development: Christine Emerton Product Owner: Kevin Murphy Product Development Manager: Amanda Brandt Manager, Project Management: Jessica DeMartin Digital Products Manager: Jordan McKenzie Project Specialist: Brooke Haley Director of Marketing Operations: Brian Rooney VP, Manufacturing and Inventory Control: Therese Connell Composition: S4Carlisle Publishing Services Project Management: S4Carlisle Publishing Services Cover Design: Scott Moden Text Design: Scott Moden Senior Media Development Editor: Troy Liston Rights Specialist: Maria Leon Maimone Cover Image (Title Page): © CDX Learning Systems Printing and Binding: LSC Communications

Library of Congress Cataloging-in-Publication Data Names: Klyde, Michael, author. | Goodnight, Nicholas, author. Title: Advanced automotive engine performance / Michael Klyde, instructor, Cypress College, Los Angeles, California, Nick Goodnight. Description: First edition. | Burlington, MA : Jones & Bartlett Learning, [2021] | Includes index. Identifiers: LCCN 2019036642 | ISBN 9781284145250 (paperback) Subjects: LCSH: Automobiles--Motors--Maintenance and repair. | Automobiles--Performance. Classification: LCC TL210 .K54 2021 | DDC 629.25/040288--dc23 LC record available at https://lccn.loc.gov/2019036642 6048 Printed in the United States of America 24 23 22 21 20

10 9 8 7 6 5 4 3 2 1

© Jones & Bartlett Learning.

Brief Contents CHAPTER

1

Strategy-Based Diagnostics

CHAPTER

2

Advanced Computerized Engine Control Diagnostics

CHAPTER

3

Port Fuel Injection System Diagnosis

CHAPTER

4

Direct Injection System Diagnosis

CHAPTER

5

Advanced Ignition System Diagnosis

CHAPTER

6

On-Board Diagnostics II Diagnosis

CHAPTER

7

Continuous Monitor Diagnostics

CHAPTER

8

Noncontinuous Monitors: Oxygen Sensor and Secondary Air Monitor Operation and Diagnosis

CHAPTER

9

Noncontinuous Monitors: Exhaust Gas Recirculation and Catalyst Diagnosis

CHAPTER 10

Noncontinuous Monitors: Evaporative Emissions System Diagnosis

CHAPTER 11

Engine Emissions Testing and Failure Diagnosis

CHAPTER 12

Engine Noise, Vibration, and Harshness Diagnosis

APPENDIX

A

2017 ASE Education Foundation Automobile Accreditation Task List Correlation Guide

APPENDIX

B

Preparing for the ASE Advanced Engine Performance Specialist Test (L1)

APPENDIX

C

Generic OBD II Codes Present on All OBD II Vehicles

APPENDIX

D

Vehicle Emissions Control Information Label

GLOSSARY INDEX

© Jones & Bartlett Learning.

Contents CHAPTER

1

Strategy-Based Diagnostics Introduction Vehicle Service History Strategy-Based Diagnostic Process Documenting the Repair Ready for Review Key Terms Review Questions ASE Technician A/Technician B Style Questions CHAPTER

2

Advanced Computerized Engine Control Diagnostics ECM/PCM Operation Review Power Train Control System Diagram Engine Control Service Information Engine Control Module Inspection Ready for Review Key Terms Review Questions ASE Technician A/Technician B Style Questions CHAPTER

3

Port Fuel Injection System Diagnosis Port Fuel Injection Component Review PFI Service Information PFI Injector Diagnosis and Service PFI Fuel Pump Service Procedures Switch Input Testing Procedures Temperature Sensor Testing Procedures Position Sensor Testing Procedures Pressure Sensor and Mass Airflow Sensors Case Study: Lack of MAF Signal Ready for Review Key Terms Review Questions

ASE Technician A/Technician B Style Questions CHAPTER

4

Direct Injection System Diagnosis Gasoline Direct Fuel Injection Component Review High-Pressure Fuel Pump Diagnosis GDI System Maintenance Operation of Combination PFI and GDI Systems Case Study: DS-4 PFI/GDI Diagnosis Ready for Review Key Terms Review Questions ASE Technician A/Technician B Style Questions CHAPTER

5

Advanced Ignition System Diagnosis Describe OBD II Ignition Ignition System Spark Testing Inspect Spark Plugs Inspect Spark Plug Wires Inspect CKP/CMP Sensors Inspect Ignition Timing DTC-Based Ignition System Diagnosis No DTC-Based Ignition System Diagnosis Ready for Review Key Terms Review Questions ASE Technician A/Technician B Style Questions CHAPTER

6

On-Board Diagnostics II Diagnosis OBD II Application OBD II DTC Structure OBD II Scan Tool Modes Role of OBD II in Diagnosis Testing at the DLC OBD II Drive Cycles Ready for Review Key Terms Review Questions ASE Technician A/Technician B Style Questions CHAPTER

7

Continuous Monitor Diagnostics Introduction OBD II Continuous Monitors Component Monitor Misfire Monitor Fuel System Monitor

Ready for Review Key Terms Review Questions ASE Technician A/Technician B Style Questions CHAPTER

8

Noncontinuous Monitors: Oxygen Sensor and Secondary Air Monitor Operation and Diagnosis Introduction OBD II Heated Oxygen Sensor Operation OBD II Oxygen Sensor Heater Circuit Analysis Testing Heated Oxygen Sensor Heated Air-Fuel Ratio Sensor Operation Air-Fuel Ratio Heater Circuit Testing Secondary Air Systems Ready for Review Key Terms Review Questions ASE Technician A/Technician B Style Questions CHAPTER

9

Noncontinuous Monitors: Exhaust Gas Recirculation and Catalyst Diagnosis Introduction EGR Operation EGR System Monitor Operation OBD II Catalyst Systems Operation Catalyst System Monitor DTC Cause Ready for Review Key Terms Review Questions ASE Technician A/Technician B Style Questions CHAPTER

10

Noncontinuous Monitors: Evaporative Emissions System Diagnosis Introduction Evaporative Emissions System Overview EVAP Monitor Test Results Analysis EVAP Purge Flow Monitor Analysis EVAP System Faults and Related Diagnostic and Repair Procedures Ready for Review Key Terms Review Questions ASE Technician A/Technician B Style Questions CHAPTER

11

Engine Emissions Testing and Failure Diagnosis Introduction Perfect and Incomplete Combustion Emissions Inspection and Maintenance Testing Methods Emissions System Diagnosis

Ready for Review Key Terms Review Questions ASE Technician A/Technician B Style Questions CHAPTER

12

Engine Noise, Vibration, and Harshness Diagnosis Introduction Diagnosing Engine Noises Valve Train Noises Motor Mount Faults Abnormal Combustion—Preignition and Detonation Oil Consumption Testing Diagnosing Head Gasket Failure and Coolant Loss without Visible Leaks Ready for Review Key Terms Review Questions ASE Technician A/Technician B Style Questions APPENDIX

A

2017 ASE Education Foundation Automobile Accreditation Task List Correlation Guide APPENDIX

B

Preparing for the ASE Advanced Engine Performance Specialist Test (L1) APPENDIX

C

Generic OBD II Codes Present on All OBD II Vehicles APPENDIX

D

Vehicle Emissions Control Information Label GLOSSARY INDEX

© Jones & Bartlett Learning.

Note to Students This book was created to help you on your path to a career in the transportation industry. Employability basics covered early in the text will help you get and keep a job in the field. Essential technical skills are built in, cover to cover, and are the core building blocks of an advanced technician’s skill set. This book also explores strategy-based diagnostics—a method used to solve technical problems correctly on the first attempt—and covers every task the industry standard recommends for technicians. As you navigate this textbook, ask yourself, “What does a technician need to know and do at work?” This textbook is set up to answer that question. Each chapter starts by listing the learning objectives that guide the technician’s focus for that chapter. Each chapter ends with review activities to reinforce the material presented and topics learned. The content of each chapter is written to explain each objective. As you study, continue to ask the question above. Gauge your progress by imagining yourself as the technician. Do you have the knowledge, and can you perform the tasks listed at the beginning of each chapter? Combining your knowledge with hands-on experience is essential to becoming a Master Technician. During your training, remember that the best thing you can do as a technician is to learn how to learn. This skill will serve you well because vehicles keep advancing, and good technicians keep up with those advances and seek opportunities for additional education. Stay curious. Ask questions. Practice your skills, and always remember that one of the best resources you have for learning is right there in your classroom: your instructor.

Best wishes and enjoy! The CDX Automotive Team

© Jones & Bartlett Learning.

Acknowledgments Contributors and Reviewers Matthew Buca Master Technician, GM World Class Instructor/Coordinator Stark State College North Canton, Ohio Rick Escalambre Automotive Technology Skyline College San Bruno, California Jeffrey Evans GM ASEP Assistant Professor Ivy Tech Community College Indianapolis, Indiana Nicholas Goodnight, PhD, CMAT, CMTT Assistant Professor Ivy Tech Community College Fort Wayne, Indiana Carl Hader Technical Education Grafton High School Grafton, Wisconsin Brad Hartwig Instructor Robert Huffman Associate Professor/Department Chair Ivy Tech Community College Fort Wayne, Indiana John Kasabian

Instructor Golden West College Huntington Beach, California John Kennedy Instructor University of Northwestern Ohio Lima, Ohio Scott Mayotte Instructor Concord Regional Technology Center Concord, New Hampshire Dan Vincent Professor/Program Coordinator St. Clair College of Applied Arts and Technology Windsor, Ontario, Canada

© Jones & Bartlett Learning.

CHAPTER 1

Strategy-Based Diagnostics LEARNING OBJECTIVES After studying this chapter, you should be able to: 1-1

Describe the purpose and use of vehicle service history.

1-2

Practice active listening.

1-3

Explain the importance of the strategy-based diagnosis process.

1-4

Verify the customers’ concerns.

1-5

Research possible faults and gather information.

1-6

Isolate the cause of concern using focused testing.

1-7

Perform the repair.

1-8

Verify the repair.

1-9

Apply the 3 Cs to documenting a repair.

1-10

Complete a repair order.

YOU ARE THE AUTOMOTIVE TECHNICIAN A regular customer brings his 2014 Toyota Sienna into your shop, complaining of a “clicking” noise when he turns the steering wheel. You ask the customer further questions and learn that the clicking happens whenever he turns the wheel, especially when accelerating. He tells you he has just returned from vacation with his family and has probably put 300 miles (482 km) on the car during their trip. What additional questions should you ask the customer about his concern, the clicking noise he hears when turning? How would you verify this customer’s concern? What sources would you use to begin gathering information to address this customer’s concern? Based on what you know thus far about the customer’s concern, which systems might be related to this customer’s concern?

Introduction The overall vehicle service involves three major components. Those pieces are gathering information from the customer, the strategy-based diagnostic process, and documenting the repair. The flow of the overall service can be seen below. 1. Initial information gathering is often completed by a service advisor (consultant) and should contain details about the customer concern and pertinent history. 2. Verifying the customer concern begins the strategy-based diagnostic process. Technicians will complete this step to ensure that a problem exists and that their repair eliminated it. 3. Researching the possible cause will provide a list of possible faults. The technician will expand this list as testing continues. 4. Testing will focus on the list of possibilities. Technicians will start with broad, simple tests that look at an entire system or group of components. Testing will progressively become more narrowly focused as it pinpoints an exact cause. 5. Repairs will be made using suggested tools and recommended procedures. This is done to ensure a reliable repair and that manufacturer requirements are met. 6. Repairs must always be verified. This confirms that the technician has completed the diagnosis accurately and completely. The repair must be documented. The technician has been doing this all along. When the customer concern is recorded, the tests are recorded, and the final repair procedure recorded, the repair has been documented.

Vehicle Service History 1-1 Describe the purpose and use of vehicle service history.

Service history is a complete list of all the servicing and repairs that have been performed on a vehicle (FIGURE 1-1). The scheduled service history can be recorded in a service booklet or owner’s manual that is kept in the glove compartment. The service history can provide valuable information to technicians conducting repairs. It also can provide potential new owners of used vehicles an indication of how well the vehicle was maintained. A vehicle with a regular service history is a good indication that all of the vehicle’s systems have been well maintained, and the vehicle will often be worth more during resale. Most manufacturers store all service history performed in their dealerships (based on the VIN) on a corporate server that is accessible from any of their dealerships. They also use this vehicle service history when it comes to evaluating warranty claims. A vehicle that does not have a complete service history may not be eligible for warranty claims. Independent shops generally keep records of the repairs they perform. However, if a vehicle is repaired at multiple shops, repair history is much more difficult to track and, again, may result in a denial of warranty claims.

FIGURE 1-1 Print outs of completed repair order as saved in the online repair order system. © Jones & Bartlett Learning.

Vehicle service history can be very valuable to the technician. This history is typically retrieved from service records kept by the shop, dealer network, original equipment manufacturer (OEM), or aftermarket service center. This information often contains a list of services performed on a vehicle and the date and mileage at which they were completed. Not all service history contains the same information. Some histories may only contain repair information, while others include every customer concern and maintenance task performed. This information can be very helpful when diagnosing a concern. Service history may help technicians diagnose a vehicle and can also be used to prevent costly duplicated repairs. TECHNICIAN TIP Technicians and service advisors should check the vehicle service history against the manufacturer’s service maintenance schedule to determine if the vehicle is due for scheduled maintenance. The maintenance schedule is a guide that indicates what service is due when; it can be found in the manufacturer’s service information and often in the owner’s manual. Keeping the vehicle well maintained can avoid a failure that strands the customer on the roadside.

Service history can also be used to guide repairs. Records of vehicle service history may indicate that the customer has recently been in for service and now has returned with a new concern. This all-toocommon situation is usually found to be caused by error during the previous service. When working on a vehicle that has returned after a recent repair, the previous technician’s work (whoever that may be) should be inspected meticulously. TECHNICIAN TIP A vehicle’s service history is valuable for several reasons: It can provide helpful information to the technician when performing repairs. It allows potential new owners of the vehicle to know how well the vehicle and its systems were maintained. Manufacturers use the history to evaluate warranty claims.

The service history may also show that the customer is returning for the same issue due to a component failure. The history might indicate when the component was installed, help the customer get their vehicle repaired, and help the shop to get paid under the component warranty. A vehicle that returns more than once for the same repair could be an indicator that an undiagnosed problem is causing these failures. The service history allows technicians to determine if the vehicle has been well maintained. This can be extremely useful when a technician suspects that lack of maintenance may be the cause of the problem. The vehicle’s service history helps technicians determine what maintenance needs to be performed, and therefore helps customers save money over time by preventing future costly repairs. Routine maintenance is essential on today’s modern automobile and prevents premature failures due to contamination and component wear. Today’s vehicles also require regular software updates. There are many advanced computer systems on modern vehicles. From time to time, updates will be available to fix a bug or glitch in the computer programming. These updates are often designed to eliminate a customer concern, improve owner satisfaction, or increase vehicle life. This is very similar to an update for your PC or mobile device. Service history will indicate to the technician that the vehicle may need an update. The technician will inspect the vehicle’s computer system and perform any needed updates as necessary. Service history can also be used to keep customers safe. Occasionally, manufacturers may need to

recall a vehicle for service due to a safety concern that has been identified for a vehicle (FIGURE 1-2). This means that the manufacturer has found that the potential exists for a dangerous situation to occur, and the vehicle must be serviced to eliminate it. Depending on the nature of the problem, recalls can be mandatory and required by law, or manufacturers may voluntarily choose to conduct a recall to ensure the safe operation of the vehicle or minimize damage to their business or product image. The service history would be used to verify that the vehicle is subject to the recall and has or has not had the recall service completed. The technician would perform the service, update the service history, and return the vehicle to the customer.

FIGURE 1-2 Recall notice example. © Jones & Bartlett Learning.

Description To review the vehicle service history, follow the steps in SKILL DRILL 1-1. SKILL DRILL 1-1 Reviewing Service History 1. Locate the service history for the vehicle. This may be in shop records or in the service history booklet within the vehicle glove compartment. Some shops may keep the vehicle’s service history on a computer. 2. Familiarize yourself with the service history of the vehicle. a. On what date was the vehicle first serviced? b. On what date was the vehicle last serviced? c. What was the most major service performed? d. Was the vehicle ever serviced for the same problem more than once? 3. Compare the vehicle service history to the manufacturer’s scheduled maintenance requirements, and list any

discrepancies. a. Have all the services been performed? b. Have all the items been checked? c. Are there any outstanding items?

Active Listening Skills 1-2 Practice active listening.

Depending on the size of a shop, the first point of contact for the customer is the service advisor or consultant. This person answers the phone, books customer work into the shop, fills out repair orders, prices repairs, invoices, keeps track of work being performed, and builds customer relations with the goal of providing a high level of customer support. The service advisor also serves as a liaison between the customer and the technician who is working on the vehicle. A service advisor or consultant may advance to become a service manager. In smaller shops, a technician may perform these duties. When the customer brings his or her vehicle in for service, the service advisor or technician should ask for more information than just the customer’s concern. It is important to let the customer speak while you use active listening skills to gather as many pertinent details as possible. Active listening means paying close attention to not only the customer’s words, but also to their tone of voice and body language. Maintain eye contact with the customer throughout your conversation and nod to show you understand and are paying attention. Do not interrupt. Wait for the customer to finish speaking before responding, then ask open-ended questions to verify that you have heard the complaint clearly and understand the problem. An open-ended question is one that cannot be answered with a yes or no, but instead requires the customer to provide you with more information about the problem (FIGURE 1-3). If the shop is noisy, try to find a quieter location in which to speak with the customer. Excellent communication helps ensure that all relevant information is collected. It also makes a good first impression with customers; they are likely to feel that they were listened to and cared for.

FIGURE 1-3 The active listening process. © Jones & Bartlett Learning.

Description Politely use open-ended questions to ask about any symptoms the customer may have noticed, such as: Under what circumstances does the concern occur or not occur? What unusual noises do you hear (e.g., squeaks, rattles, clunks, and other noises)? What odd smells or fluid leaks have you noticed? What recent work, service, or accessories have been added to the vehicle? What other recent changes or experiences have you had with the vehicle? What other systems seem to be operating improperly? Although problems may seem unrelated initially, when multiple systems fail at the same time, the issues are frequently related. Open-ended questions can provide valuable information to the technician who is performing the diagnosis.

Strategy-Based Diagnostic Process 1-3 Explain the importance of the strategy-based diagnosis process.

Diagnostic problems can be very challenging to identify and correct in a timely and efficient manner. Technicians will find that having a plan in place ahead of time will vastly simplify the process of logically and systematically (strategically) solving problems. The plan should be simple to remember and consistent in its approach; yet it must work for the entire range of diagnostic problems that technicians will encounter. In this way, technicians will have one single plan to approach any diagnostic situation they may encounter, and will be confident in their ability to resolve it. This problem solving plan is called the Strategy-Based Diagnostic Process. The strategy-based diagnostic process is focused on fixing problems correctly the first time. It is a scientific process of elimination, which is much the same process as a medical doctor uses for their diagnosis. It begins with identifying the customer’s concern and ends with confirming that the problem has been resolved. The purpose of the problem-solving process is twofold: to provide a consistent road map for technicians as they address customer concerns that require diagnosis, and to ensure that customer concerns are resolved with certainty. This process simplifies the problem-solving portion of the repair, making the job easier for the technician; it prevents technicians from having to work on the same job more than once; and it all but eliminates customer comebacks. While repeat customers are good for business, a customer coming back with the same problem is not. The customer is likely to be upset and the technician is likely to be working for free. In order to avoid this scenario, it is imperative to address customer concerns correctly the first time. Proper diagnosis is important to consumers and to the federal government. Federal and state law protects consumers against the purchase of vehicles with significant persistent defects. Technicians are held to a standard of reasonable repair times and limited visits for the same concern. Although the law varies from state to state, this means technicians must not return a vehicle to a customer without addressing the customer’s original concern. Also, technicians cannot make the vehicle unavailable to the customer for a long period while the vehicle is being repaired. The purpose of the state and federal laws is to protect consumers buying new vehicles. TECHNICIAN TIP Technicians need to do their best to find the issue and resolve it; otherwise, the vehicle may be required to be bought back from the customer, costing the dealership and manufacturer significant money.

Failure to comply with the state and federal law can be very expensive for the dealership and manufacturer. Although most state laws hold the manufacturer directly responsible, dealerships are also hurt by a loss in sales revenue, a loss in repair revenue, and irreparable damage to their customer and sometimes manufacturer relationships. Many state laws hold the manufacturer responsible for full purchase price, incurred loan fees, installed accessories, and registration and similar government charges. This can be a heavy cost on top of the value of the vehicle itself.

Need for the Strategy-Based Diagnostic Process Finding the source of every customer concern can prove to be a challenge. Novice technicians frequently struggle with diagnostics situations. Even some veteran technicians have difficulty tackling diagnosis on

some new technologies. However, if the strategy for solving a problem is generally the same every time, this greatly simplifies the process. Hopefully, by applying a strategy-based diagnostic process, technicians will resolve challenging customer concerns 100% of the time in an efficient manner. TECHNICIAN TIP The diagnostic process makes the technician’s job easier by providing a step-by-step strategy to solving the problem. It also answers the question: “Now what do I do?” As even the toughest job becomes easier, technicians will find their rate of diagnostic success increasing.

Customer comebacks occur when the customer picks up the vehicle after service, only to bring it back shortly thereafter with the same concern. This situation is understandably upsetting to the customer. Typically, the end result is wasted labor time and a loss in shop productivity. The customer is left with one of the following impressions: The work was not performed; The shop is incompetent; Or, worse yet, the shop was trying to scam the customer. Customer comebacks are usually caused by one of two avoidable reasons: 1. The customer concern is misinterpreted or misunderstood. This results in the technician “fixing” a problem that does not exist or missing a problem altogether. 2. The technician failed to verify that the original concern was resolved. Technicians are often hurried; some will forget to ensure that the repair they had performed actually fixed the original customer concern. Use of the strategy-based diagnostic process enables the technician and shop to make more money and satisfy more customers. This is a win-win situation for all involved. Using the strategy-based diagnostic process requires starting at the beginning and following it through to the end every time (FIGURE 1-4). This systematic approach will ensure the best results for each diagnostic situation.

FIGURE 1-4 The strategy-based diagnostic process. © Jones & Bartlett Learning.

Description

Step 1: Verify the Customer’s Concern 1-4 Verify the customers’ concerns.

The first step in the diagnostic process is to verify the customer’s concern. This step is completed for two

main purposes: To verify that the vehicle is not operating as designed To guarantee that the customer’s concern is addressed Failure to complete this step may result in wasted time, wasted money, and, worst of all, an unhappy customer. The customer is probably not an experienced automotive technician. For this reason, the customer does not always accurately verbalize the problem that may be occurring. Therefore, it is very important that you have a complete understanding of the customer’s concern before beginning the diagnosis. This will enable you to know with certainty that you have actually resolved the original concern after repairing the vehicle and before returning it to the customer. During this step, you may perform several of the following tasks, depending on the customer concern. First, ask the customer to demonstrate the concern, if possible. This may necessitate a test drive (FIGURE 1-5). The customer should be encouraged to drive the vehicle while you ride along as a passenger and gather symptoms and details about the concern. Seeing the customer recreate the concern in real time will often provide some much needed context to the problem. Having the customer demonstrate the concern is ideal in most situations, though not always possible. In the event that the customer is not present, you must do your best to recreate the concern on your own based on the information obtained from the customer. With or without the customer present, be sure to document in writing any details about the scenario in which the concern arises.

FIGURE 1-5 Ask the customer to describe the concern. © Jones & Bartlett Learning.

Next, make sure that the customer concern doesn’t fall outside the range of normal operation of the component or system. The manufacturer’s service information provides system descriptions and

expected operations; technicians can use these details, provided in the owner’s manual or in the vehicle service manual, to become familiar with the system and then explain its operation to the customer. Especially on new cars with many amenities, customers may not be familiar with the controls and subsequent operation. This can cause a customer to bring a vehicle in for service unnecessarily, due to unfamiliarity with the system controls. Many shops use online service (shop) manuals where you can quickly access any information related to the customer’s concern (FIGURE 1-6). Checking to make sure that the concern is really a fault, and not a normal operation, will avoid unnecessary diagnosis time. This is also an opportunity to provide excellent customer service by demonstrating the features and their controls to the customer.

FIGURE 1-6 A technician researching service information. © Jones & Bartlett Learning.

Conducting a quick visual inspection to look for obvious faults can be very helpful (FIGURE 1-7). However, it does not replace the need for testing and is absolutely not intended as a shortcut to the diagnostic process. With that said, the visual inspection can provide valuable information that may speed up the testing processes. The visual inspection provides an opportunity for a quick safety check by the technician and may help to avoid some potentially dangerous situations during service.

FIGURE 1-7 Performing a visual inspection. © Jones & Bartlett Learning.

While visual inspections can be very valuable, technicians must be careful not to jump to conclusions based on what they see. For example, a customer comes in with an illuminated and flashing overdrive light on the control panel. The technician has seen this problem before and it was caused by a bad solenoid pack in the transmission. If the technician decides that this problem is also caused by a bad solenoid pack, this determination is one that was reached solely on conjecture; no actual test was performed. Although the flashing light might indicate a fault with the solenoid pack, steps in the diagnostic process should never be skipped. This guess can lead to a very costly mistake when it is discovered that the new solenoid pack does not, in fact, fix the problem. In reality, the wiring harness to the transmission is frayed and shorting out. Had the technician performed a test, the cause of the customer concern could have been confirmed or denied before a solenoid pack was put in unnecessarily. While the visual inspection is very valuable, tests must always be performed to compare suspected faults against the expectations and specifications defined in the service information. When recreating the customer concern, the technician should operate the system in question in all practically available modes. System operation should be checked to see if there are other symptoms that may have gone unnoticed by the customer. These other symptoms can be very valuable when determining which tests to perform; they could save the technician significant time during the diagnosis. When recreating the customer concern, it is important to check the entire system for symptoms and related faults. Recreating intermittent faults can be a challenge. Intermittent symptoms often stem from a component or system that is failing or one where the nature of the fault is not yet clear. In these situations, the aforementioned check of system operation can prove to be highly valuable, as it may

uncover previously unnoticed but consistent symptoms. Attempting to repair an intermittent fault without consistent symptoms, data, or diagnostic trouble codes (DTCs) is a gamble, because a technician cannot be certain that the actual problem is isolated. This means that there would be no way to confirm with certainty that a repair was effective. The fault could appear again as soon as the vehicle is returned to the customer. To avoid such a situation, look for symptoms, data, or DTCs that are repeatable or consistent. Intermittent diagnosis may require the use of an oscilloscope (a specialized tool for looking at electrical waveforms), or a “wiggle” test (as the name implies, a test instrument is monitored as the electrical or vacuum harness is manipulated by hand). Some scan tools offer a "Check Mode" function that tightens up DTC set parameters. Using "Check Mode" may set a DTC that under normal set parameters would not occur. A DTC set in this manner now offers you an area to focus your diagnosis related testing. This can verify the customer concern and remove some of the challenge from the diagnosis of an intermittent fault. Lastly, but notably, save DTCs and freeze frame data. Freeze frame data refers to snapshots that are automatically stored in a vehicle’s power train control module (PCM) when a fault occurs; this is only available on vehicles model year 1996 and newer. Intermittent faults may be found by reviewing data stored just before, during, and after the fault occurred, similar to an instant replay. When working with computer controlled systems, it is very important to save the recorded data. It may become necessary to erase this information from the computer, though that should generally be avoided. This information is absolutely critical when the technician is trying to answer the questions, “When did this happen?” and “What was going on at the time?” TECHNICIAN TIP All too often, the customer does not have symptoms to share and their only concern is that the malfunction indicator is illuminated. In this situation, the data stored in the computer is invaluable. Record it and do not clear it out unless directed to do so in the manufacturer’s service procedure. Even then, you should capture the information before clearing the memory.

What will step one look like? When information is gathered and recorded for step one, it should contain the customer concern, any symptoms, and any retrieved DTCs. View the following example from a vehicle that has no reverse. The technician verified the customer concern and recorded: 1. Vehicle will not move when shifted into reverse. 2. Vehicle operates normally in all forward gears in OD, D, L2, and L1. 3. Current code P0868. Notice that the technician in this example verified and recorded the customer concern. The technician also tried other functions in the system. Specifically, the technician drove the vehicle and tested the other gears in each of the gear ranges and then recorded the results. The DTC data was also retrieved from the control module and recorded. Although it was short and concise, the information will be very useful in the next step.

Step 2: Researching Possible Faults and Gathering Information 1-5 Research possible faults and gather information.

The second step in the diagnostic process is to research possible faults that may be related to the customer’s concern. The goal of this step is to create a list of possible faults. The list is created based on the information gathered in step one. The list will later be narrowed down by the tests performed in step three until the cause of the concern has been confirmed. Before testing can begin, a technician must know what possible faults need to be tested. Researching

possible faults should begin broadly. Especially when diagnosing electrical and electronic systems, this step should begin at the system level and work down to individual components. For example, if a vehicle engine cranks, but will not start, a technician would list these familiar possible faults: Air, Fuel, Ignition, Compression, and Security. These possible faults are not single components, but rather they are systems. This is where a diagnosis should begin. Starting a diagnosis by listing the dozens of components for each system will make the job unreasonably time intensive. However, once a test determines that there is a fault within a specific system, the list should be expanded to encompass that particular system’s subsystems and components. This systematic elimination starts broadly and narrows, allowing technicians to work more efficiently. In the second step of the diagnostic process, the technician creates a list to help focus their tests. The list may aid in a simple process of elimination by testing one possibility after the next. The list can also start broadly and narrow as testing continues. When starting a list, it may look similar to the following: 1. 2. 3. 4. 5.

Air Fuel Ignition Compression Security

This list is broad and starts at the system level. As you’ll soon see in the next step, the technician would eliminate possible faults with a test that is focused on analyzing the whole system. When a system is located with a fault, in the ignition system for example, the list would become more specific: 1. 2. 3. 4. 5. 6. 7.

Spark plug Coil on plug CKP CMP Sensor triggers Harness Control module

The technician would again focus his or her testing on the list, seeking to eliminate possible faults until one is confirmed, repaired, and verified. Several great sources of information are available for researching possible faults, although the best source of information is usually the manufacturer’s service information system. These systems are typically found online; however, some manufactures still publish paper service manuals. The manufacturer’s service information contains definitions for diagnostic trouble codes, system description and operation, electrical wiring diagrams, diagnostic steps, repair procedures, and much more. Fault diagnosis should almost always begin with the factory service information. Other resources for identifying faults can be used in conjunction with the factory service information. As previously discussed, the vehicle service history can provide valuable insight into the past maintenance or lack thereof. It can also provide information about recent or repeated repairs. Technical service bulletins (TSBs) are service notifications and procedures sent out by the manufacturers to dealer groups alerting technicians about common issues with a particular vehicle or group of vehicles (FIGURE 1-8). Some aftermarket sources also exist for the pattern failures addressed by TSBs (FIGURE 1-9). Additionally, both original equipment manufacturers (OEM) and aftermarket technician support services offer hotlines, or call-in support, that specifically provide technical support to professional technicians. Some of these hotlines offer subscriptions to searchable web-based components. These resources do not guarantee a repair; that is still the responsibility of the technician. However, all of the sources mentioned here can be a huge help as technicians research possible faults.

FIGURE 1-8 Technical service bulletin. © Jones & Bartlett Learning.

Description

FIGURE 1-9 Aftermarket source. © Jones & Bartlett Learning.

While these resources are essential, the list of possible faults is just that: a list of possible faults. A technician must always be aware that steps in the diagnostic process cannot be skipped.

Step 3: Focused Testing 1-6 Isolate the cause of the concern using focused testing.

Step three of the diagnostic process involves focused testing. In this step technicians use their testing skills to eliminate possible faults from the list they created in step two. Steps two and three work together; testing will start at a system level and work down to subsystems, then finally to individual components. The idea of focused testing should be to eliminate as many potential faults as possible with each test. Focused testing is intended to eliminate possible causes with certainty. Each time a test is performed, the following three pieces of information must be recorded: A test description

An expectation A result TECHNICIAN TIP A repair should never be performed unless the possible fault has been verified through testing. Do not let a possible fault become a possible mistake. In some cases, the list of possible faults can be found in the service information, but many times the technician will need to produce the list based on the concern, the information gathered, and the results of the research.

These can be recorded on the repair order, electronic service record, or on an extra sheet of paper. Test records must be kept handy because they will become part of the documented record for this repair. The three pieces of test information are recorded carefully for several reasons. Having an expectation before a test is performed makes each test objective and effective. The expectation is what the result is compared against, in order to determine if the vehicle passed or failed. TECHNICIAN TIP The test description must provide enough information that someone could repeat the test with the same result. This is very important!

Many manufacturers, both original equipment and aftermarket, require that documented test results be submitted with each warranty claim. If the technician fails to document his or her work, the manufacturer will not pay the claim. The result is that the shop is out of money for the parts and service, and the technician will not be paid for their work. Be sure to document the work properly (FIGURE 1-10).

FIGURE 1-10 The test record should include the test description, expectation or specification, and the result of measurement. © Jones & Bartlett Learning.

Description 1. The test description is not long, or even a complete sentence; it is simply a brief description. It allows the reader to know what test was performed and on what component or system. The test description should be accurate enough that the reader could repeat the test with the same result. 2. The expectation should describe the expected result as if the system is operating normally. The expectation could come directly from the system specifications listed in the manufacturer’s service information or from system description and operation. 3. The result is the third part that must be recorded for each test. This information should accurately reflect what happened when the test was performed. In summary, the testing is focused on isolating a fault or faults from the list of potential faults, and the results are compared to the expectation.

Testing should begin broadly and simply. Consider the following example: A light bulb circuit is suspected of having a fault. If the light bulb is easily accessible, the first test might be to check the voltage drop (i.e., voltage used to push current through the bulb). If the result of the voltage drop measurement is as expected (i.e., within specification), then the problem is in the bulb or socket. In this test, the technician is able to check the integrity of the entire electrical circuit with one test. If the result of the measurement is outside of the expectation (i.e., out of specification), the technician would know that the bulb is not the source of the problem. Further testing would isolate the problem to the ground or power side of the circuit. The technician in the example performed a simple test with an easy expectation. The test allowed the technician to quickly determine the state of operation for the entire system/circuit and move on. If a fault had been found, then the technician would have isolated the cause of the customer’s concern to that particular system/circuit and would need to perform further testing to isolate the cause to a particular component. To do that, the technician would use the service information to determine what components comprise the system and adjust the list from step two to take into account the new information. Then testing would continue. The next test might measure voltage supply at the bulb (i.e., available voltage). In this way, the technician would be testing the power supply, the conductors, and the switch (assuming a power-side switched circuit). The technician would have an expectation for the circuit voltage and compare his or her result to this expected voltage. As we saw earlier, the technician is testing more than one component with a single test, thereby operating in an efficient manner. This strategy—starting with broad, simple tests and moving to more complicated, pinpoint tests— makes efficient use of the technician’s time while still effectively testing the possible faults. 1. A technician is investigating a customer concern of “engine cranks, no start.” The technician’s investigation might begin with a simple list. a. Battery voltage b. Scan tool engine speed data 2. The technician would then eliminate one or the other and expand the list. The technician would verify battery voltage is higher than 12.4 volts. The technician can then use the scan tool and note engine speed data during engine cranking. If the data remains at 0 RPM when cranking, the CKP sensor and related components will be the focus. If the data is normal (about 250 RPM) then the list will expand. a. Spark test b. Fuel pressure test c. Immobilizer system d. Mechanical failure (timing belt or chain for example) 3. Notice that the technician has moved from broad system tests to individual components or component groups. The technician’s test continues to become more specific as the possibilities are narrowed down. Technicians commonly encounter vehicles with more than one customer concern. When these concerns both originate from the same or companion systems, technicians are inclined to search for one cause to both problems. Unfortunately, trying to diagnose two faults at once can quickly become problematic and confusing. Instead, select the easier customer concern and follow it through to the end. If both problems were caused by the same faults, then both were fixed. If they were caused by two separate faults, the technician is no worse off for having fixed one concern. When selecting tests to perform, remember that they should be simple and easy (FIGURE 1-11). Except when following service procedures, you should select tests that have simple expectations, are easy to perform, and provide you with the maximum amount of information. This means simple tests that inspect an entire system or circuit are ideal ways to begin testing. Simple tests have expectations and results that are quickly understood and interpreted. They are short and involve basic tools and access to areas that are comfortable to reach.

FIGURE 1-11 Select tests that have simple expectations and are easy to perform.

When selecting tests, prioritize your testing. First choose tests that can be performed quickly and simply, even if they do not test an entire circuit. If a preferred test is in a difficult place to access, move to another test and come back to it, if needed. The answer may be found in the meantime and the timeconsuming test can be avoided. Simple and easy tests are ideal, but they must be measurable or objective. Yes, a visual inspection is a simple and valuable test, but a technician must determine what the issue is in an objective manner, with help from the service information. A guess based only on appearance is insufficient. If the service information says, “cracks in the serpentine belt indicate that it needs replaced,” the belt can be visually and objectively (yes or no) tested. The belt will either have the indicated wear or it will not. If the service information states, “Chain deflection cannot exceed 0.75,” then the deflection can be measured and compared to the specification. As testing continues, it may become necessary to use advanced tests, sophisticated equipment, additional time, or tests in areas difficult to access. Keeping initial testing simple and easy will produce the quickest, most reliable, and effective results. TECHNICIAN TIP When selecting tests, it is not a bad idea to choose those tests that might look at components of both systems (e.g., voltage drop on a shared electrical ground), but DO NOT attempt to test for both faults at once. While multiple faults within a companion or the same system often turn out to be related, they should be isolated and tested separately.

When testing, use the recommended procedures and equipment. Manufacturers frequently

recommend a particular procedure when testing one of their systems. Failure to follow the specified service procedure can result in the warranty claim being denied by the manufacturer. In that case, both the shop and the technician lose money. Manufacturers may recommend a certain procedure because of the way their system is designed or monitored. Technicians must also be very careful to perform tests safely (FIGURE 1-12).

FIGURE 1-12 Always perform all tests safely. © Jones & Bartlett Learning.

Description TECHNICIAN TIP When performing tests for an inspection under warranty, it is absolutely necessary to follow the manufacturers’ guidelines.

Beyond the mechanical dangers posed by automobiles, many of today’s vehicles have dangerously high fluid pressures and deadly high voltage. It is of the utmost importance for the safety of the technician, and those working in the area, that safety procedures are always followed. Proper test equipment and procedures are intended to test a particular component or system without causing any damage. Improper equipment or test procedures can create a second fault in the system being tested; making the technician’s job even more difficult. For example, front probing an electrical terminal with the lead of a DMM can cause the terminal to spread or deform. This can create an intermittent high resistance or open within the circuit that was not there prior to the technician’s test. Using the recommended equipment and procedures will help to ensure warranty claims are approved,

people are safe, and testing goes smoothly. When performing repairs, look beyond the obvious for the root cause. This simple suggestion can avoid customer comebacks. Novice technicians frequently have problems with misdiagnosing fuserelated issues. For example, a technician diagnoses a blown fuse as the cause of the customer concern. While replacing the fuse may have fixed the immediate fault, the technician did not look beyond the obvious. What causes a fuse to blow? Low resistance and increased amperage cause a fuse to blow. However, the technician did not test for one of these faults and the vehicle is likely to return with the same customer concern and the same blown fuse. In another example of incomplete reasoning, a technician diagnoses a leaky transmission cooler line. The line is chaffed and leaking. This cooler line runs along the frame rail; the inner and outer tie rods are immediately below. The technician diagnoses the vehicle while it is on a lift and the suspension is unloaded (increasing the distance between the hose and steering linkage). The technician should have looked for the root cause of the chaffing, but instead the vehicle and customer come back some time later for the same concern. The technician notices several broken clips that held the flexible line into place on the frame rail. In both cases, the technician will work for free to repair the same vehicle, because time was not taken to ask the question: “Did something else cause this failure?” Testing must be focused beyond the obvious to identify the root cause of the problem and consequently avoid customer comebacks. In summary, focused testing has several key elements. It picks up the possible faults identified in step two and begins testing each one broadly, narrowing down to more specific tests. Focused testing requires accurately documenting the tests performed, including a test description, expectation, and result, each and every time a test is performed. It should also be performed in a safe and proper manner, following manufacturers’ guidelines and safety protocols. Focused testing is a safe, accurate, and repeatable method for isolating possible faults.

Step 4: Performing the Repair 1-7 Perform the repair.

The fourth step of the diagnostic process is to perform the repair. Although performing the repair is often the most straightforward step in the process, technicians must still avoid making several common mistakes. The following tips will help you to perform an effective and reliable repair.

Use Proper Service Procedures Manufacturers will often indicate what procedures are appropriate for their vehicles and components. Many design features and component materials require certain procedures be used and others avoided. Following the manufacturer’s service information can prevent premature failure of the repair (FIGURE 113). For example, repair methods that are safe around the home may be unacceptable in the automotive industry. The use of twist-on wire connectors can create an unreliable and potentially dangerous electrical situation when used in a vehicle. Additionally, warranties, both original equipment and aftermarket, rely on the technicians’ adherence to the manufacturer’s service information. If technicians fail to do so, the warranty claim can go unpaid and the shop will lose money. Therefore, it is important for reliable repairs and warranty reimbursements that technicians follow the service information when performing repairs.

FIGURE 1-13 A typical shop manual page has a task description broken into steps and diagrams or pictures to aid the technician. © Snap-on Incorporated.

Use the Correct Tool for the Job Failure to use the correct tool can lead to a customer comeback and injury to the technician. Proper tool selection is essential. If you are ever in doubt, refer to the manufacturer’s service information. Improper tool use or selection can damage the component being installed or other components around it. For example, a technician may choose to install a pump busing with a hammer instead of using the recommended press and bushing driver. This incorrect tool selection can easily lead to misalignment, or damage to the bushing, pump, or torque converter. Using the wrong tool (or the right tool in the wrong manner) can also damage the tool and potentially injure those in the area. For example, if a technician is using a hardened chrome socket on an impact wrench, the socket may shatter, sending shrapnel flying. Using the correct tool for the job will produce better work and ensure the safety of the technician.

Take Time to Perform the Repair Properly Because technicians are frequently paid by the job, or a flat rate, rather than paid hourly, it is possible for technicians to feel a rush to complete their current job. Rushing increases the likelihood of a mistake. If a mistake occurs, the customer will come back with the vehicle and the technician will work for free to repair the mistake. For example, if a technician replaces a water pump and fills the coolant without bleeding the system, a potentially damaging situation can occur. The trapped gas can affect the flow of coolant and create a hot spot in the cylinder head. This can lead to warning lights, poor performance, and possible engine damage. Take a little extra time to ensure that the work is performed correctly, with the right tools and the proper service procedures. Taking time to perform the repair will ensure fewer “comebacks” and more satisfied customers.

Make Sure the Customer Approves of the Repair

This may seem trivial, but it is extremely important. Most states’ laws protect consumers by preventing unauthorized services from being charged or performed. This means that technicians cannot just repair a vehicle and charge the customer for the cost incurred. If the customer is paying, shops must receive a customer’s approval prior to performing repairs. TECHNICIAN TIP It is very important to quote accurately and wait for approval before performing repairs on a customer’s vehicle.

Check for Updates Prior to the Repair It is also good practice to check for updated parts and software/firmware before performing a repair. It is possible that manufacturers have become aware of a problem with a particular component or software version and issued a software update or produced an updated component. When performing repairs it is a good idea to check for these sorts of updates (often found in TSBs), because it may prevent a customer comeback. Software updates are often downloaded from the manufacturer’s website. For hard parts, the best resource is frequently the respective dealership’s parts department. Technical service bulletins also provide information related to unexpected problems, updated parts, or changes to a repair procedure on a particular vehicle system, part, or component. The typical TSB contains step-by-step procedures and diagrams on how to identify if there is a fault and perform an effective repair. Shops typically keep TSBs in a central location, or you may look them up online. Compare the information contained in the TSB with that of the shop manual. Note the differences and, if necessary, copy the TSB to take with you to perform the repair.

Pay Attention to Details Performing the repair is straightforward but requires attention to detail. There are several things to keep in mind. Proper service procedures can be located in the manufacturer’s service information. The correct tool for the job will lessen injury and ensure reliability. Use the necessary time to make sure that the repair was completed correctly. Document your work. These tips can greatly improve the likelihood of a successful repair, but the process does not stop with the repair.

Step 5: Verify the Repair 1-8 Verify the repair.

The most important step of the strategy-based diagnostic process is verifying the repair. The reason that this is the most important step is straightforward. The vehicle would never have been in the shop if the customer did not have a concern. If the technician fails to address the original concern, the customer may view the trip as ineffective, a waste of their time and money. Even when a valid repair that makes the vehicle safer and more reliable was performed, the customer will still be unsatisfied if his or her original concern was not addressed. For example, a customer brings the vehicle into the shop for a sticky glove box latch. The technician identifies and repairs a dangerous brake line leak, but fails to fix the glove box. Some customers may view this trip to the shop as unsuccessful because it failed to fix their original issue. When verifying the repair, technicians must always double check their work. This is a valuable confirmation that the repair performed did fix the identified problem. There are several ways to verify a repair, but generally, the simplest method is the best method. For example, a customer is concerned that the wipers stop moving when the switch is moved into the high position. In step one, the technician will verify that the customer concern and fault exist by turning the wiper switch to all positions. Then the technician uses the wiring diagram (step 2) to diagnose a fault

(step 3) within the wiring harness and repairs it (step 4). The technician could then verify the repair by performing the last diagnostic test (from step 3) again. In most cases, the repair would be confirmed if the results had changed and were within expectation/specification. But what if there was a second problem affecting the wipers such as worn brushes in the motor, or the wiper linkage fell off of the pivot on one side? The customer would still have issues with the wipers and would likely to be unhappy with the repair. So while performing the last diagnostic test (step 3) is a valid verification method, it is not foolproof. An easier method exists: simply return to the process used in step one to verify the customer concern. If the repair has eliminated the problem, the technician should now be able to turn the wiper switch to all positions (step 1) and confirm normal operation. Be certain to perform the same inspections used to verify the customer concern in step one after the repair is performed. This may include checking the entire system operation, not just a single function. This method of verifying that the customer concern is resolved is usually best in most scenarios because it is simple and it is exactly what the customer will do to check your work. However, sometimes verifying the repair requires a more complicated means of verification. A common concern that falls into this scenario is as follows: The customer brings their vehicle in with a concern that the MIL (malfunction indicator lamp) or “check engine” light is illuminated. In this scenario, NEVER verify the repair by simply checking to see that the light is off. While this is what the customer will do to check your work, the failure of the MIL to light can often be misleading and result in a comeback for the exact same problem. This can occur because the MIL is illuminated when tests run by the computers in the vehicle fail. The computers are constantly running tests, but some tests require very specific conditions before they can be run and, hence, fail. Due to the requirements for the conditions to be right, simply checking to see if the light is illuminated is an inadequate method of verification. For more complicated computer-controlled systems, the best method of verification is checking the test results stored on the vehicle’s computer. This option will require an electronic scan tool that communicates with the vehicle’s computer, along with a high level of diagnostic experience and service information to verify that the concern has been fully resolved. If the communication option is not available, the second best method of verification is repeating the last diagnostic test performed (in step 3) and confirming that the result has changed to now match the expectation/specification. Complicated computer-controlled systems require that the technician do more than verify the customer concern is eliminated. The technician will have to repeat a diagnostic test (step 3) or view test results stored on the vehicle’s computer (this is the preferred method) in order to verify that the repair was effective. Step five of the strategy-based diagnostic process is the most important. A vehicle should never be returned to a customer without this step completed. TECHNICIAN TIP The job is not complete until you have verified that the repair resolved the customer’s concern.

Documenting the Repair The first two components, gathering information from the customer and the strategy-based diagnostic process, have already been described; this section discusses documentation. The repair is documented for several reasons: accurate vehicle history, returns or comebacks, and OEM or aftermarket warranties. Keeping accurate service records will help technicians to know what services and repairs have been performed on a vehicle when it needs any future services. This can be invaluable during the diagnostic process and can also help service advisors and technicians identify what maintenance or recall work still needs to be completed. Documenting the repair also helps technicians in the event that a vehicle returns, now or in the future, with the same customer concern or fault. This can help to identify defective parts or common problems. Warranty work is another reason that all repairs must be documented. Whether the repair is submitted to an original equipment manufacturer or to an aftermarket warranty company for reimbursement, the repair must be well documented. Warranty clerks will review the repair order to ensure that proper testing and repair procedures have been followed. Technicians must document their work to ensure that the shop, and in turn the technician, get paid for the work performed. Finally, documenting the work provides the shop with a record that the work was initiated and completed. This is important in case the vehicle is later involved in an accident or other mishap and the shop is involved in a lawsuit. It is important to have the customer sign or initial, depending on shop policy, the repair order, to verify that the customer accepted the repair.

The 3 Cs of Documentation 1-9 Apply the 3 Cs to documenting a repair.

When documenting a repair, technicians need to remember the 3 Cs: concern, cause, and correction (FIGURE 1-14).

FIGURE 1-14 The 3 Cs of documenting the repair. © Jones & Bartlett Learning.

Description

Concern The main focus of the 3 Cs is the customer concern, which is also the focus of step one of the diagnostic process. Often the concern is documented on the repair order prior to the technician receiving the vehicle. If this is the case, the technician who works on the vehicle should take time to fully understand the concern, read the repair order, and possibly talk further with the customer to understand the nature of the problem. Think through the problem and develop a strategy to attack it. Other symptoms and diagnostic troubles codes are some examples of other information that should be included in the “concern.”

Cause The second C in the 3 Cs is cause, which details the cause of the customer concern. This correlates to the documentation done in step three of the diagnostic process. The technician should document any tests that they perform with enough detail that they can be repeated, as well as specifications/expectations, and results. This goes for all tests, even the simple ones.

Correction The technician should then document the last C, the correction. This must include the procedure used as well as a brief description of the correction. This information comes from the fourth step of the diagnostic process. When documenting the repair order, technicians should include the customer concern and symptoms (DTCs are symptoms); brief descriptions of tests; expectations; and results, along with the procedure and repair that were performed. The technician should also include all parts that were replaced as well, and noted if they were new or used, OEM, or aftermarket.

Other Parts of Documentation Additional service recommendations should also be documented on the repair order. While working on the vehicle, technicians should also be mindful of other work that may need to be performed. Technicians are obligated to make the customer aware of safety concerns that require attention. Customers may be unaware of a potential hazard or lack of maintenance. Bringing this to the attention of the customer right away can help the technician, as well as the customer. For example, if the technician is already working on the vehicle, they would not have to remove the vehicle from the service bay, bring in a new vehicle, and start all over. Repairing multiple issues in one trip to the service bay makes good use of the technician’s time. It also improves customer relations by bringing the customer’s attention to problems and thereby preventing possible failures. TECHNICIAN TIP A repair order is a legal document that can be used as evidence in the event of a lawsuit. Always make sure the information you enter on a repair order is complete and accurate. The information required on a repair order includes: date; customer’s name, address, and phone number; vehicle’s year, make, model, color, odometer reading, and VIN; and description of the customer’s concern. Store repair orders in a safe place, such as in a fireproof filing cabinet or electronically on a secure computer network. Finally, to prevent future complications, it is a good idea to have the customer sign or initial the repair order, indicating that they understand and agree to the needed repair. Having the customer’s signature will help prevent the shop from being held liable in an accident involving the vehicle later.

For example, a technician may be changing the fluid in a transmission and notice that the brake friction pads are extremely low. Bringing this to the attention of the customer can result in additional work for the technician and save the customer from a potentially more costly repair. For this reason, technicians should also note safety issues and maintenance items on the repair order.

Repair Order 1-10 Complete a repair order.

A repair order is a key document used to communicate with both your customers and coworkers.

Thoroughly document the information provided by the customer on the repair order; every bit of it may be helpful during the diagnosis (FIGURE 1-15). If you are not typing this information, make sure your handwriting is clear and easy for others to read. Unfortunately, if documentation of a complaint is not done well, the technician could be led on a much longer diagnostic path, wasting everyone’s time. It can also be a time-consuming process for the diagnosing technician to make contact with the customer in order to get more information that was missed the first time. From time to time, it may be inevitable that the customer will need to be contacted for further inquiry after the initial visit. However, carefully gathering information from the customer on their initial visit will save time, prevent inconveniencing the customer, and aid in the diagnostic process.

FIGURE 1-15 A repair order. © Jones & Bartlett Learning.

Description To complete a repair order using the 3 Cs, follow the steps in SKILL DRILL 1-2. SKILL DRILL 1-2 Completing a Repair Order 1. Greet the customer. 2. Locate a repair order used in your shop and obtain or verify the customer’s name, address, and phone number. 3. Obtain details about the vehicle, including the year, make, model, color, odometer reading, and VIN. 4. Ask the customer to tell you more about the concern by using open-ended questions, such as “When does problem occur?” “At what speed(s)?” “How do you experience the problem?” “How long has this been occurring?” “How many passengers do you typically carry?” Type or clearly write the customer’s responses on the repair order. 5. Ask the customer about other changes with the vehicle, such as recent work, or recent travel. Type or clearly write the customer’s responses on the repair order. 6. Remembering the lessons learned regarding the proper diagnostic process, begin to verify the customer’s concern by first performing a visual inspection. 7. If you see nothing unusual during your visual inspection, continue to verify the customer’s concern by conducting a road test of the vehicle. The customer may ride along, if possible, to help identify the issue as it occurs, or you may conduct the test by yourself. Following the test drive, after verifying the customer’s concern, record it on the repair order. 8. The second step of the diagnostic process is to research the possible faults, and gather information. Access the vehicle service history to determine if the vehicle has experienced a similar problem in the past, requires a routine service maintenance, or has been serviced recently. Document this information, if applicable, on the repair order. 9. Conduct research by accessing various sources of information related to the vehicle, such as the vehicle service manual or the owner’s manual. Check to see if a TSB related to the issue exists. As part of the process, rule out the possibility that the customer’s concern is a normal operation of the vehicle. 10. Now that you have your broad list of possible faults related to the concern, begin step three, focused testing. Choose one of the possible broad faults you identified in step two. Now refer to the service manual to locate information that matches the concern. Service manuals usually contain diagnostic charts to aid in the focused testing process. 11. Conduct a test and record its description, your expectation, and the result on the repair order or another piece of paper. Continue to check each possible fault until you identify the cause of the concern. 12. Once you have identified the fault, you’re ready for step four, performing the repair. You would inform the customer of your finding and obtain his or her approval to make the repair. Pending customer approval, you would then follow proper safety procedures and use the manufacturer’s guidelines to correct the problem, being sure to use the correct tools and taking the time to complete the job properly. 13. Once you’ve made the repair, you are ready for step five, verifying the repair. The simplest way to verify that you have addressed and corrected the customer’s concern is to repeat the test drive. Take the vehicle for a test drive and repeat the tests you initially performed. Is the issue gone? If so, you have verified the repair and can return the vehicle to the customer.

14.

Document the correction on the repair order. If the issue is not resolved, you must return to your list of possible faults and continue testing after first alerting the customer that additional work and time will be necessary.

WRAP-UP Ready for Review Service history is typically retrieved from service records kept by the shop, dealer network, original equipment manufacturer (OEM), or aftermarket service center and contains a list of services performed on a vehicle and the date and mileage at which they were completed. The service history allows technicians to determine if the vehicle has been well maintained. This can be extremely useful when a technician suspects that lack of maintenance may be the cause of the problem. Failure to comply with the state and federal law can be very expensive for the dealership and manufacturer. Today’s vehicles also require regular software updates made available to fix a bug or glitch in the computer programming. These updates are often designed to eliminate a customer concern, improve owner satisfaction, or increase vehicle life. The strategy-based diagnostic process is focused on fixing problems correctly the first time. It begins with identifying the customer’s concern and ends with confirming that the problem has been resolved. The problem-solving process provides a consistent road map for technicians as they address customer concerns that require diagnosis and to make sure that customer concerns are resolved with certainty. Strategy-based diagnosis simplifies the problem-solving portion of the repair, making the job easier for the technician; it prevents technicians from having to work on the same job more than once; and it all but eliminates customer comebacks. Customer comebacks are usually caused by the customer concern being misinterpreted or misunderstood or failing to verify that the original concern was resolved. The strategy-based diagnostic process begins by gathering preliminary information from the customer and by reviewing the vehicle’s service history. The first step in the diagnostic process is to verify the customer concern. This step is completed for two main purposes: verify that there is an actual problem present, and guarantee that the customer’s concern is addressed. Visual inspections can be very valuable, but technicians need to be careful not to jump to conclusions. DTCs (diagnostic trouble codes) and freeze frame data should always be saved and recorded on the repair order. Freeze-frame data provide a snapshot of the entire engine data when the DTC occurs, which allows for duplication of the condition so that the DTC can be replicated. The second step in the diagnostic process is to research possible faults. The goal of this step is to create a list of possible faults. The list will be created based on the information gathered in step 1 and narrowed down by the tests performed in step 3 until the cause of the concern has been confirmed. The best source of information is usually the manufacturer’s service information system. Technical service bulletins (TSBs) are service notifications and procedures sent out by the manufacturers to dealer groups, alerting technicians to common issues with a particular vehicle or group of vehicles. Some aftermarket sources also exist for the pattern failures addressed by TSBs. A technician must always be aware that steps in the diagnostic process cannot be skipped. A repair should never be performed unless the possible fault has been verified through testing. Step 3 of the diagnostic process involves focused testing, where technicians use their testing skills to eliminate possible faults from the list they created in step two. Steps 2 and 3 work together, because testing starts at a system level and works down to subsystems, then finally to individual components.

When selecting tests prioritize your testing. First choose tests that can be performed quickly and simply, even if they do not test an entire circuit. If a preferred test is in a very difficult place to access, move to another test and come back to it, if needed. Following manufacturers’ guidelines and safety protocols keeps technicians safe. Focused testing is a safe, accurate, and repeatable method for isolating possible faults. Once the fault has been isolated, it is time to perform the repair. The fourth step of the diagnostic process is to perform the repair. Performing the repair is often the most straightforward step in the process. Use proper service procedures when performing a repair. Manufacturers often indicate what procedures are appropriate for their vehicles and components. Use the correct tool for the job when performing a repair. Failure to use the correct tool for the job can lead to a customer comeback and injury to the technician. Take time to perform the repair properly. Technicians are frequently paid by the job, or flat rate, rather than paid hourly, it is possible for technicians to feel a rush to complete their current job. Rushing increases the likelihood of a mistake and the next time you may pay for it. The most important step of the strategy-based diagnostic process is verifying the repair. The reason that this is the most important step is straightforward. The vehicle would never have been in the shop if the customer did not have a concern. Verifying the original concern is the best method of double-checking your work and meeting your customers’ expectations. The job is not complete until you have verified that the repair resolved the customer’s concern. Documentation is key to effective and efficient repairs. Keeping all the information available to the service advisor, technician, and the customer allows for a more open dialogue which can limit the confusion of the repair process. The repair is documented for several reasons: accurate vehicle history, returns or comebacks, and warranties. Keeping accurate service records will help technicians to know what services and repairs have been performed on a vehicle when it needs any future services. When documenting a repair, technicians need to remember the 3 Cs: concern, cause, and correction. When documenting the repair order, technicians should include the customer concern and symptoms (diagnostic trouble codes are symptoms) and a brief description of tests, expectations, and results, along with the procedure and repair that were processed.

Key Terms 3 Cs A term used to describe the repair documentation process of 1st documenting the customer concern, 2nd documenting the cause of the problem, and 3rd documenting the correction. Aftermarket A company other than the original manufacturer that produces equipment or provides services. Cause Part of the 3 Cs, documenting the cause of the problem. This documentation will go on the repair order, invoice, and service history. Concern Part of the 3 Cs, documenting the original concern that the customer came into the shop with. This documentation will go on the repair order, invoice, and service history. Correction Part of the 3 Cs, documenting the repair that solved the vehicle fault. This documentation will go on the repair order, invoice, and service history. Freeze frame data Refers to snapshots that are automatically stored in a vehicle’s power train control module (PCM) when a fault occurs (only available on model year 1996 and newer). Intermittent faults A fault or customer concern that you can not detect all of the time and only occurs sometimes. Original equipment manufacturer (OEM) The company that manufactured the vehicle. Repair order The document that is given to the repair technician that details the customer concern and any needed information. Service advisor The person at a repair facility that is in charge of communicating with the customer. Service history A complete listing of all the servicing and repairs that have been performed on that vehicle. Strategy-Based Diagnostic Process A systematic process used to diagnose faults in a vehicle. Technical service bulletin (TSB) Information issued by a manufacturer to alert technicians of expected problems or changes to repair procedures.

Review Questions 1. When a vehicle comes in for repair, detailed information regarding the vehicle should be recorded in the: a. service booklet. b. repair order. c. vehicle information label. d. shop manual. 2. The service history of the vehicle gives information on whether: a. the vehicle was serviced for the same problem more than once. b. an odometer rollback has occurred. c. the vehicle meets federal standards. d. the vehicle has Vehicle Safety Certification. 3. Which of the following steps is the last step in a strategy-based diagnostic process? a. Verifying the customer’s concern b. Researching possible faults c. Performing the repair d. Verifying the repair 4. When possible, which of the following is the best way to understand the customer’s concern? a. Asking the customer to guess the cause of the problem. b. Asking the customer to suggest a solution to the problem. c. Encouraging the customer to demonstrate the problem. d. Encouraging the customer to help you fix the problem. 5. The best way to address intermittent faults is to: a. look for symptoms, data, or DTCs that are repeatable or consistent. b. reverse the steps in the diagnostic process. c. ask the customer to bring back the vehicle when the fault occurs. d. take it up only when it is covered by warranty. 6. When the technician encounters a vehicle with more than one customer concern, and both originate from companion systems, the technician: a. should attempt to test for both faults at once. b. need not attempt to fix the second fault. c. should never choose those tests that might look at components of both systems. d. should isolate the faults and test them separately. 7. Choose the correct statement. a. When performing tests for an inspection under warranty, follow your intuition rather than the manufacturers’ guidelines. b. Researching possible faults should begin with a specific cause in mind. c. For hard parts, the best resource is frequently the respective dealership’s parts department. d. DTCs and freeze frame data need not be captured before clearing the memory. 8. All of the following will happen if the technician fails to document test results EXCEPT: a. The manufacturer will not pay the claim. b. The shop is out money for the parts and service. c. The technician will be unable to diagnose the fault. d. The technician will not be paid for his or her work. 9. All of the following statements with respect to the 3 Cs are true EXCEPT: a. Customer concern is documented on the repair order prior to the technician receiving the vehicle.

b. The second C in the 3 Cs refers to the cause of the customer’s concern. c. Technicians should note safety issues and maintenance items on the repair order. d. Additional service recommendations should never be documented on the repair order. 10. Which of the following is not one of the 3 Cs of vehicle repair? a. Cause b. Cost c. Concern d. Correction

ASE Technician A/Technician B Style Questions 1. Technician A says that when diagnosing a transmission problem, it is important to first verify the customer concern by taking the vehicle on a road test if possible. Technician B says that you should check for TSBs during the diagnostic process. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B 2. Technician A says that additional service recommendations should be documented on the repair order. Technician B says technicians are obligated to make the customer aware of safety concerns that require attention. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B 3. Technician A says the strategy-based diagnostic process is a scientific process of elimination. Technician B says the strategy-based diagnostic process begins with scanning the vehicle for DTCs. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B 4. Technician A says that manufacturers will often indicate what procedures are appropriate for their vehicles and components. Technician B says that the manufacturer’s service information can avoid premature failure of the repair. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B 5. Technician A says that technicians are frequently paid by the job, or flat rate, rather than paid hourly. Technician B says rushing the repair is best for the customer, so they get their vehicle back quickly. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B 6. Technician A says that it is only necessary for dealerships to check for updated parts and software/firmware before performing a repair. Technician B says that it is possible that manufacturers have become aware of a problem with a particular component or software version and have issued a software update. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B 7. Technician A says that the customer concern is the focus of step 1 of the diagnostic process. Often the concern is documented on the repair order prior to the technician receiving the vehicle. Technician B says the technician who works on the vehicle should take time to fully understand the

concern, read the repair order, and possibly talk further with the customer to understand the nature of the problem. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B 8. Technician A says that a repair order is only used in the shop and will be discarded when the vehicle is complete. Technician B says that the repair order is a legal document and could be used in a court. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B 9. Two technicians are discussing a transmission problem. Technician A says that it is important to test drive the vehicle because there may actually be no issue with the vehicle and the customer complaint is actually a normal operational characteristic of the transmission. Technician B says you should always check TSBs before performing any service of the transmission because the manufacturer may have updated a component. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B 10. Technician A says that experience will allow you to skip many of the steps of the diagnostic process because you will be familiar with the transmission. Technician B says that skipping steps of the diagnostic process can cause issues to be missed, or misdiagnosis of the problem. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B

© Jones & Bartlett Learning.

CHAPTER 2

Advanced Computerized Engine Control Diagnostics LEARNING OBJECTIVES After studying this chapter, you should be able to: 2-1

Analyze the basic strategy of ECM/PCM function.

2-2

Evaluate the use of powertrain control system diagrams.

2-3

Apply engine control service information to strategy-based diagnosis.

2-4

Perform initial module inspections.

YOU ARE THE AUTOMOTIVE TECHNICIAN A 2018 Ford F-150 is in for the check engine light ON. Which of the following are applicable and in what order as they apply to the diagnostic process? Verify the customer concern. Check for diagnostic trouble codes (DTCs). Check battery voltage. Review applicable service information for the DTC. Review data list input and output values. Review the wiring diagram. Research normal data parameters. Review freeze frame data. Check Mode 6 monitor data. An automotive technician is not someone who plugs in a code reader and then replaces a part. A technician applies their knowledge of engine performance using the strategic diagnostic process to isolate the cause of the DTC, make the repair, and then verify the vehicle is operating normally.

ECM/PCM Operation Review 2-1 Analyze the basic strategy of ECM/PCM function.

The engine control module (ECM) is sometimes called the powertrain control module (PCM), which has been covered in detail in MAST Automotive Engine Performance (FIGURE 2-1). This chapter builds on your knowledge of the following:

FIGURE 2-1 The PCM operates the engine and transmission based on input data from sensors and driver input. © Jones & Bartlett Learning.

ECM/PCM input operation ECM/PCM data processing ECM/PCM output control Driver actions and sensor data are inputs to the ECM/PCM. The driver using the ignition key or start button and depressing brake, throttle, and clutch pedals creates input signals from related switches and position sensors. The ECM/PCM processes these data using the following information (FIGURE 2-2):

FIGURE 2-2 The ECM processes data from sensor inputs to operate outputs, including the fuel and ignition systems. © Jones & Bartlett Learning.

Description Analog-to-digital converters vary voltage signals. Digital signals do not require the use of a converter circuit. Digital data are processed using logic gate technology, data look-up tables, and data mapping. Outputs are controlled based on commands from the processor.

ECM/PCM Data Processing Technicians are not expected to be electrical or software engineers, but it is important that you understand the input-process-output of the PCM. When there is an engine performance–related customer concern, you need to be able to combine system operation knowledge with the service

information, scan tool data, digital multimeter (DMM), oscilloscope readings, and any other tools required to isolate the cause of the customer concern correctly. For example, the customer states that the vehicle hesitates when accelerating to pass on the highway. The advanced engine performance technician is immediately going to understand that this concern could be related to the following: Throttle input data Fuel pressure Injector operation Ignition operation Mass airflow/manifold absolute pressure (MAF/MAP) False/unmetered air Out-of-range sensor input data Battery voltage issues Excessive circuit voltage drops Hybrid system integration The advanced engine performance technician knows this from their study of the system through training and work experience. Understanding how the ECM/PCM processes data and what inputs or outputs and other systems could create this concern allows the technician to integrate the strategy-based diagnostic process seamlessly. Data processing for our use will cover three areas: logic gates, look-up tables, and data mapping. Engine control unit (ECU) processors incorporate logic gates. A logic gate is an electronic component that reacts to the zeros and ones. Logic gates are an essential part of the building blocks of integrated processing circuits. There are seven basic types of logic gates, and these can be combined, much like you combine letters to form words, to create additional functions (FIGURE 2-3).

FIGURE 2-3 Logic gates are the basis for digital programming. © Jones & Bartlett Learning.

Description Each logic gate is based on a truth table. The truth table shows the input on the left, and if there is more than one column, each column represents the possible input. For our examples, a 0 is a low input or output (usually an OFF signal), and the 1 is a high signal (usually an ON signal). The most basic logic gate is the NOT logic gate. This gate produces the opposite outcome of the input. If the input is ON, the output is OFF, for example. The AND gate requires that both inputs be the same to produce the related output. For example, if A and B are both 1, then the output will be 1; the logic gate requires a high signal at A and B to output a high signal. The NAND gate functions in the opposite fashion of the AND gate. The output signal is always high unless both inputs are high. The OR gate outputs a high signal if any input signal is high, so that if A is high or B is high, the output is a high signal. The NOR gate is the opposite of the OR gate. The NOR gate outputs a high signal only when both signals are low. Any time there is a high input signal there is a low output signal. The XOR gate will output a high signal only if one input signal is high. If both are low, or if both are high, it outputs a low signal. The XNOR gate is the opposite of the XOR gate. It outputs a high signal if both inputs are the same and a low signal if only one input is high. TECHNICIAN TIP Although technicians do not repair components inside ECUs, it is helpful to understand what is going on there. Your ability to diagnose ECU controlled circuit concerns is enhanced by knowing how the ECU processes input data and what type of ECU output drivers may be used to provide a correct response—whether it is operating the heating, ventilation, and air-conditioning (HVAC) blower motor at the desired speed, controlling vehicle acceleration via an internal combustion engine throttle control, or viewing the motor current data for an electric or hybrid-electric vehicle. If this subject matter entices you to learn more, the automotive industry is always searching for qualified electrical engineers and computer programmers. A technician who furthers their career to achieve a degree in these fields is a valuable resource to a manufacturer’s research and development staff. Technicians know how systems work, how they can fail, and what it takes to repair them. That knowledge combined with a four-year degree in engineering can lead to many opportunities and advance your career.

Here we will review the basic operation of a logic gate for the stop light switch, which is an input to the ECM/PCM (FIGURE 2-4).

FIGURE 2-4 The brake light switch input data are processed using logic gates. © Snap-on Incorporated.

Refer to the wiring diagram for the stop light switch. The ECM is monitoring for a stop signal and a start signal (ST-1). These inputs are used for push button engine start in this example. The stop light signal input is as follows: Brake pedal not applied: ECM pin 11: 0 V, ECM pin 24 Source V Brake pedal applied: ECM pin 11: Source V, ECM pin 24, 0 V A logic gate is used for each of these input signals to process these voltage signals. Note that these are digital signals, as they are either 0 V or Source V. The logic gate is an electronic component that is engineered to turn ON or OFF based on input status. For this circuit, the logic gate will turn ON when the two input voltages indicate the brake pedal is applied by the driver providing source voltage at ECM pin 11 and 0 V at pin 24. For this reason, it is called an AND gate because there must be source voltage at input pin 11 of Source V “and” 0 V at pin 24, which indicates the brake pedal is applied. If there is an open circuit on either wire between the stop light switch and the ECM, the logic gate will not respond and the engine will not start. Data look-up tables are used for inputs with varying data, including varying voltage and varying frequency (TABLE 2-1). A sample look-up table is shown for an engine coolant temperature (ECT) sensor. The voltage values correspond to a temperature. The ECM processor is able to convert the ECT signal voltage into temperature data. The data can then be used by the processor for several functions, including turning on the cooling fan, adjusting the air-fuel ratio, and for ignition timing. Speed sensor data may also use look-up tables, where the number of pulses from the sensor are converted to hertz (cycles per second) and the frequency values correspond on the data look-up table to vehicle or engine speed. TABLE 2-1 Data Look-Up Tables—Temperature Collection

Description Data maps are used in the ECM processor and often use more than one input to control an output device. Let’s look at the fuel system data map as an example (FIGURE 2-5). Several ECM inputs are used to create engine load, including throttle position, engine speed, and air intake volume (MAF or MAP). The ECM uses the data map to take all this data and in a few milliseconds adjust fuel injector ontime so the correct air-fuel ratio is achieved for the current engine operating condition. The air-fuel ratio sensor input is used to fine-tune the injector on-time programmed on the fuel map, allowing for corrections due to weather, driver input, and mechanical variation in components. Data maps are almost always used for fuel injector on-time and ignition timing. Data maps may also be used to control variable valve timing, electronic exhaust gas recirculation (EGR) control, purge control valves, and more.

FIGURE 2-5 Data maps allow the ECM processor to use multiple inputs to effect control of an output device.

Description

Power Train Control System Diagram 2-2 Evaluate the use of powertrain control system diagrams.

Many manufacturers use an overall system diagram of the PCM and related components. The engine control system diagram is located in the service information (FIGURE 2-6). The system diagram provides a quick overview of engine control sensor inputs, actuator outputs, and how they are electrically connected to other components and the control module. There may be variation of diagram design and in the type of information they include.

FIGURE 2-6 The engine control system diagram provides a quick overview of the inputs, outputs, and wiring layout. © Snap-on Incorporated.

At first glance you may think the system diagram is a basic wiring diagram. They are similar, but each has a purpose. The system diagram usually offers a vertical layout that shows the control module in the center with various inputs and outputs shown on the left and right sides. It also is more compact than the engine control system wiring diagram so it can save you time when determining how various components are electrically connected to the control module or to other components, such as fuses and relays. If you need to do a cranking compression test, you can use the system diagram to quickly determine which fuse to remove to disable the fuel injectors or fuel pump so there is no fuel entering the cylinders during your testing. The system diagram also shows which fuse or fuses are related to various subcircuits, such as the air-fuel ratio or oxygen sensor heater circuits (FIGURE 2-7).

FIGURE 2-7 The system diagram allows you to see which components supply source voltage to a component, such as the airfuel ratio sensor heater. © Jones & Bartlett Learning.

Description Let’s take a closer look at a small section of the engine control system diagram. Your ability to recognize electrical symbols now has an application from your electrical course work. You should notice the ground symbols (1), relay (EFI Main #2), splice point (2), and wiring shield (3). The diagram shows the electronic fuel injection (EFI) main number 2 relay control source voltage to the heater elements in the air-fuel ratio and oxygen sensors. The fuse is common to both heaters. A blown fuse will cause DTCs to store for the oxygen sensor and air-fuel ratio sensor heater circuit operation. Referring to the system diagram, you can quickly note what is common to both circuits—the fuse and the relay. This knowledge, along with the DTC diagnostics, can help you begin to develop a diagnostic plan. Here you may begin by verifying fuse condition; if it appears okay, is there source voltage on each side of the fuse test points (the small holes on the top side of the fuse)? If the fuse is okay, you can then perform applicable relay tests to determine if the relay and related circuit wiring is okay or has a fault. Notice that this sample diagram uses identifiers you may not be familiar with. The Society of Automotive Engineers (ASE) and vehicle manufacturers use standardized nomenclature in most service information. There will be exceptions, and there are a few here. The crankshaft position (CKP) sensor in this sample is a two-wire alternating current generating type. This manufacturer designates the sensor signal output as NE+ and NE– (NE plus and NE minus) for the positive and negative sine wave voltage that is created.

Sensor operation is covered in detail throughout this text. Your understanding of the various sensors is critical for accurate component testing and diagnosing the cause of a fault. Learning the various manufacturers’ nomenclature will be helpful if you work in a dealer service environment. This will occur naturally as you use the service information over time, along with attending the manufacturers’ training course offerings and completing web-based course work. Technicians in an independent environment will interact with several different sets of nomenclature. Using the system diagrams from different manufacturers will show that what really matters is your understanding of component operation and overall electrical diagram interpretation ability. The manufacturers’ nomenclature will not have much, if any, effect on your ability to diagnose an engine control related fault. The ASE L1 certification test composite vehicle electrical diagram is similar to the engine control system diagram, showing the layout of components along with ECM pin numbers. This diagram is referenced extensively in the L1 certification questions (FIGURE 2-8). Using the system diagram on a regular basis not only assists each engine control fault diagnosis, but also prepares you for passing the L1 certification test.

FIGURE 2-8 The ASE L1 Advanced Engine Performance composite vehicle diagram is very similar to the system diagram. © National Institute for Automotive Service Excellence (ASE).

Engine Control Service Information 2-3 Apply engine control service information to strategy-based diagnosis.

Engine control service information supports Step 2 of the strategy-based diagnostic process: Researching possible faults and gathering information. This information includes the following: Technical service bulletins Diagnostic trouble code information No code diagnosis problem symptom tables ECM/PCM terminal ID and related signal values Engine control intermittent fault check procedures

Engine Control Technical Service Bulletins Technical service bulletins (TSBs) provide a repair path for known vehicle conditions that may be caused by a faulty component, installation procedure, or software (FIGURE 2-9). A TSB may be triggered by a part manufacturer discovering that a batch of components is possibly defective, an assembly line procedure was not followed or needs to be amended, or ECM software has been updated to correct a drivability issue, such as vehicle hesitation. Verify the customer concern. With it verified, check for any TSBs that may apply to the concern. Follow TSB procedures if the vehicle concern and related production data or vehicle identification number (VIN) falls within the TSB coverage parameters. If you bypass checking for TSBs, you may spend a great deal of time diagnosing a concern that has already been diagnosed by the manufacturer and has a defined repair. Because this is a known condition with a known repair procedure, you will most likely only be paid for the TSB repair flat-rate time even if your diagnosis took longer.

FIGURE 2-9 TSBs provide a procedure to correct a known vehicle condition. © Snap-on Incorporated.

Engine Control Diagnostic Trouble Code Service Information Diagnostic trouble codes usually illuminate the check engine light (malfunction indicator light [MIL]). You will have to use a scan tool to retrieve the DTC and then obtain the related service information (FIGURE 2-10). This information is often referred to as advanced diagnostics and includes the following:

FIGURE 2-10 The DTC diagnostics provide the information required to diagnose the DTC. © Snap-on Incorporated.

DTC description How the DTC sets What can cause the DTC to set Data list parameters Monitor description and strategy Enabling conditions Malfunction thresholds Component operating range Applicable drive cycle Applicable wiring diagram Inspection procedure This information supports your diagnosis when a DTC has set. The advanced engine performance technician understands that an ECT sensor code does not translate to the action of going to the parts department for a new sensor. This technician reviews the information to determine what type of fault caused the DTC to store. For example, is there an open or short circuit, is data out of range, how does the ECM monitor this component or system, and what conditions must be met for the monitor to run?

Other factors include the component’s normal operating range and whether a drive cycle is associated with the component or system monitor. These topics are covered in detail in later chapters of this text. Some DTC information will include a simplified wiring diagram of the affected circuit (FIGURE 2-11). This diagram may show more detail of the component and internal ECM circuit than the full system wiring diagram.

FIGURE 2-11 Some DTC information will include a component- or system-specific wiring diagram. © Snap-on Incorporated.

Description The DTC inspection procedure is usually laid out as a step-by-step path for the technician (FIGURE 2-12). The procedure describes each test you need to perform; then, based on the results, it provides a path to the next step. In the example shown, you access the scan tool data list and observe the ECT parameter identification (PID) readings. Based on the result, you are then directed to other procedures to continue inspection and testing.

FIGURE 2-12 The DTC inspection procedure provides step-by-step diagnostic actions to isolate the cause of the fault. © Snap-on Incorporated.

Description

Engine Control Diagnostic No DTC Diagnostics The majority of engine performance faults set a related DTC. With a DTC, you have a diagnostic process to follow. Engine performance concerns that do not set a related DTC may at first seem very difficult to diagnose. Use of the diagnosis by symptom information provides direction for your diagnosis (FIGURE 213). Locate the applicable description of the symptom in the service information—for example, engine cranks but does not start (Hard/No Start/Restart). The service information provides a list of possible causes for this concern. They are usually listed from most likely to least likely. Begin with what you feel is the most likely based on your initial evaluation, any other symptoms, and any scan tool data that help you isolate a possible cause.

FIGURE 2-13 Engine performance concerns without a related DTC can be diagnosed through the assistance of the diagnosis by symptoms service information. © Snap-on Incorporated.

Description For example, the CKP sensor circuit is listed as a possible cause of a no start. The electronic service information provides a link to inspecting the sensor (FIGURE 2-14). Note that as your knowledge of system and component operation expands from your work in the course this text supports, you will recognize that the service information may assume you have done some diagnostic work before getting to a component test like this example. This may have included a spark test or noting engine revolutions per minute (rpm) on the scan tool data list during engine cranking.

FIGURE 2-14 The symptoms information provides links to inspect components or systems that are related to the concern. © Snap-on Incorporated.

Description

Engine Control ECM/PCM Terminal ID and Related Signal Values The ECM/PCM terminal data in the service information are very helpful for your diagnosis (FIGURE 215). The data are usually laid out in table format and include the terminal number and the related wire color, which is very helpful to ensure you have identified the correct terminal for your testing. The table also identifies what the terminal is for, what test condition you should set for testing (engine ON and at idle speed, for example), and data value specifications for that terminal. For example, testing at terminal A25-37 for ignition switch input signal, the ignition must be ON and the voltage should be between 11 and 14 V. If the reading is near 0 V, there may be an open circuit. If it is less than 11 V, there may be resistance in the harness. Use of this information is valuable, as this is a quick way to determine what your test voltage should be and whether you are testing at the control module or at the other end of the wire that attaches to the input or output component.

FIGURE 2-15 The terminals of the ECM chart provide information that is critical when testing for proper signal, voltage, or resistance at the control module. © Snap-on Incorporated.

Description

Engine Control Intermittent Fault Check Procedures Intermittent faults are the most difficult to diagnose if the concern is not occurring when you attempt to verify it. The service information may offer assistance (FIGURE 2-16). Some scan tools offer a function (check mode in this example) that puts the ECM into a mode that narrows the time and out-of-range values normally required to set a DTC. Follow the procedure to use this mode, perform the recommended drive cycle, and note any DTCs that set. With a DTC now stored, you can begin diagnosis. If no DTC stores, you must refer to the problem’s symptoms information for a list of possible causes.

FIGURE 2-16 The service information may provide one or more processes for dealing with intermittent engine performance faults. © Snap-on Incorporated.

Description From the problem’s symptoms table, you can also use a method to check harness connections and components (FIGURE 2-17). Some manufacturers even offer a scan tool test, sometimes called a wiggle test, for this method. Wiggle harness connections at input and output components and the PCM. Gently tap on components with your finger and note if the scan tool sets a pending or current DTC or the scan tool outputs a signal that a circuit fault was detected. You may also be directed to do water tests or heat tests with a heat gun to simulate high heat or very wet conditions that may cause the fault.

FIGURE 2-17 Intermittent faults may require component manipulation, such as a light tap with your finger or a gentle wiggle of the harness connector to attempt to duplicate the fault. © Snap-on Incorporated.

Description

Engine Control Wiring Diagram The engine control wiring diagram is usually several pages due to the number of sensor inputs, actuator outputs, junction box components, vehicle network connections, and complex wiring harness (FIGURE 218). The wiring diagram may be in color and provides ECM and component pin numbers, connector identification, and ground identification. Many manufacturer service information systems offer interactive diagrams that can link you to component location and other relevant service information. Use the diagram to identify the function of each pin at a component or at the ECM, including which is the signal and which has voltage or a ground. Use the electrical diagram in conjunction with DTC or problem symptom diagnostic procedures.

FIGURE 2-18 The engine control wiring diagram will be several pages long due to the number of system components. © Jones & Bartlett Learning.

Engine Control Module Inspection 2-4 Perform initial module inspections.

The engine or powertrain control module is housed under the hood of most vehicles in a strong weatherproof aluminum case (FIGURE 2-19). There are usually two or more weather pack female harness connectors that lock into the PCM male connectors. Some older vehicles used a bolt in the harness connector that secured it to the PCM.

FIGURE 2-19 The PCM is usually located under the hood. The harness connectors lock into the PCM so they cannot vibrate loose. © Jones & Bartlett Learning.

There is often an information sticker on the PCM that may include the basic part and calibration numbers (FIGURE 2-20). This information should not be overlooked, especially if a vehicle is towed in as a no-start, it runs but will not idle, or it has numerous DTCs. A customer may not realize that even though a PCM will connect to the harness, internal hardware may not be correct for the vehicle, or an incorrect software calibration will prevent normal operation.

FIGURE 2-20 Most PCMs have a decal that includes the basic part number and vehicle calibration. © Jones & Bartlett Learning.

The PCM communicates with the scan tool through the 16-pin data link connector (FIGURE 2-21). The scan tool can usually display the PCM calibration or software level identification, and this should be verified as part of engine performance diagnosis. Installation of an incorrect control unit, incorrect software programming, or the software requiring an update can all be quickly determined using the scan tool. The wrong control unit may be installed after a collision repair or someone may have attempted to resolve a problem by installing a used or remanufactured unit. These conditions require the correct control unit be installed and the most current software be uploaded (sometimes called a software reflash) with the scan tool. If you note a software update is available, review the related service bulletin that supports the update to determine if the action is required for all vehicles or only vehicles with a specific customer concern or specific powertrain or option package. Perform a software upload or update following the procedures detailed in the service information. This usually includes the following:

FIGURE 2-21 The PCM communicates with the scan tool through the 16-pin data link connector usually located near the steering column. © Jones & Bartlett Learning.

Connect a smart battery charger to the vehicle to maintain full battery voltage during the procedure. Connect the scan tool and establish communication with the powertrain control module. Follow scan tool screen prompts to erase the current software programming. Follow scan tool screen prompts to upload the applicable software programming. Verify the software update identification is correct after the upload completes. Perform a test drive and verify the vehicle operates normally and no DTCs are set by performing a DTC check after your test drive. TECHNICIAN TIP It is critical that once the software upload is started it is not interrupted. A vehicle battery that discharges during the upload or someone turning the ignition OFF or disconnecting the scan tool will interrupt the upload and can render the PCM unusable, as you will no longer be able to use the scan tool to connect to it.

The control module is very robust and rarely fails. A control module may fail due to the following: It is damaged during a collision event. A vehicle is involved in a flood or is submerged in water. A technician does not follow powertrain circuit testing procedures and damages internal control module circuits. A shorted output component can increase current load on the electronic components inside the

module, including transistors, causing them to fail open or shorted. An output device that cannot be turned ON (or OFF) with the scan tool active test or through normal engine operation, such as an ignition coil or fuel injector, may indicate there is a failed output driver. TECHNICIAN TIP If the control module no longer operates an output device, it is recommended that the related output device also be replaced. Many output devices are inductors, which may test fine at room temperature but fail shorted as engine temperature increases to normal range. Failure to replace a faulty output device will lead to a failure in the replacement control module. Most manufacturers recommend doing this, and they may not cover any costs if the control module fails if the related output component was not replaced.

Before condemning any control module, verify that the PCM has proper voltage from all pins that provide battery voltage. Verify that grounds are connected and have less than a 50-mV drop on them when the engine is running. (If the engine will not run, do the test with the ignition ON, as voltage cannot drop without current present.) Only recommend replacing an ECM after performing these and any diagnostic specific tests you have followed in the service information. To verify PCM software calibration, follow the steps in SKILL DRILL 2-1. SKILL DRILL 2-1 Verifying PCM Software Calibration 1. Connect the scan tool to your assigned vehicle. 2. Turn the ignition ON, engine OFF. a. Tech Note: It is often a good idea to have a smart battery charger connected to the vehicle while performing Key On Engine Off tests. This keeps the battery at full charge while using the scan tool to check for vehicle information, DTCs, and PID data and to monitor test results. 3. Enter the vehicle information required for scan tool communication (this will vary based on model year and scan tool type). 4. Access the vehicle powertrain system from the scan tool menu. 5. With communication established, select the software calibration ID from the menu. On some vehicles this may appear as part of the scan tool to PCM handshake process. 6. Write down the calibration number on a notepad or lab sheet (if not done so already, you may also need the vehicle model year [MY], production date, and engine size/code). Access the related service information for your assigned vehicle and verify that this is the correct calibration for the vehicle.

WRAP-UP Ready for Review The engine control module may be abbreviated ECM or PCM, for powertrain control module. The ECM functions by monitoring data input, processing the data, and providing output commands. The ECM uses logic gates, look-up tables, and data maps to process input signals to determine what output signals are required. ECM system diagrams provide a quick overview of the inputs and outputs used in a vehicle’s engine management system, along with a simplified wiring diagram of the related components. Service information is integral to the strategy-based diagnostic process and offers information on DTCs, diagnosing by symptom, ECM terminal ID and related voltage or signal values, and diagnosis of intermittent faults. The engine control wiring diagram is almost always required during engine performance diagnosis and provides wire color, pin ID, connector ID, and component locations as well as source and ground paths. Control module failures are not common. Always verify control module voltage source values and that grounds are all functioning with a voltage drop less than 50 mV. Replacing an ECM due to an output drive failure usually also requires replacing the related output device. A new ECM will usually require a reflash to link with the vehicle VIN and other data, along with uploading the engine control software.

Key Terms Data maps Specifications that have been set by the original equipment manufacturer (OEM) per sensor, which allows the PCM to make decisions based on sensor outputs. Engine control module (ECM) Computer that operates the fuel and ignition systems on later model vehicles. Logic gates An electronic component that reacts to the zeros and ones. ECU processors incorporate logic gates. Powertrain control module (PCM) Computer that operates the fuel and ignition systems on later model vehicles. Service information Vehicle repair information that is available for the technician to repair the vehicle. Smart battery charger A microprocessor-controlled battery charger that can be used to charge various types of batteries without overcharging them. Technical service bulletin (TSB) Information issued by a manufacturer to alert technicians of expected problems or changes to repair procedures.

Review Questions 1. Multiple input data mapping is used for all of the following output controls EXCEPT: a. ignition timing. b. fuel injector on-time duration. c. VVT cam position. d. fuel pump relay. 2. Refer to the system diagram shown below. The fuel injectors receive source voltage through which of the following? a. IG2 b. C/OPN c. EFI Main d. ECU-IG2 #3 Fuse

Description © Jones & Bartlett Learning

3. Refer to the diagram shown below. EFI fuse #3 provides source voltage to how many components on this portion of the system diagram? a. 1 b. 2 c. 3 d. 4

Description © Jones & Bartlett Learning

4. Based on the table below, which statement is correct? a. Accelerator pedal position output signal voltage is 2.8 V when the pedal is fully depressed. b. Injectors operate at a steady 11 to 14 V with the engine running. c. There are two APS sensor signals. d. A/F sensor heater voltage is 11 to 14 V with the engine running.

Description © Jones & Bartlett Learning

5. All of the following are usually part of the DTC diagnostics, EXCEPT: a. ECM/PCM wiring diagram. b. DTC description. c. monitor strategy. d. enabling conditions. 6. The service information offers all of the following for engine performance diagnostics, EXCEPT: a. sensor waveform data. b. network waveform data. c. detailed instructions on using the DMM for component testing.

d. how to access factory scan tool functions using the applicable menu icons. 7. According to the diagram below, you can disable the fuel pump to perform a compression test by removing which fuse? a. 20A EFI Main #2 b. 7.5A Inj c. 7.5A EFI #3 d. 7.5A ECI-IG2 #1

© Jones & Bartlett Learning

8. Refer to the purge vacuum switching valve (VSV) diagram shown below. Is this solenoid source or ground controlled? a. Source controlled b. Ground controlled c. It is source controlled during evaporative emission (EVAP) purge operation. d. The purge VSV has a floating ground through the inductive windings.

© Jones & Bartlett Learning

9. Which of the following can cause an ECM failure? a. A short to ground on the ECT signal wire b. A short to ground on the CKP sensor signal wire c. An open ground in the ECM voltage supply circuit d. A short in the #3 injector coil 10. Connect the digital storage oscilloscope (DSO) to the ignition coil __________ to view the ECM control signal. a. primary source voltage b. secondary voltage c. primary ground voltage d. It is not possible to view this signal on COP systems.

ASE Technician A/Technician B Style Questions 1. Technician A says ECM fuel and ignition data maps rely only on the CKP sensor to control injector on-time and ignition timing. Technician B says most ECM outputs rely on data map–based output control. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B 2. Refer to the wiring diagram shown on the next page. Technician A says relays are usually controlled using duty cycle output control. Technician B says the fuel pump for this vehicle is duty cycled to control fuel pressure for varying engine loads. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B

© Jones & Bartlett Learning

3. Technician A says the ECM system diagram shows circuit details for input and output components. Technician B says the ECM system diagram is the best source to locate connector pin number and location. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B

4.

5.

6.

7.

8.

d. Neither Technician A nor Technician B Technician A says the service information includes details on PID data, including expected voltages that can help you when testing a component or viewing data on the scan tool. Technician B says enable criteria defines what is required for a component monitor to run. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B A vehicle is in the shop for a check engine light ON concern. The check engine light is currently OFF when the engine is running. Technician A says the malfunction threshold for the component has been exceeded, resulting in a DTC storing. Technician B says the service information provides a list of DTCs that can prevent a monitor from running. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B Technician A says enabling conditions, which must be met for a monitor to run, are listed as part of the wiring diagram. Technician B says any DTC will prevent the component and system monitors from running. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B Technician A says the engine control system wiring diagram shows the shared sensor ground points. Technician B says the engine control system wiring diagram has printed text that informs you which wire or wires to test for measuring duty cycle, frequency, or connecting a DSO to interpret input or output signals. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B Refer to the diagram shown below. Technician A says this diagram is usually found with the DTC diagnostics of the service information. Technician B says the EFI relay supplies source voltage to the MAF sensor. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B

© Jones & Bartlett Learning

9. Refer to the diagram shown below. The ECM will not communicate with the scan tool. Technician A states 0 V at pin 16 is normal. Technician B says checking pins 6 and 14 with a DMM and noting 83 Ω indicates the ECM is faulty and should be replaced. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B

Description © Jones & Bartlett Learning

10. Technician A says the check engine light is ground controlled by the ECM. Technician B says the IG2 relay is turned only when source voltage is supplied by the ignition switch or smart key ECU. Considering the diagram below, who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B

Description © Jones & Bartlett Learning

© Jones & Bartlett Learning.

CHAPTER 3

Port Fuel Injection System Diagnosis LEARNING OBJECTIVES After studying this chapter, you should be able to: 3-1

Describe port fuel injection (PFI) systems and their function.

3-2

Apply service information to PFI diagnosis.

3-3

Examine PFI service procedures.

3-4

Employ PFI fuel pump testing procedures.

3-5

Inspect switched inputs.

3-6

Inspect temperature sensors.

3-7

Inspect position sensors.

3-8

Inspect pressure and mass airflow sensors.

YOU ARE THE AUTOMOTIVE TECHNICIAN A 2018 Nissan Altima 4 cylinder is in for the check engine light ON and DTC P0171 fuel system lean. Which of the following are applicable and in what order as they apply to the diagnostic process? Verify the customer concern. Check for DTCs. Check battery voltage. Review applicable service information for the DTCs. Review data list input and output values. Review the wiring diagram. Look up normal data parameters. Review freeze frame data. Check the Mode 6 monitor data. Check air-fuel ratio sensor operation. Inspect for exhaust leaks ahead of the air-fuel ratio sensor. Check the fuel pressure. Inspect the MAF sensor. The technician’s knowledge of what may cause a fuel delivery–related concern is demonstrated by applying strategy-based diagnostics. It is this knowledge that allows the master diagnostic technician to make a mental list of the potential causes of a lean condition, in this case. This knowledge saves time, allowing for a very focused visual inspection, quick determination of which scan tool data list items to scrutinize, and easier plan development during transition to the testing phase of the strategic diagnostic process.

Port Fuel Injection Component Review 3-1 Describe port fuel injection (PFI) systems and their function.

The port fuel injection (PFI) system components include the following (FIGURE 3-1):

FIGURE 3-1 The PFI system includes the fuel pump, fuel injectors, PCM, and related input sensors.

© Jones & Bartlett Learning

Description Powertrain control module (PCM) Inputs to support fuel control Intake air temperature (IAT) and engine coolant temperature (ECT) Crankshaft position (CKP) sensor and cam position (CMP) sensor Accelerator position sensor (APS)/throttle position sensor (TPS) Mass airflow (MAF) or manifold absolute pressure (MAP) Air-fuel (AF) ratio sensor Fuel pump Fuel injectors Relays The PCM monitors sensor input data and uses fuel data mapping to determine injector pulse width (on-time) to deliver the necessary amount of fuel. The longer the fuel injector on-time, the greater the amount of fuel that is delivered. The PCM monitors engine load based on the following high-authority inputs: Engine rpm from the crankshaft position sensor Engine coolant temperature Engine load derived from throttle position and either MAF amount or MAP The fuel delivery is fine-tuned based on feedback from the AF ratio sensor. The PCM sets a target AF ratio based on the high-authority inputs listed previously, and the amount of oxygen in the exhaust ahead of the primary catalysts is measured in the form of a small voltage and circuit current from the AF sensor. A higher level of oxygen in the exhaust indicates the mixture is leaner than the target, and a lower level of oxygen indicates the mixture is richer than the target. The PCM has the ability to adapt to conditions that set a baseline for the target air-fuel ratio. This adaptability is called fuel trim. The long-term fuel trim (LTFT) indicates the amount, usually in a percentage, that the PCM has adapted from the baseline fuel data map. The PCM usually controls one or more relays or communicates with a fuel pump control module to operate the fuel pump. The fuel pump provides pressurized fuel to the fuel injectors within a specified pressure and volume. The fuel injectors for most PFI systems are inductive devices. The injector uses magnetism to lift a pintle off its seat, which allows fuel to pass through and form very small fuel droplets that are then drawn into the related engine cylinder on the intake stroke (FIGURE 3-2). Various injector designs have been used to atomize (break into very small droplets so it can vaporize in the cylinder) the liquid fuel. Remember, liquid gasoline will not burn. It must turn into a vapor and mix with oxygen in the air intake charge to create the combustible mixture that burns during the power stroke.

FIGURE 3-2 The fuel injector is an inductive device that uses magnetism to lift the metering needle and allow pressurized fuel to atomize as it enters the engine. © Jones & Bartlett Learning.

Description TECHNICIAN TIP Fuel injectors are selected for their flow rate and atomization properties for the engines in which they are used. Fuel injectors may look the same but can have different flow rates and spray patterns. Some injectors are color coded to avoid confusion during fuel rail assembly and service. Installing one or more incorrect fuel injectors has perplexed many technicians when the engine fails to run correctly after installation.

The PCM controls injector on-time using a transistor for each injector, usually on the ground side of the circuit. Input sensor data are processed by the PCM. The PCM plots the data on the fuel map to then turn on the injector transistor (often called a driver circuit) for a set amount of on-time. The longer the ontime, the more fuel that is delivered to the related cylinder. On-time increases as engine load and rpm increase because more air is entering the engine, so more fuel is required to maintain the correct air-fuel ratio. The fuel map is unable to account for mechanical variations, fuel variations, and weather factors, such as humidity, that can affect the air-fuel ratio. Also, the catalyst requires the AF ratio to be within a narrow range to maximize emission control, and excess fuel use also reduces fuel mileage. Data from an AF ratio sensor provides feedback on how well the injector on-time is meeting engine power demands. A leaner than normal AF ratio will cause the PCM to increase injector on-time. A richer than normal AF ratio will result in less injector on-time. The technician can monitor all of this using the scan tool. Data list items include the following: Injector on-time, usually displayed in milliseconds (ms) Target air-fuel ratio Actual air-fuel ratio AF sensor voltage AF sensor current Long-term fuel trim

Short-term fuel trim Some of this may be new to you, and this content will be covered in detail in applicable modules. For now, it is important to recognize that the fuel system operates as follows: The fuel pump delivers fuel at the appropriate pressure. The PCM processes input data to determine the injector on-time based on the fuel data map. The PCM sets a target air-fuel ratio based on overall engine operating conditions. The air-fuel ratio sensor data are used by the PCM to fine-tune the injector on-time to meet the target air-fuel ratio. Long-term fuel trim indicates how the PCM has adapted injector on-time to various conditions, including mechanical variations, component aging, and weather conditions over a period of time (a value of 3% indicates that the PCM is increasing on-time from the fuel map by 3%). Short-term fuel trim (STFT) indicates how the PCM is adjusting injector on-time at that moment in time. (A value of -7% indicates that the PCM is decreasing injector on-time based on the 3% longterm adjustment. Total adjustment is calculated by adding short and long term together, in this case 3% + -7% = 4% total fuel trim.) Several input sensors provide data that allow the PCM to adjust fuel delivery to the engine. As stated, high authority sensors include the following: ECT Engine speed (from the CKP sensor) Engine load calculation from the TPS and MAF or MAP Low-authority sensors provide additional data for the PCM to calculate the fuel injector on-time, and include the following: IAT CMP APS IAT/ECT sensors compensate for very cold or hot ambient air and for the temperature of the engine. A cold engine requires more fuel (a richer mixture) to start and run, as gasoline does not vaporize very well at cold temperatures. The CKP/CMP sensors provide data on engine speed and what cylinder is on the intake stroke, so the fuel injectors can be operated for each cylinder as the intake valve is opening. The APS/TPS sensors provide data on how aggressive the throttle is being opened, which requires a burst of fuel to prevent a hesitation and to allow full power for acceleration or fuel cut on deceleration when the throttle rapidly closes. Intake air is measured directly using a MAF sensor or calculated based on engine speed and the use of a MAP sensor. The air-fuel ratio sensor provides feedback to the PCM on how well the fuel delivered was burned in the engine. This allows the PCM to add or subtract fuel by controlling injector on-time to achieve the desired air-fuel ratio. Technicians can view AF ratio adjustments using the fuel trim data along with all input and output data on the scan tool.

PFI Service Information 3-2 Apply service information to PFI diagnosis.

Diagnosis of PFI system–related faults relies on your efficient and thorough use of applicable service information. Most manufacturer and aftermarket service information sites include DTC diagnostics, fuel system component diagnosis, and related component replacement procedures. PFI–related DTCs are designated by the number 1 or 2 in the third alphanumeric position of the code (FIGURE 3-3).

FIGURE 3-3 PFI-related DTCs are usually designated by the number 1 or 2 in the third character position. © Jones & Bartlett Learning.

Description

PFI Wiring Diagram The service information includes inspection procedures for PFI components that may not directly set a DTC, such as the fuel pump and the fuel injectors. Like the DTC inspection procedure, follow each step and perform the related action accurately. Some inspection procedures may include a system wiring diagram to assist your testing, though it may still be necessary to use the applicable wiring diagram information to determine wire color and connector locations. The procedures usually show you how to test the component and the normal test values (FIGURE 3-4).

FIGURE 3-4 The service information shows how to test PFI-related components. © Snap-on Incorporated.

Description The example shows measuring resistance of the fuel injector between pins 1 and 2. The injector should show 11.6 to 12.4 Ω at 68oF. The service information includes removal and installation procedures (FIGURE 3-5). Note that some steps may have a link to perform the related task, which includes a separate list of steps for that one component.

FIGURE 3-5 Service information includes step-by-step component removal and installation procedures. © Snap-on Incorporated.

Description The PCM wiring diagram is integral to almost every diagnostic process of the PFI system. The portion of the diagram shown in FIGURE 3-6 includes the fuel pump and fuel injector circuits. The diagram identifies wire colors, pin and connector numbers, source voltage wiring, ground points, and current paths. Most manufacturer wiring diagrams offer interactive diagrams where you can select a wiring component, such as the fuel pump or fuel pump ground, to show details such as location.

FIGURE 3-6 The wiring diagram offers locations for components, connectors, and ground points. © Snap-on Incorporated.

Description Selecting the ground fuel pump ground links to the diagram showing the ground location on the vehicle. Using non-OE (original equipment) service information systems may require you to access component location diagrams from a menu of the various diagrams available. Use the wiring diagram and wiring component location diagrams as part of your strategy-based diagnostic process. To use a fuel injection wiring diagram, follow the steps in SKILL DRILL 3-1. It is recommended practice to highlight the current paths for the related part of the diagram you are using. Note the predicted voltage values on the diagram, and then as you do each test, note the actual value observed on the diagram. SKILL DRILL 3-1 Using a Fuel Injection Wiring Diagram

Description 1. Use the service information to locate and print the port fuel injection wiring diagram for your assigned vehicle.

2. Trace the path from the battery source voltage to the fuel injectors using your orange highlighter.

3. Trace the ground path for each injector using your green highlighter. Note that each injector has a different ground path to the PCM. This indicates that the injector circuit is ground controlled.

Description 4. Trace the path from the battery source voltage to the fuel pump using the orange highlighter, and note any components that are used, including fuses, relays, and possibly a fuel pump control module.

5. Trace the fuel pump circuit grounds in blue, including the fuel pump and relay(s). Note whether the relay(s) are source or ground controlled on your diagram. 6. Understanding the complete circuit on the wiring diagram allows the technician to eliminate possible problems with the circuit by finding what is missing. Finding the right diagram minimizes the time it takes to diagnosis the failure in the circuit. © Jones & Bartlett Learning

PFI Injector Diagnosis and Service 3-3 Examine PFI service procedures.

Fuel injectors are precision components that are specifically calibrated to each engine. Fuel injectors can fail over time as follows: Clog partially or fully Stick open or closed Fail open or shorted Experience O-ring failure Fuel injectors are designed to spray atomized fuel into the air intake charge just behind the intake valve as it opens. Injectors are selected for their spray pattern and flow rate. These correspond to the air intake design and engine displacement, along with other factors on engines that feature turbo- or supercharging, which can increase the quantity of air entering the combustion chamber. Fuel injectors should spray a fine mist of fuel (FIGURE 3-7). Fuel injector faults due to partial or full clogging, stuck open or closed, inductor failing open or shorted, or an O-ring failure cause drivability concerns and can set misfire and/or fuel trim DTCs.

FIGURE 3-7 Fuel injectors must function properly to deliver atomized fuel droplets into the air intake for proper combustion in each cylinder.

© Jones & Bartlett Learning.

A partially clogged fuel injector will have an abnormal spray pattern, and a clogged injector will have little or no fuel from the discharge orifice (FIGURE 3-8). Clogged fuel injectors that otherwise test normal can be cleaned and put back into service.

FIGURE 3-8 Partially clogged fuel injectors show abnormal spray patterns. Abnormal spray patterns can cause engine performance issues. © Jones & Bartlett Learning.

Fuel injectors can be cleaned on the car using an injector cleaning service tool (FIGURE 3-9). Most tools contain a tank for the cleaning solution, a pressure gauge, and a hose with adapters to connect to the injector fuel rail. The fuel pump on the vehicle is disabled by removing a fuse or relay, and the fuel line from the tank is disconnected so the cleaning solution does not go back toward the fuel tank. The fuel injector cleaning tank hose is connected to the fuel rail and is pressurized to the correct fuel pressure normally present in the fuel system. The engine is then started and runs until the cleaning solution is used up. This process should clean any gum and deposits from inside the fuel rail and injectors.

FIGURE 3-9 On-vehicle fuel injector cleaning is done with a cleaning solution pumped into the fuel rail while the engine is running. OTC, company owned by Bosch.

If injectors are very clogged, stuck open, or closed, or the on-car service did not fully restore injector performance, the injectors can be removed and cleaned using a workbench injector cleaning station (FIGURE 3-10). The injectors are cleaned first in a small ultrasonic tank and then installed onto the cleaning station. The station has a built-in pulsed voltage source to open and close the injectors as the cleaning solution circulates through. The spray patterns are visible so you can determine when the injectors have returned to normal flow and spray pattern. Injectors that do not perform as required after cleaning must be replaced.

FIGURE 3-10 An ultrasonic fuel injector cleaner can be used for off-vehicle injector cleaning. © Jones & Bartlett Learning.

The inductive coil in the injector can fail open or shorted. A normal injector digital storage oscilloscope (DSO) pattern is shown in FIGURE 3-11. Connect the DSO signal lead to the PCM control side (usually ground side) that connects between the injector and the PCM. This is usually done at the injector if it can be reached. Some intake manifold designs make this impractical for some or all of the injectors, so you will have to access the injector ground wire at the PCM. Connect the DSO ground lead to a known good ground. Set the voltage scale to 10 V/division and the time to 1 ms/division. Start the engine and you should see a pattern similar to the one in FIGURE 3-12. Always refer to the service information for your vehicle, however, as some injector patterns can differ. The injector on-time is shown by the portion of the waveform at 0 V. This injector is on for almost 2 ms. The off-time is the portion that is at source voltage. When the injector is turned off, as with all inductive devices, a magnetic field–induced voltage spike occurs. This is what you see as the PCM opens the ground path turning the injector off.

FIGURE 3-11 Fuel injectors are checked for inductive faults using a digital storage oscilloscope. Courtesy of Pico Technology Ltd.

Description

FIGURE 3-12 Using the oscilloscope to compare different injector waveforms will allow the technician to see any anomalies. © Jones & Bartlett Learning.

Description Injectors that fail open will either be at a constant source voltage, with no on-time signal, or they may operate normally until they reach engine operating temperature and slowly fail open. You can look for either of these by watching the DSO pattern while the engine runs. An injector that fails shorted can cause damage to the PCM. The decrease in resistance of the injector coil increases circuit current, which can cause the injector driver inside the PCM to fail open. Once this happens, the PCM has to be replaced, as does the failed injector. The DSO pattern for a failed PCM injector driver is a steady source voltage line on the injector ground side. You can measure injector resistance to verify the condition. Measure resistance across the injector pins with the engine off and with the injector harness connector removed from the injector. Compare your readings to specifications, and remember that most specifications are for the engine at ambient (not running) temperature. A reading very close to 0 Ω indicates a fully shorted injector coil. Readings that are lower than specification indicate an injector coil that is failing toward a short condition. A reading that is open loop (OL) or above resistance specifications indicates an open circuit failure, and the injector should be replaced. Injector O-rings are used to seal the injector to the fuel rail and the intake manifold. The fuel rail is fastened to the manifold and supports the injectors to keep them seated. O-ring failures at the fuel rail will cause fuel leaks. These not only cause drivability concerns but can also lead to engine fires. These failures must be corrected before returning the vehicle to the customer. (If they refuse the service, be sure to note this as a fire hazard on your repair order and notify the service advisor to get a signature of acknowledgement from the customer.) O-ring failures on the intake side allow unmetered air to enter the engine. This can cause system too lean DTCs (P0171) and drivability concerns, such as a rough idle or hesitation.

O-rings are not difficult to replace. Obtain the correct parts and use a very light coating of engine oil on the O-ring to seat it onto the injector and then into the fuel rail and intake manifold. Follow service procedures as outlined in the service information and torque the fuel fasteners to specification (FIGURE 3-13).

FIGURE 3-13 Fuel injector O-rings are serviced by removing the fuel rail and the affected injector(s). © Jones & Bartlett Learning.

Replacing a failed injector requires that you obtain the correct part. Many technicians prefer to replace all injectors rather than just one on a high-mileage vehicle. This makes sense in that the fuel rail is removed, and it may cost the customer a repeat of labor charges if another injector fails soon after. Warranty repairs usually require replacement of only the failed injector. TECHNICIAN TIP Installation of an incorrect injector, or a full set of incorrect injectors, can cause engine performance issues, including no or unstable idle, lack of power, too lean or too rich, and more. It is critical that the correct injector(s) be installed. Many injectors are color coded and have unique harness connector designs to help ensure the correct part is used as a replacement.

To test fuel injectors and their related components, follow the steps in SKILL DRILL 3-2.

SKILL DRILL 3-2 Testing Fuel Injectors and Their Related Circuit Components

Description 1. Obtain the service information for inspecting the fuel injector on the vehicle.

Description 2. Perform a visual inspection of the fuel injectors and fuel rail. Note any loose connectors or fuel leaks. Review any leak issues with your instructor before continuing. Do not perform any testing if fuel is leaking anywhere in the fuel system.

3. Measure one of the injectors for resistance following the service information procedure, noting the temperature of the injector, and compare to specifications. Note that the resistance reading will increase as temperature increases. That is why the specification has a temperature range associated with it.

4. Carefully install the noid light into the injector connector you disconnected for the resistance test. Start the engine. The noid light should blink to indicate the PCM is turning the circuit ON and OFF.

Description Description 5. Remove the noid light and return it to its storage location. Install the injector harness connector onto the injector. Obtain a digital storage oscilloscope. Set it up according to the service information to view the injector waveform. Generally, connect the signal lead to the injector ground using a suitable back probe tool. Connect the ground lead to the battery negative or a known good ground. General scope scale settings require the time be between 2 and 5 ms/division and the voltage 5 V/division. Review the pattern with your instructor. Note the injector on-time portion and the inductive kickback when the injector is turned OFF.

6. Return all test equipment to its storage location. Create a repair order that summarizes your test results, resistance, noid light, and DSO tests. 1-4, 6: © Jones & Bartlett Learning; 5: Courtesy of Pico Technology Ltd.

PFI Fuel Pump Service Procedures 3-4 Employ PFI fuel pump testing procedures.

The fuel pump module integrates the fuel pump, fuel filter, pressure regulator, and fuel tank level sensor. Most on-board diagnostics generation II (OBD II) vehicles use a returnless fuel system, where there is no fuel return line from the fuel rail on the engine and back to the tank (FIGURE 3-14). This helps reduce fuel tank temperature, as the return type allows the returning fuel to pick up engine heat and heats up the fuel in the tank. This can increase evaporative (EVAP) hydrocarbon emission levels requiring more system purging and a larger EVAP storage tank.

FIGURE 3-14 Fuel pressure testing uses a fuel pressure gauge connected to the fuel delivery line or fuel rail test port. © Jones & Bartlett Learning.

Some PFI systems control fuel pressure by operating the pump at different voltage levels. This may be as simple as using a resistor in series with the pump. There are two current paths for the fuel pump voltage. One path uses the resistor in series with the fuel pump to reduce voltage at the pump, reducing output pressure under idle or very light load conditions. The PCM switches to the source voltage path for

all other conditions. The other method uses a duty cycled output voltage to control the fuel pump motor speed and resulting pressure. Heavy load conditions require the fuel pump to operate at full speed, 100% duty cycle. Idle and light load conditions use a duty cycle of less than 100% to reduce pump speed and resulting fuel pressure. This type of control may use a fuel pump control module located near the fuel tank. Verify the fuel pump operating system before you begin any testing by reviewing related service information.

Fuel Pump Testing Fuel pump testing centers around one of two scenarios: a crank no-start or fuel pressure–related faults. A crank no-start condition may be caused by a faulty fuel pump or a voltage issue. Most fuel pumps prime when the ignition key is turned on or, on most vehicles with push button start, when the driver’s door is opened. Listen for the fuel pump turning on for about 2 seconds to prime the fuel line. If you hear it, that at least lets you know the fuel pump is turning ON. If you cannot hear it, most scan tools allow for key-on-engine-off (KOEO) testing of the fuel pump. Use the scan tool to activate the fuel pump. If the fuel pump does not turn ON, follow the service information diagnostic procedures to test the fuel pump circuit. If a fuel pump does turn ON but there is a DTC or engine performance issue that could be related to the fuel pump, with respect to fuel pressure and volume, it is usually first tested with a fuel pressure gauge. First, disable the fuel pump and let the engine run until it stalls. This relieves fuel pressure in the line so you can safely connect the fuel pressure gauge. Connect the gauge to the engine fuel rail test port or follow service procedures if an in-line fuel adapter is required. Restore the fuel pump operation. You can test fuel pressure using the scan tool with the active test while the engine is OFF. This is a good idea to verify there are no fuel leaks before starting the engine. It is also a good idea to have a working fire extinguisher nearby when working on the fuel system. Operate the engine and verify fuel pressure is within service information specifications. The most common fault is low fuel pressure. This can be caused by a clogged fuel filter, a damaged fuel line, a pressure leak in the fuel system, or a worn fuel pump motor. Visually check the fuel lines for damage or leaking. Internal leakage could be occurring due to a faulty pressure regulator in the tank. Some technicians may say a leaky fuel injector could cause low fuel pressure, but that is unlikely. A leaking fuel injector that is large enough to cause low fuel pressure would quickly fill the combustion chamber with fuel and hydrolock the engine. TECHNICIAN TIP A leaky fuel injector is noted by monitoring fuel pressure after engine shutoff. The fuel pressure should fall only about 1 psi/minute after engine shutoff. If it falls quicker than this, there could be a leaky injector or a faulty fuel check valve/check ball in the fuel pump module.

TECHNICIAN TIP Follow service procedures for removing and installing the fuel pump. Be sure to use special tools for the fuel pump lock ring if required. It is common for a technician to use the wrong tool to seat the lock ring, which leads to a pinched tank seal at the lock ring. Then, when the customer fills the tank, fuel leaks out. This is a very bad situation all the way around, being a safety hazard, a fuel spill, and a very messy comeback situation.

You can check the fuel pump motor for wear by measuring current with an inductive pickup and the DSO (FIGURE 3-15). Set the DSO up to 10 ms/division and 1 V/division. Connect the inductive pickup

around the fuel pump source voltage wire. Start the engine and note the DSO pattern. Most fuel pump commutators have eight segments. You can count each pulse. Each set of eight pulses represents one pump commutator rotation. Using the time scale, you can calculate pump rpm. Look at the waveform for signs of wear. The current should display in even, replicating pulses. A worn commutator will exhibit arcing as it moves across the motor brushes, causing a pattern of uneven pulses. The pattern will most likely repeat, showing that one or more commutator segments are abnormally worn. Replace the fuel pump module to correct this condition (FIGURE 3-16).

FIGURE 3-15 The fuel pump current can be viewed using the DSO and an inductive current clamp.

FIGURE 3-16 The intake fuel pump module contains the fuel pump, filter, pressure regulator, and fuel level sending unit. © Jones & Bartlett Learning.

Fuel pumps may have normal fuel pressure but low volume. This may be due to a worn fuel pump, a clogged filter, or damaged fuel lines. This problem is not that common and in most cases is isolated to a worn fuel pump. Replace the fuel pump module only if fuel pressure or volume is out of specification and you have performed the related component inspections. High fuel pressure situations are rare and are usually due to a faulty fuel pressure regulator or the wrong fuel pump being installed on the vehicle. To perform fuel pump pressure and volume testing, follow the steps in SKILL DRILL 3-3. SKILL DRILL 3-3 Fuel Pressure and Volume Testing

1. When conducting a fuel pressure test, look up the specifications for the vehicle being tested.

2. After the specification has been found, find a tap point to attach a fuel gauge to the fuel system. Most systems have a Schrader valve that allows a fuel gauge to be attached quickly and easily. Note: Do not try to attach a fuel gauge to the high-pressure side of a gasoline direct-injection (GDI) engine. The pressures can exceed 5000 psi (345 bar), which can cause injuries and tool failure.

Description 3. Remove the Schrader valve cap, and attach the fuel gauge to the service port, being careful to clean up any spilled fuel so that a fire will not result.

4. Once the gauge has been hooked up properly, cycle the ignition key to the run position. When this happens, the fuel pump will run for approximately two seconds to prime the circuit. Look for any leaks and visually monitor the reading on the gauge. Document the reading and compare it to the vehicle specifications.

5. Start the vehicle and let it idle. Take another reading and compare it to the service information to determine whether the fuel pump is putting out enough pressure. Shut down the vehicle.

6. After comparing the readings captured from the vehicle, disconnect the fuel gauge from the vehicle and reinstall the Schrader valve cap. © Jones & Bartlett Learning

Switch Input Testing Procedures 3-5 Inspect switched inputs.

A switch input may be used to detect brake operation, for example. This can affect how the PCM delivers fuel as the vehicle slows down. A switch input may at first seem like a mystery in its operation as an input for the engine control unit (ECU) (FIGURE 3-17). It is actually very basic and is the simplest of digital signal inputs to an ECU. Remember that every input is a circuit, and every circuit requires a source, load, and ground. A switch input circuit may use source voltage or a regulated voltage that is less than source voltage.

FIGURE 3-17 A temperature switch moves from an open to a closed or a closed to an open position based on outside input. © Jones & Bartlett Learning.

The load in the circuit is usually a resistor, often called a dropping resistor, since the voltage drops to almost 0 V after the resistor when the switch contacts close, turning the circuit ON. The voltage does not drop when the input switch is in the open contact position, since current is not flowing through the resistor. This circuit creates either a full voltage or no voltage signal as the switch is turned off and on. Because this is a digital signal, the processor can use it without any conversion. The ECU circuit uses a logic gate to monitor the voltage after the resistor. Voltage present indicates the switch is open. Closing the switch turns the circuit on, and the voltage drops to 0 V after the resistor. The ECU monitors this voltage. For example, the brake switch input usually will show “OFF” when the brake is not in use and it will change to “ON” when the brake pedal is pushed to apply the brakes.

Temperature Sensor Testing Procedures 3-6 Inspect temperature sensors.

The PCM requires accurate temperature readings to deliver the correct amount of fuel to each cylinder. Temperature affects the rate of fuel evaporation. A cold start condition requires longer injector on-time so more fuel is delivered to each cylinder to compensate for the slower fuel evaporation rate (change from a liquid to a vapor). Temperature sensor data comes from the use of a thermistor (FIGURE 3-18). A thermistor is a temperature-sensitive resistor. The resistance of the thermistor changes as the temperature changes. Most automotive thermistors have very high resistance when the temperature is cold and low resistance as the temperature increases. These thermistors are labeled NTC for negative temperature coefficient. This means that, unlike most electrical systems and electronic components where resistance increases as temperature increases, the resistance decreases as temperature increases in an NTC-type thermistor.

FIGURE 3-18 Thermistors are used in various places where a particular temperature is needed to help with engine fuel mixture control or for input for ambient air temperature. © Jones & Bartlett Learning.

The thermistor circuit uses a reference voltage and a dropping resistor, similar to the switch input circuit (FIGURE 3-19). The circuit has two loads that share the reference voltage. This is often called a voltage dividing circuit. The PCM monitors the voltage drop between the resistor in the PCM and the thermistor. When the temperature is cold, the thermistor has very high resistance, so most of the voltage

drops across it and the PCM senses approximately 0.5 V. The thermistor has very low resistance at high temperature conditions, about 100 to 200 Ω, and the PCM senses about 4.5 V between the fixed resistor and the thermistor. The thermistor input is an analog signal because the voltage varies as the temperature changes. The PCM processor uses look-up table data that equates the sensed voltage to a temperature. The temperature data are then used by another portion of the processor to determine what action may be required to adjust the fuel system for optimum operation, especially during cold ambient temperature engine start. Follow the steps in SKILL DRILL 3-4 for temperature sensor inspection and testing.

FIGURE 3-19 Temperature inputs are critical to accurate fuel delivery. Most temperature sensors use 5 V shared between a resistor inside the PCM and the thermistor inside the temperature sensor. © Jones & Bartlett Learning.

Description SKILL DRILL 3-4 Temperature Sensor Testing 1. Obtain the ambient temperature diagram and service information for the vehicle.

2. Trace the current path for the temperature sensor using one color (orange) for the signal wire and another color (green) for ground. There are two loads in the circuit: the resistor inside the PCM and the thermistor (temperature sensitive resistor). These may be colored blue.

3. The following tests are based on the most common temperature sensor DTC diagnostic tests:

Description a. Measure voltage on the sensor ground with the harness connected to the sensor. There should be 50 mV or less on the circuit ground. Readings of 100 mV or higher indicate circuit ground resistance, which affects accuracy of the temperature interpreted by the PCM.

b. Disconnect the temperature sensor harness connector. Test for the 5-V (or applicable) reference voltage on the sensor signal wire. A reading of 5 V is normal, and a reading of 0 V indicates there is an open on this wire between the sensor and the PCM. With the harness disconnected, view the scan tool data list. The temperature sensor you are testing should have a value at the default coldest reading. If it does not, the PCM may be using a fail-safe value or there may be a fault in the PCM.

c. With the harness still disconnected from the temperature sensor, use a jumper lead between pins 1 and 2 of the connector. The scan tool data list should now show the default maximum temperature reading. If it still shows the coldest reading, there is an open on one or both of the sensor circuit wires or there may be a PCM fault. If the reading is lower than the default hottest reading, there is resistance in the circuit. Perform a voltage drop test on the signal wire and ground wire. There should be less than a 50-mV drop between the wire at the sensor and the same wire at the PCM.

d. If all harness-related voltage tests are okay, check the resistance of the sensor. Most service information includes a resistance chart or table for this test. Replace the sensor if the values are out of range or the sensor thermistor is open (OL) or shorted (0 Ω). © Jones & Bartlett Learning

Position Sensor Testing Procedures 3-7 Inspect position sensors.

Position sensors provide input data to the ECU about the position of a component (FIGURE 3-20). Throttle and accelerator pedal position sensors provide critical input data to the PCM for fuel control. The sensors may be analog or digital.

FIGURE 3-20 Some position sensors use digital circuits, using modified Hall-effect technology to create an output signal. The output is usually still an analog voltage signal. © Jones & Bartlett Learning.

Description The analog position sensor is most often a three-wire sensor (FIGURE 3-21). The sensor shown uses a 5-V reference that drops across a fixed resistance inside the sensor. This fixed resistor has a conducting contact surface so that a movable wiper in contact with the resistor picks up the voltage. Measuring available voltage at VCP1 and VCP2 of our sample circuit should show the reference voltage value on the digital multimeter (DMM). The ground, identified at EP1 and EP2 on this sample, should be less than 50 mV. The movable wiper picks up the voltage based on where it contacts the fixed resistor. Most electronic throttle systems use two sensors for very accurate position calculations of the throttle and accelerator pedal. The sample shown has voltages that increase at different values, which the PCM uses to detect very small throttle or pedal movements. This example will have a closed throttle signal voltage of 0.8 V on VPA1 and 1.6 V on VPA1. Sometimes the service information and scan tool display a percentage that equates to the position of the component, with 0% being the closed position and 100% being the full open position. Some analog sensors use a signal voltage on one sensor that increases from approximately 0.5 V to 4.5 V while the other sensor decreases from 4.5 V to 0.5 V as the throttle opens or the accelerator pedal is depressed.

FIGURE 3-21 Some position sensors are analog, which require an input and ground, and produce a signal based on position. © Jones & Bartlett Learning.

Description Most newer position sensors use modified Hall-effect circuits to create an analog output signal. These sensors use a magnet attached to the pedal or throttle. When the pedal or throttle move the magnet, it distorts a magnetic field, which alters the circuit output voltage. The advantage of this sensor over the wiper type is that there is no contact between the components so there is reduced chance of faults as the mileage of the vehicle increases due to surface wear on the wiper sensor contacts. To inspect and test position sensors, follow the steps in SKILL DRILL 3-5. SKILL DRILL 3-5 Position Sensor Testing

Description 1. Obtain a wiring diagram for your assigned vehicle. Trace the current path for the throttle position sensor circuit. Refer to the service information to determine the expected voltages at the reference pin, ground pin, and position input pin of the sensor.

2. Verify sensor voltage is present, usually a 5-V reference voltage for analog sensors and some digital sensors. Other digital (modified Hall-effect type) may use source voltage as a reference voltage.

3. The sensor ground should have less than 50 mV at the sensor. Readings of 100 mV or higher indicate resistance on the ground circuit wiring and may result in data look-up table errors. This can result in incorrect throttle operation and drivability issues, including hesitation, surging, and incorrect idle speed.

4. Verify output values with the related service information for the two output signals. Use a DMM to verify voltage and the scan tool to verify the sensor data are within range.

5. Slowly operate the position sensor and record the data using a graphing multimeter or DSO. This tests for any voltage dropouts that can cause intermittent faults or throttle system limp mode operation. A worn throttle actuator and related sensors are often indicated by the vehicle entering limp or fail-safe mode. Upon engine shutoff and restart, the vehicle operates normally until the PCM detects the out-of-range reading again. © Jones & Bartlett Learning

Pressure Sensor and Mass Airflow Sensors 3-8 Inspect pressure and mass airflow sensors.

The manifold absolute pressure sensor provides an input voltage to the PCM (FIGURE 3-22). The MAP and engine speed data are used to calculate engine load. Engine load data are critical to the amount of injector on-time for correct fuel delivery amounts. Engine control systems that use only a MAP sensor (or sensors) are referred to as speed-density fuel control systems and were the most common until the early 1990s when mass airflow sensors took their place. The MAF sensor offers accurate air intake volume measurement into the engine. The early electronic sensors were somewhat problematic; however, improvements quickly came about with the hot wire type becoming the most common on almost every vehicle. The use of MAP sensors almost disappeared until direct injection systems, such as Ford’s EcoBoost paired turbocharging and other similar systems, returned to using one or more MAP sensors and no MAF at all.

FIGURE 3-22 The manifold absolute pressure sensor is used to determine the amount of air entering the engine. © Jones & Bartlett Learning.

Both MAP and MAF sensors provide an analog voltage signal to the PCM. MAP sensors create a signal using a reference voltage (usually 5 V) that drops across a silicon membrane inside the sensor. The membrane is in a sealed chamber that connects to the intake manifold by a small piece of flexible hose or may mount directly onto the intake manifold using an O-ring to provide a seal (FIGURE 3-23). The silicone membrane distorts based on manifold pressure, which changes its resistance, and related voltage drop across it. At idle speed, the throttle is almost closed so the intake pressure is very low (often referred to as vacuum), around 18 to 22 inches of mercury (in-Hg). This creates a large distortion on the diaphragm, and most of the reference voltage drops across it. At idle, the MAP signal is often around 0.5 to 0.7 V. Conversely, at wide-open throttle there is almost zero vacuum in the intake manifold and very little to no distortion of the diaphragm, and the signal voltage is close to 4.5 V.

FIGURE 3-23 MAP sensors use a silicon diaphragm that distorts based on manifold pressure. © Jones & Bartlett Learning.

Description

Case Study: Lack of MAF Signal The DTC diagnostics begin with the OBD II code and its definition along with a description of the related component, if applicable (FIGURE 3-24). The example shows DTCs for an open or shorted MAF signal wire (circuit voltage low = shorted, high = open), an overview of the sensor and how it operates, and a diagram of the MAF sensor hot wire circuit and location on the sensor housing. Note that this MAF also incorporates the intake air temperature sensor, making this a five-wire sensor: three wires for the MAF circuit and two wires for the IAT circuit (FIGURE 3-25).

FIGURE 3-24 The DTC diagnostics contain a description of the component and its function. © Snap-on Incorporated.

Description

FIGURE 3-25 Some manufacturers use a MAF that also has an IAT sensor. If either the MAF or the IAT fails, the whole unit must be replaced. © Jones & Bartlett Learning.

What happens if the PCM has an open or shorted MAF signal wire? First, a DTC will store when the fault occurs and the check engine (malfunction indicator lamp [MIL]) will illuminate. For most vehicles, an open or shorted MAF signal results in a loss of signal (which is normally a varying voltage that increases as intake airflow increases) (FIGURE 3-26). Without a MAF signal, the PCM operates the fuel injector ontime based on throttle position and engine speed. The customer may notice the following symptoms:

FIGURE 3-26 When looking at the signal produced by a MAF, using an oscilloscope to verify the output of the senor may help in quickly diagnosing a bad MAF sensor. © Jones & Bartlett Learning.

Increased engine crank time to start Stalls after initial start Rough or higher than normal idle speed Reduced fuel mileage Reduced power output Follow the DTC test procedures to isolate the cause of the fault. A short to ground is indicated when the MAF signal wire has continuity to ground. An open is indicated when there is infinite resistance (OL) between the MAF and the PCM. DTC diagnostics continue with a description of the conditions that store the related code. For this example, MAF sensor signal voltage that is less than 0.2 V for 3 seconds store DTC P0102. This DTC uses 1 trip or 2 trip detection logic based on the engine speed (rpm) when the fault is detected. A list of what could cause the fault shows that there may be an open or short circuit or a faulty sensor, relay, or PCM. The MAF sensor monitor description and strategy are described. The MAF circuit is part of the component monitor covered in Chapter 7 and is monitored continuously when the ignition is ON. The DTC enabling conditions are listed. The DTC example in FIGURE 3-27 does not have any enabling conditions. What this means is that even if another DTC has stored, the MAF circuit is still monitored and can store a DTC if a fault is detected. The malfunction thresholds list what the MAF signal voltage value must exceed to store the related DTC. The MAF normal operating range voltage is included for reference.

FIGURE 3-27 The DTC diagnostics include how the DTC is detected, the monitor description, and the strategy. © Snap-on Incorporated.

OBD II DTCs usually have an associated drive cycle (FIGURE 3-28). It is important to note that while it may be called a drive cycle, driving pattern, or similar terminology, driving may not be part of the drive cycle. For this MAF DTC, the driving pattern is actually monitoring the MAF sensor data on the scan tool while running the engine and verifying whether the DTC is present. This is done at engine idle speed and at an engine speed that is 4000 rpm or higher, each at 5 seconds. For this example, the manufacturer’s scan tool allows you to see the monitor judgment results. This may or may not be possible with an aftermarket scan tool.

FIGURE 3-28 The drive cycle is included with the DTC diagnostics. © Snap-on Incorporated.

The actual hands-on diagnostics for a DTC begin with step 1 of the inspection procedure (FIGURE 329). Complete the first step and note the result (FIGURE 3-30). The result then directs you where to go next. In this example, if you have DTC P0102, this indicates low voltage due to an open circuit. Begin diagnosis at step 2, which is a verification using the digital multimeter that source voltage is present at the MAF so its internal circuit can operate (FIGURE 3-31).

FIGURE 3-29 The DTC diagnostics list the inspection procedures step by step. Some may include a circuit diagram for reference. © Snap-on Incorporated.

FIGURE 3-30 When diagnosing a check engine light, use a scan tool to scan the vehicle for service codes and then work through the flowchart to diagnose the issue. © Jones & Bartlett Learning.

FIGURE 3-31 The second step in this flow chart for the P0102 is to check power to the MAF sensor. Using a voltmeter, verify that the connector has power and ground on the appropriate terminals. © Jones & Bartlett Learning.

If DTC P0103 is present, you begin at step 5. This step has the technician testing for continuity between the MAF ground wire and chassis ground. Follow each step to isolate the cause of the fault, which may be an open or short in the wiring harness, a faulty MAF sensor, a faulty relay, or the PCM. Your accuracy depends on following each step and doing each action correctly. Testing at the wrong pin of a connector will yield an incorrect reading on the DMM and lead you to an error in judgment of what is at fault. As the technician, you are under pressure to move quickly. You must balance this by knowing that performing each step and verifying the results ensures your diagnosis is spot on and that when you make the repair the issue is actually fixed and will not come back. The most common MAF sensor uses a hot wire located in part of the intake airflow between the air filter and the throttle body (FIGURE 3-32). The hot wire is part of a bridge circuit. The bridge circuit has four loads: the hot wire, a thermistor that allows for accuracy even when the ambient temperature changes (think cold of winter to high heat of summer), and two fixed value resistors. The bridge circuit uses battery source voltage and is regulated to keep the hot wire at around 290oF. Incoming ambient air removes heat from the hot wire, and the circuit must increase current to keep it at 290oF. As intake air amounts increase, current to keep the hot wire at the correct temperature increases, as does the output voltage signal from the MAF to the PCM. MAF sensors provide very accurate intake air volume data because the sensors take a direct measurement of air volume no matter the temperature or barometric pressure, which affects air density. For MAF sensor inspection and testing, follow the steps in SKILL DRILL 3-6.

FIGURE 3-32 The MAF uses a heated wire to determine the amount of air entering the engine. A bridge circuit is used to provide an analog output voltage to the PCM. © Jones & Bartlett Learning.

Description SKILL DRILL 3-6 MAF Sensor Inspection

1. Verify source voltage is present and the sensor ground has less than 50-mV drop between the sensor and the related ground.

2. Compare output voltage in the related engine rpm chart in the service information. (Not all manufacturers offer this information, so you may have to compare to a known good vehicle.)

3. MAF sensor hot wires can become contaminated by the following: a. Debris from an air filter that someone attempted to clean using compressed air. This causes the filter fibers to loosen up and then melt onto the hot wire as incoming air carries these loose fibers through the intake. b. Use of aftermarket air filters that do not meet OE design specifications or quality. c. Use of aftermarket air filters that can be cleaned and reused. These filters are designed to work with the MAF if the filter coating is applied correctly. Many users overapply the solution, allowing the solution to contaminate the hot wire. d. Remove the MAF if you suspect hot wire contamination. A visual inspection will determine whether there is a buildup of foreign material. Only use MAF sensor cleaner to remove this material. Use of other cleaners, such as carburetor cleaner or brake cleaner, can dissolve the protective coating on the hot wire. Other cleaners may also leach into the MAF housing and damage the internal electronics. 4. MAF sensor internal circuitry can fail, although this is much rarer than the early MAF sensors used in the 1980s and early 1990s. The sensor may need to be replaced if the wiring, related test voltages, and hot wire visual inspection are all normal.

© Jones & Bartlett Learning

TECHNICIAN TIP A small number of vehicles use a Karman Vortex MAF (FIGURE 3-33). This MAF does not use a hot wire bridge circuit. Some of the air entering the sensor passes over a vortex generator, which causes the airflow to tumble. This creates pressure pulses that are detected using an LED and photo diode. These pressure pulses are used to create a digital (square wave) output signal to the PCM.

FIGURE 3-33 A small number of vehicles use Karman Vortex MAF sensor. This sensor does not use a hot wire circuit. It measures airflow tumble through a vortex generator and outputs a digital signal. © Jones & Bartlett Learning.

Description

Sensor circuits may provide inaccurate data due to excessive resistance in the circuit. There should be less than a 50-mV drop through the sensor wiring and the sensor ground. Remember that voltage drops when current is present in a circuit and that voltage can drop across a wire or connector with excessive resistance. Always check circuit voltage drop through the wiring, connectors, and ground before replacing what seems like a bad sensor; it could be a circuit resistance fault, and installing a new sensor will not correct the condition.

WRAP-UP Ready for Review The port fuel injection system delivers fuel to the engine by opening an injector and spraying fuel behind the intake valve. PFI components include the fuel pump, fuel delivery components, fuel injectors, and the PCM. Service information provides support for the strategic diagnostic process for PFI system inspection and testing. DTC service information includes problem symptom tables; DTC diagnostics; and component inspection, removal, and installation procedures. PFI diagnostic tools include the scan tool, the DMM, and the DSO. PFI diagnostics usually require use of the system wiring diagram to complement the service information. Electrical wiring diagrams provide information on wire color, circuit paths, source and ground location, connector and connector pin numbers, and electrical component locations. Fuel injector testing includes viewing DSO injector waveforms and measuring resistance of the injector. Fuel injectors can fail open or shorted. A shorted injector may cause the related injector driver in the PCM to fail, requiring both to be replaced. Fuel injectors are selected for an engine based on flow rate and spray pattern. Replacement injectors must match the original, or a variety of engine performance concerns can result from use of the wrong injector(s). Fuel injector O-rings seal fuel pressure on the fuel rail side and seal off outside air from entering the engine on the intake manifold side. The fuel pump can usually be activated using the scan tool to verify that it turns ON. A fuel pressure gauge is often used on PFI systems to verify system fuel pressure. The fuel pressure gauge may connect onto a fuel rail mounted test port or may require an adapter to mount onto the fuel line. Low fuel pressure may be caused by a worn fuel pump or fault fuel pressure regulator. Fuel pump motor current can be viewed using an inductive pickup on the motor circuit and the DSO. High fuel pressure is the result of the wrong fuel pump or a faulty fuel pressure regulator. Fuel pump installation procedures must be followed, and any special tools to tighten the fuel tank lock ring should be used to prevent a fuel leak and fuel spill.

Key Terms Fuel map The program that is run by the PCM that relates engine load to rpm. It provides the fuel injector with the correct amount of on-time to increase engine performance. Fuel pump module This consists of a fuel pump, fuel level sensor, fuel tank pressure sensor, and hanger. Long-term fuel trim (LTFT) A calculation used to direct long-term engine operation. It is calculated by the PCM based on how the engine is operating currently. Position sensor A sensor that monitors the position of a component. The sensor may be analog or digital. Some monitor the movement of a component, such as an HVAC blend air door or the engine throttle blade, as it moves from one position to another. Others monitor the location of rotating components, such as the crankshaft. Short-term fuel trim (STFT) A calculation used to determine the amount of fuel the engine is using. It adjusts based on the upstream oxygen sensor signal.

Review Questions 1. Fuel injectors are statically tested using which of the following? a. Voltage using the DMM b. Voltage using the DSO c. Resistance using the DMM d. Amperage using the DMM 2. Refer to the system diagram shown on the next page. Connect the DSO to view cylinder 4 injector waveform to which of the following? a. Number 4 injector pin 2 and ECM pin 49 ground point b. Number 4 injector pin 1 and ECM pin 50 ground point c. ECM pin 19 and number 4 injector pin 2 d. Number 4 injector pin 1 and ECM pin 49

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3. All of the following statements are correct about inductive type fuel injectors EXCEPT: a. An injector can fail due to internal contamination causing a restriction. b. A leaky injector can cause engine hydro lock. c. Injector resistance decreases with temperature increase. d. A damaged injector O-ring on the intake manifold can cause a lean condition. 4. Which of the following statements is correct? a. Most fuel pumps are located near the fuel tank and mounted to the frame/unibody structure. b. Injectors are controlled by turning on the source voltage. c. Fuel injectors require only one O-ring. d. A shorted injector coil can cause a PCM failure. 5. All of the following fuel pump statements are correct EXCEPT:

a. The fuel pump always operates at 12 to 14 V. b. A two-speed fuel pump may use a resistor in series with the pump for low speed. c. The PCM may control fuel pressure using duty cycling control of the fuel pump. d. Low fuel pressure can cause DTC P0171. 6. The injector ON voltage is which of the following in the waveform on the next page? a. Source voltage b. 180-V spike c. 8.3 V d. 0 V

Description Description © Jones & Bartlett Learning

7. Considering the diagram below, you can test fuel pump current at all of the following EXCEPT: a. Between pin C1–18 and fuel pump pin 1 b. Between pin C3–47 and fuel pump pin 1 c. Between fuel pump pin 2 and ground G301 d. Between C406 and fuel pump pin 1

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8. Refer to the fuel pump current waveform shown below. How many commutator segments does this pump have? a. Four b. Six c. Eight d. Twelve

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9. Refer to the fuel pump current waveform shown above. What does this waveform indicate? a. A clogged fuel pump intake strainer b. A leaky injector that is reducing fuel pressure on cylinder 4 c. Faulty fuel pump relay contacts d. A worn fuel pump commutator 10. Input sensor grounds can have up to __________ measured at the sensor ground. a. 0 V b. 0.05 V c. 0.150 V d. 0.5 V

ASE Technician A/Technician B Style Questions 1. Technician A says fuel injectors should be tested for resistance and compared to service specifications when they are at engine operating temperature. Technician B says a fuel injector can pass a resistance test but fail open or shorted after the engine reaches operating temperature. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B 2. Refer to the fuel injector patterns shown below. Technician A says the injector on-time is the portion of the pattern at 0 V. Technician B says the injector has on-time of about 1.8 ms. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B

Description © Jones & Bartlett Learning

3. Refer to the fuel injector patterns shown above. Technician A says the fuel injector pattern in red indicates an open injector coil. Technician B says this injector could cause a cylinder misfire DTC? Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B 4. Technician A says high resistance on the temperature sensor ground will result in the PCM interpreting a temperature that is lower than it actually is. Technician B says an open temperature sensor ground circuit will result in a 0-V signal to the PCM. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B 5. A vehicle is in the shop for a crank but no-start condition. Technician A says using throttle body cleaner sprayed into the intake could quickly verify a fuel or ignition fault. Technician B says you can usually hear the fuel pump prime when the door opens or when the key is turned to the ON position. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B 6. Refer to the fuel pump wiring diagram shown below. Technician A says the fuel pump relay is source controlled. Technician B says excessive voltage drop at the battery junction block could affect relay and fuel pump operation. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B

Description © Jones & Bartlett Learning

7. Technician A says using fuel pump current for diagnosis is best done with the DMM. Technician B says the DSO can show a worn fuel pump commutator. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B 8. Refer to the diagram shown below. Technician A says air filter fibers could cause lower than normal voltage at pin 5 of the MAF. Technician B says a damaged air intake hose could cause lower than normal MAF signal voltage. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B

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*** 9. Fuel pressure rapidly drops to 0 after the engine is turned OFF. Technician A says this is normal. Technician B says a leaking injector could be the cause. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B 10. Technician A says low fuel pressure may be due to a fuel excessive resistance in the fuel pump wiring. Technician B says excessive fuel pressure could indicate a faulty fuel pressure regulator. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B

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CHAPTER 4

Direct Injection System Diagnosis LEARNING OBJECTIVES After studying this chapter, you should be able to: 4-1

Explain direct injection system components and their function.

4-2

Diagnose GDI high pressure fuel pump and lift pump concern.

4-3

Describe GDI system maintenance procedures.

4-4

Describe the operation of combination PFI and GDI systems.

YOU ARE THE AUTOMOTIVE TECHNICIAN A 2018 Hyundai Sonata 4 cylinder is in for the check engine light ON and DTC P0171 fuel system lean. Which of the following are applicable and in what order as they apply to the diagnostic process? Verify the customer concern. Check for DTCs. Check battery voltage. Review applicable service information for the DTC. Review data list input and output values. Review the wiring diagram. Look up normal data parameters. Review freeze frame data. Check the Mode 6 monitor data. Check air-fuel ratio sensor operation. Inspect for exhaust leaks ahead of the air-fuel ratio sensor. Check the lift pump fuel pressure. Inspect the MAF/MAP sensor. Inspect the intake valves for deposits. Gasoline direct fuel injection (GDI) is similar to port fuel injection (PFI) from a diagnostic viewpoint. A technician’s knowledge of GDI systems allows him or her to build on PFI knowledge and so apply the strategic diagnostic process.

Gasoline Direct Fuel Injection Component Review 4-1 Explain direct injection system components and their function.

The gasoline direct fuel injection (GDI) system components include the following (FIGURE 4-1):

FIGURE 4-1 The GDI system uses similar components to the PFI system; however, the fuel is injected under very high pressure directly into the combustion chamber. © Jones & Bartlett Learning.

Description Powertrain control module (PCM) Inputs to support fuel control Intake air temperature (IAT) and engine coolant temperature (ECT)

Crankshaft position (CKP) and cam position (CMP) Accelerator position sensor (APS)/throttle position sensor (TPS) Mass airflow (MAF) or manifold absolute pressure (MAP) Air-fuel (AF) ratio sensor Lift fuel pump High-pressure fuel pump High-pressure fuel injectors Port fuel injectors (on some engines) PCM monitor sensor input data uses fuel data mapping to determine injector pulse width (on-time) to deliver the necessary amount of fuel. The PCM usually controls one or more relays or communicates with a fuel pump control module to operate the lift fuel pump. This fuel pump is designed to deliver fuel within a specific pressure range and volume to the high-pressure fuel pump that is usually located on the engine. The high-pressure fuel pump is operated by a dedicated lobe on the camshaft. This cam lobe may have three, four, or five sides and operates the pump plunger to create an outlet pressure from 300 to over 2000 psi (FIGURE 4-2). The PCM operates a pressure control valve to maintain the desired fuel pressure in the fuel rail for the GDI injectors. The fuel injectors for GDI systems spray fuel directly into the combustion chamber. This is why the fuel pressure is so high, as it must be higher than the compression pressure inside the cylinder. GDI injectors may use inductive solenoids to open the injector or piezoelectric technology. The solenoid type is similar to port fuel injector operation; however, the operating voltage of the injector on some systems may be increased. The PCM may incorporate a stepup voltage transformer to increase source voltage to about 65 V. Some GDI systems actually use one of the other injectors as a coil to create a high-voltage spike to operate the desired injector.

FIGURE 4-2 The lift pump in the fuel tank delivers fuel to the high-pressure fuel pump, which is usually located on the engine. © Jones & Bartlett Learning.

Description TECHNICIAN TIP GDI injectors are selected for their flow rate and atomization properties for the engine they are used on. These injectors usually have a calibration number stamped onto the injector body. This number corresponds to engine application and flow rate. Injectors must be replaced with one with the same calibration number. Use of the wrong injector can lead to a rough running engine, lack of power, and other customer concerns.

Most GDI injectors use piezoelectric crystal layers to control fuel flow through the injector. Piezo crystals are layered in ceramic. There are several hundred layers in the injector to form a piezo stack. Voltage applied to the stack causes the stack to expand a few thousandths of a millimeter to open the jet

needle (FIGURE 4-3). Opening the jet needle allows fuel to flow through the nozzle unit and into the cylinder. Piezo crystal stack injectors allow the PCM to operate the injector for very brief periods of time, an average of 0.4 ms. Remember that port injection is in the range of 2 to 4 ms. GDI can deliver fuel in a much shorter time period due to the very high pressures used, from 500 to 3000 psi. The PCM may also perform multiple injector open events during the intake or compression stroke depending on engine power requirements.

FIGURE 4-3 Piezoelectric GDI injectors use current to expand crystals, which then allow fuel to flow from the nozzle directly into the combustion chamber. © Jones & Bartlett Learning.

Description

GDI injectors use a high pressure O-ring seal on the fuel rail side and usually a retaining clip to ensure correct seal alignment is maintained. The nozzle end often uses a Teflon seal to seal the injector to the cylinder head (FIGURE 4-4). This seal must be replaced if the injector is removed from the cylinder head. A special tool is used to install the seal onto the injector nozzle housing.

FIGURE 4-4 The GDI injector often uses a Teflon seal on the nozzle end to seal against the cylinder head. © Jones & Bartlett Learning.

GDI injector spray patterns depend on the operating mode as follows: Homogeneous Homogeneous stoichiometric Homogeneous power Stratified lean/ultralean Stratified cold start Homogeneous mixtures allow a uniform amount of fuel into the cylinder so that the air-fuel ratio is the same everywhere in the cylinder. Idle and light acceleration use a homogeneous fuel charge that attempts to keep the air-fuel mixture near stoichiometric (14.7:1). The fuel charge is sprayed into the cylinder during the air intake stroke so the fuel vapor can disperse evenly throughout the cylinder. Normal and heavy loads require more injector pulse width at a higher pressure. Also, higher loads expel most if not all the exhaust gasses and open the intake valve (and on some engines also increase valve lift) to maximize the air charge during the intake stroke. The longer pulse width and higher fuel pressure create a wide dispersal of fuel into the cylinder. This is the homogeneous power mode, used during heavy load or rapid acceleration of the vehicle.

Light load conditions use a lean or ultralean mixture in the stratified charge mode. The ability of the PCM to control the incoming amount of fresh air during the intake stroke with variable valve time and/or variable valve lift allows the PCM to go into lean and ultralean modes. Keeping the exhaust valve open during the intake stroke draws some exhaust gas back into the cylinder. Exhaust gas has almost no oxygen, so this gas just takes up space. The intake valve opens later than normal, so a full charge of oxygen-rich air is not drawn into the cylinder, and the exhaust gas is also taking up space. This helps keep the cylinder pressures where they need to be for maximum power output with the lower level of oxygen in the cylinder. The PCM operates the injector compression stroke in a lean or ultralean pulse width and at lower fuel pressure. The fuel is directed toward the dish in the piston, which becomes a mini-combustion chamber. This mode mimics the operation of the diesel engine but with a spark plug. The fuel is injected under a very short pulse width and lower pressure, so it swirls in the small dish area to mix with the available oxygen and is ignited by the spark plug (rather than compression like a diesel engine). At steady cruise, engine power needs are reduced, allowing for the stratified charge mode to increase fuel economy and reduce all levels of emissions. Rich mixtures in stratified charge mode may be used at cold engine start (FIGURE 4-5). The rich fuel mixture is concentrated in the small dish and creates a great deal of heat to bring the engine up to operating temperature quickly. You can often hear this mode as it creates an increase in engine combustion noise during cold engine startup. It lasts about 30 to 45 seconds on a moderately cold start (45°–50o F).

FIGURE 4-5 Most GDI engines use a piston with a small dish area for stratified charge combustion compared to a port fuel injected flat top type piston.

Use of a turbocharger on a GDI engine can greatly increase power for high load conditions while maintaining the high fuel economy and low emission levels during other engine operating conditions (FIGURE 4-6). Most GDI engines with turbocharging also alter cam timing to allow exhaust gas scavenging. This allows the turbocharger turbine to heat up and spool up very quickly so it can compress the incoming air charge (FIGURE 4-7). Another important factor is the injected fuel at a slightly richer mixture in a homogeneous mode that disperses throughout the combustion chamber. The fuel absorbs heat and allows for higher combustion pressures without creating pre-ignition issues. Turbo lag, the time it takes to reach the higher horsepower and torque levels, is virtually eliminated. Also, peak torque is reached and held steady from a low rpm level, usually around 1400 to 1500 rpm, and maintains near maximum throughout the rpm range.

FIGURE 4-6 Many GDI engines use small turbochargers and charge air coolers to increase horsepower output. © Jones & Bartlett Learning.

FIGURE 4-7 An air-to-air intercooler is often used on turbocharged GDI engines to cool the compressed air charge before it enters the intake manifold. © Jones & Bartlett Learning.

TECHNICIAN TIP View GDI at work in lean and ultralean mode. On a GDI-equipped vehicle, select current fuel economy in the driver information display (if available). Reset the fuel economy values before driving the vehicle. Have a co-student or co-worker drive the vehicle while you watch the instrument cluster. Have him or her moderately accelerate from a standstill. Accelerate normally and note how fuel economy increases slowly. Reach a steady speed of about 35 mph and hold the throttle steady. You will see fuel economy jump higher after a second or so. The PCM just entered stratified charge lean or ultralean mode.

The intake air is often cooled using a charge air cooler, similar to a radiator, but it cools the highpressure intake air. This allows more air to enter the combustion chamber. More oxygen with more fuel equals more horsepower. The cooler air charge also helps reduce pre-ignition. Many vehicles are using twin scroll turbochargers. These turbos reduce turbo lag time by using two inlet paths to the two sets of turbine vanes. Exhaust from paired cylinders is directed into each turbo port. This increases the exhaust gas velocity and virtually eliminates turbo lag. Vehicle manufacturers are taking advantage of this technology because it allows for large engine horsepower levels with small engine emission and CO2 levels.

High-Pressure Fuel Pump Diagnosis 4-2 Explore GDI high-pressure fuel pump and lift pump diagnosis procedures.

Diagnosis of GDI system–related faults relies on your efficient and thorough use of applicable service information. Most manufacturer and aftermarket service information sites include DTC diagnostics, fuel system component diagnosis, and related component replacement procedures. The GDI lift pump is diagnosed essentially the same way as on a PFI engine. This is a low-pressure pump operating in the range of 30 to 50 psi, and it can be checked for fuel pressure, fuel volume, current draw, and current waveform analysis in the same manner as the PFI fuel pump. The GDI high-pressure pump is a mechanical fuel pump usually operated by the camshaft. A dedicated lobe operates the fuel pump plunger and uses a bucket or roller follower depending on the manufacturer (FIGURE 4-8). Most pumps have a built-in fuel pressure regulator that is controlled by the PCM. The PCM duty cycles the regulator to control the fuel pressure. A fuel pressure sensor is located on the fuel rail, and this input allows the PCM to verify fuel pressure is correct for the related engine conditions. Some engines also use a fuel pressure sensor on the low-pressure side of the fuel system.

FIGURE 4-8 The GDI high-pressure fuel is operated by a dedicated cam lobe and supplies fuel under very high pressure to the fuel injectors. © Jones & Bartlett Learning.

Description TECHNICIAN TIP

The GDI low-pressure lift pump is often controlled by commands from the PCM to the lift pump control module. Testing is similar to a PFI system fuel pump and usually includes use of a fuel pressure gauge, verifying PCM to lift pump module signal, and verifying pump voltage and ground. The digital storage oscilloscope (DSO) current test to check for a worn pump armature may be a valid test depending on pump design. To view GDI high-pressure fuel pump data using the scan tool, follow the steps in SKILL DRILL 4-1. SKILL DRILL 4-1 Viewing GDI High-Pressure Pump Data on the Scan Tool

1. Obtain your assigned vehicle and a scan tool.

2. Access the related service information to determine the nomenclature used on the scan tool to identify parameter ID (PID) data for the GDI fuel pump pressure values, and the related on-vehicle fuel pump inspection procedure.

3.

Follow the inspection procedure. This may include a visual inspection and then verifying the fuel pressure using the scan tool. Note: If the inspection procedure includes obtaining values under engine load using a power braking method, be sure to raise the vehicle off the ground high enough that the tires are not in contact with the shop floor. This is required to prevent the vehicle from moving during the test even though you are applying the brake.

4. Note your readings from the scan tool during the test and compare them to the service specifications. Verify your test results with your instructor.

5. Create a repair order for your GDI high-pressure fuel pump pressure test. 6. Return the scan tool and any other components to their storage location. © Jones & Bartlett Learning

TECHNICIAN TIP GDI high-pressure components usually require using new fasteners when installing the high-pressure fuel pump. Fuel lines and fuel clips may also require replacement. Follow the service procedures exactly as stated. The high pressure in these systems can lead to a very large fuel leak, a vehicle fire, or if fuel is leaking it can lead to a serious injury or death if the fuel under pressure cuts into body tissue.

GDI fuel pump faults include the following: Low oil or wrong oil causing damage to cam follower and camshaft lobe Pressure regulator failure Spring failure Internal mechanical component failure A GDI pump that is making abnormal noises indicates a mechanical failure. Follow the service procedures to inspect the pump unit. Upon removal you can inspect the cam lobe and cam follower for damage. Damage to these components requires replacing the camshaft and cam follower (FIGURE 4-9). It may be prudent to also replace the pump assembly if there are no signs that low oil, incorrect oil, or lack of oil changes caused the condition. A failed pump spring requires pump replacement.

FIGURE 4-9 The high-pressure fuel pump is operated by a lobe on the camshaft. Inspecting it for damage from poor oil quality or metal fatigue should be replaced with a quality component. © Jones & Bartlett Learning.

The pressure regulator can usually be tested using the scan tool active test mode. Monitor the fuel pressure data while selecting fuel pressure command options with the scan tool. No change in pressure will be indicated by no change in fuel rail pressure and no change in fuel trim data. A faulty pressure regulator usually requires replacing the pump assembly; however, refer to the service information to verify the inspection and repair procedures. An internal pump failure can cause erratic fuel pressure, including consistent low or high pressure. There may be an internal leak or a broken component in the pump. Inspect as follows: Diagnose DTCs, if present. Observe fuel pressure sensor data fuel values on the scan tool data list and compare to service information normal range specifications. Erratic fuel pressure readings may indicate a fuel pump or fuel pressure sensor fault. Verify lift pump pressures are normal before condemning the high-pressure fuel pump and related sensor.

GDI System Maintenance 4-3 Describe GDI system maintenance procedures.

GDI injectors operate at higher voltages than PFI injectors. Solenoid-type GDI injectors require 50 to 60 V to operate. Piezoelectric GDI injectors operate at a little over 100 V. This voltage can be achieved by using capacitors to boost the voltage inside the PCM. Some solenoid-type systems use one injector solenoid coil to act as a transformer to boost voltage to another injector so it can function. GDI injectors can fail in a similar manner to PFI injectors. The solenoid can fail open or shorted, and the piezoelectric unit can fail. The injectors can clog due to contaminated fuel. They can stick closed or open. The service procedures offer a diagnostic flow chart to follow to isolate the cause of the concern. These failures may be indicated by random or specific cylinder misfire DTCs. Unlike PFI injectors, diagnosis is primarily centered around the scan tool for isolating the cause to one or more injectors. The only digital multimeter (DMM) test is usually isolated to measuring injector resistance. Due to the higher system voltages and current to operate GDI injectors, do not use the DSO unless the service information directs you to do so. The injector seal to cylinder head can fail, causing combustion pressure leaks. Inspection for this requires removing the injector. There should not be any gaps or shrinkage of the seal on the injector. These seals are not reusable. Removing an injector requires installing a new Teflon seal on the outlet side of the injector. A simple special tool is used to install the seal (FIGURE 4-10). Place the new seal on the special tool. Place the tool on the injector nozzle and slide the seal onto the nozzle and into the groove until it seats fully. Follow the service procedures to install the injector onto the fuel rail. Be sure to use new clips and fasteners if called for. Do not reuse clips and fasteners if new ones are specified. To install GDI injector seals, follow the steps in SKILL DRILL 4-2.

FIGURE 4-10 A special tool that evenly expands the GDI injector Teflon seal is required to install it on the injector. © Jones & Bartlett Learning.

SKILL DRILL 4-2 Installing GDI Injector Seals

1. Obtain an injector with seals installed, a new seal, and the seal installation tool from your instructor.

2. Access the related service procedure for the vehicle or engine type this injector is from. Review the seal removal and installation procedures.

Description 3. Follow the procedure steps to remove the cylinder head to injector seal. Be careful not to damage the injector. If you damage the seal retaining area, the injector will have to be replaced.

4. Install the new seal using the special service tool. Apply the specified seal lubricant and install the seal on the tool. Slide the seal down the stem of the tool and onto the injector.

5. If instructed to do so, also install the seals for the injector to the fuel rail side of the injector.

6. Complete a repair order for injector seal replacement. Clean your work area and return all components and tools to their storage area. © Jones & Bartlett Learning

GDI Fuel System Cleaning GDI offers some great advantages over PFI. Unfortunately, the lack of fuel on the intake valves, like a PFI engine, allows for carbon buildup on the valves. This primarily occurs with intake valves, but exhaust valves can also have buildup issues. The PFI injector sprays fuel behind the intake valve, and this helps keep deposits from building up on the back of the valves. GDI fuel is injected into the cylinder so there is essentially no cleaning action on the valves. PCV blowby gases can cool on the valves, and the buildup of carbon begins (FIGURE 4-11). Some car companies use PFI injectors on their GDI engines to help reduce this problem. This buildup can lead to part throttle hesitation, lack of overall performance, and random or specific cylinder misfires. There are two methods to remove these deposits:

FIGURE 4-11 Carbon buildup on the valves may be an issue with GDI engines. © Jones & Bartlett Learning.

Using a liquid cleaning solution Walnut shell blasting of the valves and valve passages Several companies offer intake system cleaning solutions. These may be effective if the carbon buildup is not extreme. You can use a bore scope to view inside the intake, to determine the level of car buildup and thus to determine whether the cleaning solution may be a service option for the customer. The advantage with the cleaning solution method is that it does not require removal of the intake manifold from the engine. The walnut shell method requires the walnut shell media and a media blaster tool. Remove the air intake to access the intake valves. Follow the media blaster operating instructions to blast away the carbon buildup (FIGURE 4-12). Reinstall the intake following the service information procedures. To clean carboned intake valves using the walnut shell blasting method, follow the steps in SKILL DRILL 43.

FIGURE 4-12 Walnut shell blasting is a common method to remove GDI carbon buildup. © Jones & Bartlett Learning.

SKILL DRILL 4-3 Cleaning Carboned Intake Valves

1. Obtain your assigned vehicle and related service information for the intake manifold removal procedure.

2. Follow the procedure to remove the intake manifold. Follow your instructor’s procedures to organize and label fasteners so that they can be reinstalled correctly during intake manifold installation.

3. Begin with cylinder 1. Good practice is to use cloth towels or painter tape to cover adjacent intake cylinders to prevent contamination or small fasteners from entering the intake path and falling into the cylinder.

4. The intake valves must be closed to prevent walnut shell particles from filling the cylinder. Rotate the crankshaft by hand if required until the intake valves are closed.

5. Obtain the intake cleaning machine and fill the storage cylinder with walnut shell media. Connect the machine to shop air and also have a shop vacuum.

6. Wear eye protection. You should also wear a mask to avoid breathing in any of the media dust. Use the media blaster to clean the carbon buildup on the intake valves and intake runner in the cylinder head. Use the vacuum to gather the media and carbon as you perform the cleaning.

7. Remove all the carbon and then use the vacuum to remove all media and loose carbon material. Cover this cylinder with painter tape or use a cloth/rag to protect this intake runner and move on to the next cylinder. If needed, rotate the crankshaft until both intake valves are closed. Repeat on all cylinders until finished.

8. If all is okay, remove all the tape or cloths protecting the cylinders. Clean any media residue off the gasket sealing surfaces and from inside the intake runners. Reinstall the intake manifold and other related components that were removed. Torque all fasteners and note that the intake manifold usually requires the fasteners to be torqued in a specific order. 9. Complete the repair order for your intake valve cleaning service. Return all equipment and tools to their storage location. © Jones & Bartlett Learning

Operation of Combination PFI and GDI Systems 4-4 Describe the operation of combination PFI and GDI systems.

Ford, Toyota, and other vehicle manufacturers have internal combustion engines (ICE) that have lowpressure PFI and high-pressure GDI systems (FIGURE 4-13). This increases cost, but there are many benefits, including some learned from seeing the carbon buildup on the intake ports and valves of GDI systems over several years. Toyota engines started using this feature earlier than Ford and the few others did, although Ford has more engines overall at the moment with this technology, including turbocharged variants. The early Toyota versions were primarily focused on keeping the intake deposits to a minimum and taking advantage of GDI at steady cruise to increase fuel economy. The current engines offer much more as inventiveness and updated technology are incorporated in the following areas:

FIGURE 4-13 Some manufacturers have ICE with both PFI and GDI systems. © Snap-on Incorporated.

Increased PCM processing speed Updated variable valve timing (VVT) cam phasing systems Improved injector orifice design Reducing injector noise The increase in processing power allows for improved fuel injector control on both the intake port and direct into the cylinder. This requires a much more complex fuel delivery map on the software side of the PCM programming and the ability of the hardware to process the input data much faster. The improvements also affect the output side controlling both the intake and direct fuel injector on-time for

very precise fuel delivery into the combustion chamber. The increased PCM processing speed is also focused on improving VVT control. A more complex VVT control map can be used, along with either oil pressure control or electric motor control of the cam phasing. The intake and exhaust camshafts are advanced or retarded from idle to maximum rpm to take advantage of fuel available at both the intake and inside the cylinder. For example, the recent Toyota DS4 engines use the following strategies to control the cam position relative to the crankshaft (FIGURE 414).

FIGURE 4-14 The Toyota DS-4 intake and exhaust VVT control is used throughout the entire engine operating range to improve fuel economy, engine stability, and performance while reducing emissions. © Jones & Bartlett Learning.

Description

Valve overlap (the time when both the intake and exhaust valves are open at the same time) is reduced at engine start, stop, and idle for stability and reduced fuel consumption. Light load has the exhaust advanced and intake retarded to reduce compression blowback into the intake manifold and to improve engine stability. Medium load has the exhaust advanced and intake retarded to keep some of the exhaust gases in the cylinder for the internal exhaust gas recirculation (EGR) effect and reduces cylinder pumping losses for increased fuel economy and lower NOx emissions. Heavy engine loads at low to moderate engine rpm has the intake advanced and the exhaust retarded to improve filling the combustion chamber with air, resulting in higher torque output. High rpm and high load has the exhaust advanced and the intake retarded to further improve horsepower and torque to their maximum levels. Cold start has the exhaust cam at full advance and intake at full retard to eliminate valve overlap reducing blowback into the intake manifold and improving fast idle smoothness and stability. Research has improved GDI injector nozzle designs. Liquid gasoline does not burn; it must vaporize and mix with oxygen. Fuel pressurized at 1000 psi that passes through an opening 0.006″ to 0.011″ accelerates to 135 mph as a very fine mist with droplets that are 0.000003″ in diameter. This greatly increases the vaporization of the fuel with the benefit of absorbing heat in the process. Remember from physics that any change of state requires a great deal of energy transfer. The liquid fuel evaporating into a gas absorbs a great deal of heat energy in the process. This is what allows compression ratios as high as 12:1 on the Ford Coyote 5.0L V8 for very high power output. (Remember that VVT can be used to lower the static compression ratio depending on load to maximize fuel economy and reduce emissions.) The same strategy is employed on turbocharged GDI engines, where the forced induction raises combustion pressures and temperatures with the fuel vaporization absorbing heat to prevent detonation (FIGURE 4-15). The PCM functions to control the GDI pressure relief valve to provide the required pressure for the operation conditions of the engine. Controlling the pressure along with the injector ontime allows for one injector to deliver more than one spray pattern, using the type best suited for that range of engine performance. Using the PFI injectors provides additional flexibility. There is more than one way to make it all work together. For example, the Toyota DS-4 system uses PFI and GDI at idle and very light load, then all GDI through the mid-range, then both PFI and GDI at maximum load. Ford uses PFI at idle and light load with no GDI and then adds GDI as load increases while decreasing the PFI portion; however, it remains at about 5% to 10% of the fuel at the highest GDI use levels.

FIGURE 4-15 GDI injector spray patterns are affected by fuel pressure and nozzle design. © Jones & Bartlett Learning.

Description PFI and GDI injectors produce a great deal of underhood noise. The snap of the injector opening and closing can almost sound like a collapsed set of hydraulic valve lifters. This is one reason Ford operates the GDI injectors on its dual injection systems at only moderate to heavy load. The PFI injectors make less noise, and it is easier to dampen with an engine cover made of hard plastic with insulation as needed on the underside. Toyota uses GDI injectors through all of the engine operating conditions. On their 2.5-L engine they use a foam rubber engine cover to dampen the sound from the injectors (FIGURE 4-16).

FIGURE 4-16 GDI injector noise is a customer concern, so manufacturers make efforts to muffle the noise with engine covers. © Jones & Bartlett Learning.

Case Study: DS-4 PFI/GDI Diagnosis A 2018 Toyota Tacoma with a V6 DS-4 (PFI/GDI) injection system is running rough under load and the MIL is illuminated. The technician checks for DTCs and a misfire code, P0304, is stored. A review of the freeze frame shows the misfire occurred when the vehicle is in direct injection mode only, which on this vehicle occurs at moderate to heavy load. At other times, the PFI is also working and the engine runs with less roughness. The technician views misfire counts at idle in the shop bay and they are almost nonexistent at idle. The technician does a power brake test with the wheels off the ground using the lift. The misfire counts for cylinder 4 increase during the test. The technician performs a spark test on cylinder 4 and the results are okay; a good spark is present. The technician uses the scan tool active test to perform a compression test. (This test disables the fuel and ignition, then measures rpm changes as each piston is on the compression stroke with the starter cranking.) All cylinders are on specification. Good spark, good compression, fuel is the final component to check. The technician follows service procedures—no shortcuts on the high-pressure fuel system! A leak can be deadly, causing a fire during or after repair, and fuel under very high pressure can pass through the skin into the blood and cause severe complications or death. With the fuel rail removed for the affected cylinder bank (cylinders 2, 4, and 6), all injectors are within the 1.74 Ω to 2.04 Ω range. The technician swaps injectors 2 and 4, and using new seals, installs the fuel rail, fuel lines, and intake manifold. A test drive results in a P0302 DTC. The fault moves with the injector. Even though the ohm test was okay, it is not uncommon for an injector to still be failed or to fail once it reaches operating temperature with the engine heat. The technician removes the fuel rail again and takes the failed injector to the parts department. Toyota uses a small QR code on the injector that must be “read” along with the flow classification number to obtain another injector with the same flow rate (FIGURE 4-17).

FIGURE 4-17 When looking to replace the GDI injector, the technician should look at the QR code on the injector to verify that the replacement part will work at the same flow rate. © Jones & Bartlett Learning.

The technician installs all new seals on the three injectors and follows all installation procedures, including torqueing the fasteners. There are no shortcuts on GDI component installation. After installation of all components, the technician must perform learning value and idle learn reset procedures with the scan tool. Once this is complete, a test drive is performed based off the freeze frame of the original P0304 DTC. The engine runs smoothly and has normal power levels in all ranges, including under load. Fuel trim values are normal and there are no misfire counts on any cylinders. With the repair order documented, this vehicle is returned to the customer.

WRAP-UP Ready for Review The GDI system delivers fuel to the engine by opening an injector and spraying fuel directly into the combustion chamber. GDI components include the lift pump, high-pressure fuel pump, fuel delivery components, GDI injectors, and the PCM. Service information provides support for the strategic diagnostic process for PFI system inspection and testing. DTC service information includes problem symptoms tables, DTC diagnostics and component inspection, and removal and installation procedures. GDI diagnostic tools include the scan tool, the DMM, and the DSO. GDI fuel injector testing includes use of the scan tool active test to isolate if the injector is the possible cause of the fault. Fuel injectors can fail open or shorted. A shorted injector may cause the related injector driver in the PCM to fail, requiring both to be replaced. GDI injectors are selected for an engine based on flow rate and spray pattern and usually have a part or lot number stamped on them. Replacement injectors must match the original, and the part or lot number must match or a variety of engine performance concerns can result from use of the wrong injector(s). GDI injectors use a Teflon seal on the injector nozzle side. These seals are not reusable and must be installed with a special tool to prevent damage to them. GDI high-pressure fuel pumps are diagnosed by following the service information and using the scan tool data list and actuator/active test to isolate the cause of the fault. GDI high-pressure fuel pumps, fuel lines, and seals require following procedures as stated in the service information. Reusing seals, fuel line hardware, and fasteners when they are specified to be replaced can lead to fuel leaks, engine fires, and serious injury or death due to a high-pressure leak causing fuel to enter body tissue.

Key Terms Gasoline direct fuel injection (GDI) Engines that inject the fuel into the cylinder so that the PCM can inject the fuel at the optimum moment for efficient combustion. High-pressure fuel pump The engine-driven pump used on a GDI engine. Internal combustion engines (ICE) An engine that burns a fuel internally and creates movement due to thermal expansion of gases. PCM monitor OBD II monitor that runs continuously or noncontinuously throughout the drive cycle. Stratified charge mode A layering of a lean air-fuel mixture in the combustion chamber. It is used when the fuel injector and piston head place fuel near the spark plug but not the surrounding space. Variable valve timing (VVT) The advancement or retarding of individual camshafts to increase engine performance.

Review Questions 1. Direct injection injectors may operate using which of the following? a. Resistive capacitance b. 11 to 14 V c. Static voltage spikes d. Piezoelectric crystals 2. What is the fuel pressure operating range of GDI injectors? a. 500 to 3000 psi b. 45 to 65 psi c. 100 to 300 psi d. 800 to 2200 psi 3. GDI injectors are usually controlled: a. through a common ground for all injectors. b. through a common source for all injectors. c. through a dedicated injector subcontrol module. d. by a source and ground provided by the PCM. 4. All of the following are correct fuel injection system statements EXCEPT: a. Most injection systems use a homogeneous fuel charge. b. Injectors are controlled by turning on source voltage. c. Stratified fuel charges are very rich for high power. d. A homogeneous mixture is injected during the intake stroke. 5. One bar of pressure equals how many psi? a. 14.5 psi b. 10 psi c. 9.3 psi d. 4.7 psi 6. The GDI high-pressure fuel pump operates from which of the following? a. 12-V electric motor b. HV electric motor c. Camshaft lobe d. Crankshaft eccentric 7. GDI lift pumps operate using which of the following? a. 12-V electric motor b. HV electric motor c. Camshaft lobe d. Crankshaft eccentric 8. GDI direct injector to cylinder head seals are usually made of which of the following? a. Nylon b. Neoprene rubber c. Teflon d. Copper seal rings 9. Some GDI engines use which of the following (not usually found on a PFI engine)? a. Exhaust gas temperature sensor b. Injector flow rate sensor c. Narrow band oxygen sensor d. Variable valve timing

10. All of the following can affect GDI engines EXCEPT: a. intake valve deposits. b. injector fouling. c. high NOx levels. d. lift pump failure due to using incorrect grade of engine oil.

ASE Technician A/Technician B Style Questions 1. Technician A says GDI injectors can be tested with a noid light. Technician B says some GDI engines also use PFI injectors. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B 2. Technician A says GDI injector seals are usually made of Teflon. Technician B says GDI Teflon injector seals are reusable. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B 3. Technician A says GDI Teflon seals usually require a special tool for installation of the seal onto the injector. Technician B says some GDI injectors are coded to ensure flow rates are matched for all injectors? Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B 4. Technician A says the small dish area on some GDI engines is for the stratified fuel charge. Technician B says the stratified charge is used for high load operating conditions. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B 5. A vehicle is in the shop for a crank but no-start condition. Technician A says using throttle body cleaner sprayed into the intake could quickly verify a fuel or ignition fault. Technician B says you can usually hear the lift pump prime when the door opens or when the key is turned to the ON position. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B 6. Technician A says the lift pump can be checked for fuel pressure like a PFI fuel pump on most GDI engines. Technician B says a failed high-pressure fuel pump will always result in a crank but no-start condition. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B 7. Technician A says GDI high-pressure lines and injector fitting hardware can be reused if service is required. Technician B says use of the wrong engine oil can cause a high-pressure fuel pump failure. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B

d. Neither Technician A nor Technician B 8. Technician A says the high-pressure system must be depressurized before service. Technician B says some GDI systems may require a wait period before working on the system’s high-pressure components. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B 9. Technician A says the lift pump controls fuel pressure in the GDI system. Technician B says a failed lift pump will create a crank but no-start condition. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B 10. Technician A says the PCM controls voltage, usually through duty cycle, to the high-pressure fuel pump pressure regulator to control fuel system pressure. Technician B says excessive fuel pressure could indicate a faulty fuel pressure regulator. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B

© Jones & Bartlett Learning.

CHAPTER 5

Advanced Ignition System Diagnosis LEARNING OBJECTIVES After studying this chapter, you should be able to: 5-1

Describe OBD II ignition system components and operation.

5-2

Test the coil-on-plug (COP) ignition system for proper operation.

5-3

Inspect spark plugs.

5-4

Inspect ignition system spark plug wires.

5-5

Inspect the operation of crankshaft and camshaft position sensors.

5-6

Inspect engine protection devices and other factors affecting ignition timing.

5-7

Diagnose ignition system faults with DTCs.

5-8

Diagnose ignition system faults without DTCs.

YOU ARE THE AUTOMOTIVE TECHNICIAN A 2018 Toyota Camry comes into your service facility with DTC P0304, misfire cylinder 4. Upon verification of the concern, which of the following inspection procedures would be required as part of this vehicle fault diagnosis, and in which order? Verify source voltage to the ignition coil. IGT signal present. IGF signal present. Inspect the spark plug on that circuit. Measure spark plug wire resistance for that cylinder. Verify spark with a spark tester. View CKP signal with an oscilloscope. View CMP signal with an oscilloscope. Perform a compression test. Perform a cylinder leak down test. The technician’s knowledge of what may cause an ignition-related concern is demonstrated by applying strategy-based diagnostics. This chapter builds on the technician’s ignition system knowledge with a focus on how the related service information and testing procedures lead them to the cause of the fault.

Describe OBD II Ignition 5-1 Describe OBD II ignition system components and operation.

With the coming of OBD II, the ignition systems on modern vehicles are constantly monitored for failures and poor performance. When an ignition performance issue occurs, the OBD II system should flag this issue by setting a diagnostic trouble code (DTC). There are times when an ignition failure is not caught by the powertrain control module (PCM), which requires the technician to use their diagnostic skill sets to determine where to start and how to test those systems that are related to the ignition system. They must then propose a repair procedure to put the engine back into service. Like every gasoline-powered internal combustion engine, the air-fuel mixture, compression, and ignition are required for every event (FIGURE 5-1). Missing one of those items causes the engine to operate incorrectly or inefficiently.

FIGURE 5-1 The most common OBD II ignition system is the coil-on-plug type. This ignition system allows for precise ignition operation within the needs of each individual cylinder. © Jones & Bartlett Learning.

OBD II ignition systems function essentially the same as systems in vehicles built before 1996. The biggest difference is the addition of misfire monitoring by the engine control module/powertrain control

module (ECM/PCM). The components essentially remain the same and include the following: Ignition coil, either waste spark, coil on plug (COP), or coil near plug (CNP) Spark plug Spark plug wire Crankshaft position sensor Camshaft position sensor Knock sensor ECM/PCM The requirement that OBD II monitors for random and specific cylinder misfires fostered a quick change to COP ignition systems by most manufacturers. There were some OBD II vehicles that used waste spark systems. Most vehicles have been using COP systems since the early 2000s. No matter which system, the spark is still created by turning OFF the ignition coil to take advantage of the collapsing magnetic field in the primary coil. The primary side of the coil is turned ON with a source voltage of approximately 13 to 14 V. This creates a strong magnetic field in the ignition coil primary winding (FIGURE 5-2).

FIGURE 5-2 Most OBD II level vehicles use an ignition coil for each spark plug, called coil-on-plug ignition. © Jones & Bartlett Learning.

Description The PCM opens the primary coil circuit, and the magnetic field collapses into the secondary coil winding and is transformed into a very high voltage of 40,000 to 50,000 V. This high voltage is necessary

to push the electrons across the spark plug electrodes to create the spark, which ignites the very lean air-fuel mixture used in today’s engines (FIGURE 5-3).

FIGURE 5-3 The use of COP systems has increased in the later-model engine market because of the precision required to meet emission standards that are constantly getting more stringent. Along with decreased emissions, these systems increase performance by precisely controlling when the spark happens within the combustion event. © Jones & Bartlett Learning.

Description The OBD II ignition system operates as follows: The ECM/PCM supplies source voltage to the ignition coils when the ignition is ON. Cranking the engine with the starter allows the crankshaft position (CKP) sensor to generate a signal for crankshaft speed and a synchronization signal so the ECM/PCM can identify cylinder 1. The camshaft position (CMP) sensor generates a signal so the ECM/PCM can identify which cylinder is approaching its power stroke so the proper coil can be triggered. The ECM/PCM turns OFF the coil approximately 0.002 second before the piston is at top dead center (TDC). The coil transforms source voltage to the required high voltage to push the electrons across the spark plug electrode gap. The spark ignites the air-fuel mixture. The ECM/PCM monitors crankshaft speed during each spark event as part of the misfire monitor. Some systems use a circuit in the ignition coil to determine that the spark occurred and supplies this data to the ECM/PCM for misfire monitors. The ignition system turns OFF when the vehicle ignition switch or engine start/stop button is used to turn the engine OFF.

TECHNICIAN TIP Many vehicles are integrating a stop/start feature on vehicles. The ECM/PCM monitors engine idle time and other factors, such as engine temperature and battery voltage, to stop the engine to save fuel when waiting at a stop light. The engine is turned OFF by the ECM/PCM by cutting source voltage to the ignition coils and fuel injectors. The ECM/PCM restarts the engine as the driver removes pressure from the brake pedal. Most of these systems use a heavy-duty battery and starter to provide this function. Some stop/start systems operate the ignition coils based on which cylinder is about to fire to get the engine started.

Stop/start technology and hybrid vehicles rely on the ignition system to help with continuous vehicle starting and stopping. The stop/start technology allows the engine to shut off at intersections and other situations where there is an extended idle time. Once the driver moves the foot off the brake and onto the gas pedal, the starter, ignition, and fuel system work in unison to start the engine quickly. This is similar to the initial startup of the vehicle but continues to happen as the vehicle is driven. This puts extra load on the ignition system and requires the components to be up to the challenge. Hybrid vehicle ignition systems are similar in that they operate independently of the vehicle driving, which can also require more robust components. The unique hybrid internal combustion engine (ICE) operates at a lower load capacity than the conventional vehicle because the ICE is used for power generation in conjunction with the electric motor. This allows it to run at a steady rpm. With all of these components working in concert with each other, one failed component can cause the whole system to fail, resulting in a misfire or a no-start condition. When inspecting ignition components, the technician should be looking for properly installed, quality components that have not been modified.

Ignition System Spark Testing 5-2 Test the coil-on-plug (COP) ignition system for proper operation.

Diagnosing an ignition issue related to an engine performance concern requires the technician to verify the different sections of the ignition system for operation. The first thing that should be addressed is whether the engine can produce a quality spark across the spark plug gap. To produce this spark, the ignition system voltage, trigger, and control must be maintained to keep the engine operational. When developing a strategy to diagnosis a misfire or engine ignition issue, the technician should first look to verify whether the engine can produce a spark. This can be done by removing the spark plug wire or COP and hooking up a spark tester that will allow the technician to physically see the spark outside the engine cylinder (FIGURE 5-4). The spark test allows you to determine quickly whether a spark is present from one ignition coil or coil pack. This test is often used when an engine cranks but does not start or if the engine runs but one cylinder has a misfire DTC. The tester can be a fixed type of tester or it can be adjustable, which allows the technician to adjust the gap to verify the coil can create the necessary spark to operate on a varying operational condition (FIGURE 5-5). To use a spark tester to verify spark on a vehicle, follow the steps in SKILL DRILL 5-1.

FIGURE 5-4 The spark test can quickly verify whether the ECM/PCM and ignition coil are functioning. © Jones & Bartlett Learning.

FIGURE 5-5 Using an adjustable spark tester, the technician can vary the required gap to load the ignition coil to verify operational integrity through a varying range of loads. © Jones & Bartlett Learning.

SKILL DRILL 5-1 Using a Spark Tester to Verify Ignition System Spark

1. Remove the ignition coil of the misfiring cylinder, or the easiest to access, for a crank but no-start condition.

2. Install the spark tester and make sure it is connected to a good ground.

3. While the engine is being cranked, watch or have someone watch the spark tester to see whether the coil produces a spark.

4. If using an adjustable spark tester, test the coil’s ability to generate quality spark at varying gaps. This tells the technician the coil has the ability to produce varying amounts of voltages based on ignition system need.

5. If spark does not happen, the technician should start the diagnostic testing based on no-start, no-spark strategies.

6. Crank the engine to verify whether a spark is present. © Jones & Bartlett Learning

Testing Spark Plug and Ignition Coil Operation Without Coil Disassembly Another type of spark test tool may be used to determine whether the COP-type ignition coil is being turned OFF by the ECM/PCM to create a spark event. As you have learned throughout your training with CDX, secondary ignition coil voltage is developed based on the law of induction. The primary coil, in the ignition coil, is powered up until it is turned OFF by the trigger device. Once power is turned OFF to the primary coil, the electromagnetic field collapses onto the secondary coil, which then, because of the increased windings, jumps up the voltage to 30,000 to 50,000 V, which is used to jump the spark plug gap. When this voltage event happens, it gives off an electromagnetic field that can be read by an ignition coil wand. The kilovolts (kV) that are given off by the collapse event in the coil allows the wand to determine the amount of kilovolts that the spark needs to jump the gap. Increased kilovolts can be a sign of a worn-out spark plug, a damaged coil, or a potential excessive lean condition. This tool can be used to expedite the rate at which the technician can pinpoint the failure within the cylinder. Once it is determined that the coil is producing excessive kilovolts to operate the spark plug, the technician can home in on what can affect that cylinder causing the failure. The ignition coil wand comes in various configurations depending on what the technician is trying to accomplish. The basic handheld wand activates (turns ON) by lightly tapping it on a firm surface. Place the flat end of the tool on the coil of the misfiring cylinder. The LED indicator in the tool handle will flash in sync with the ignition trigger events (FIGURE 5-6). The limitation of this tool is that it does not allow you to verify that a spark is occurring or whether the spark is strong enough to ignite the air-fuel mixture in the cylinder. A higher priced version uses a handheld unit that provides more information, including spark

duration time and voltage, which can prove very useful considering that the technician is often working with engine designs where the spark plug coils are very difficult to remove (many V-type engines in front wheel drive applications require removing the intake manifold to access the ignition coils and spark plugs on the rear bank of the engine) (FIGURE 5-7).

FIGURE 5-6 Tools are available to determine whether the ignition coil is turning OFF and creating a collapsing magnetic field. This handheld tool shows whether the coil is firing but does not tell the technician whether the spark is being generated across the spark plug gap. © Jones & Bartlett Learning.

FIGURE 5-7 Some coil-on-plug testers provide spark duration time and spark voltage data, which can be useful for the technician when determining what the next step in the diagnosis should be. © Jones & Bartlett Learning.

Description If the coil is okay, use the wiring diagram and follow the service procedures to check for the ignition trigger signal (coil ground goes open). Use of an oscilloscope is recommended for this test (FIGURE 5-8) showing a normal trigger signal. A voltage that is steady near source voltage levels can indicate a wiring harness fault between the coil and the ECM/PCM or a failed coil driver (transistor) in the ECM/PCM. You can determine a wiring harness fault by measuring continuity on the trigger wire between the coil and the ECM/PCM connectors. The resistance should be very close to 0 Ω. High resistance or OL indicates a wiring harness fault and may require a harness repair or replacement. A normal reading near 0 Ω indicates that the ECM/PCM has a bad driver and must be replaced. This condition is rare, but when it does occur, most manufacturers recommend also replacing the related ignition coil (and if applicable, spark plug wire) for the affected cylinder. A shorted ignition coil primary winding allows too much current in the circuit, causing the coil driver transistor to fail. Replacing only the ECM/PCM and leaving a bad coil leads to a very expensive replacement the second time around.

FIGURE 5-8 The blue signal is the ignition trigger for cylinder 1. Proper PCM ignition coil actuation can help the technician eliminate the PCM as a cause of the misfire on the cylinder. A digital storage oscilloscope (DSO) is a good tool to show a graphical representation. Courtesy of Pico Technology Ltd.

If no spark is present for a no-start condition, you must follow the service information diagnostics to isolate the cause. The fault may be related to the circuit supplying source voltage to the coils, lack of a CKP signal to the ECM/PCM, or a damaged vehicle wiring harness. A no-spark condition at a coil related to a cylinder misfire DTC may be caused by a faulty coil, a wiring fault on the ground side of the coil to the ECM/PCM, or with the ECM/PCM coil driver circuit. You can swap coils to determine quickly whether the coil is at fault.

Inspect Spark Plugs 5-3 Inspect spark plugs.

Spark plug inspection is usually done when there is a cylinder misfire but the coil passed the spark test or when there are random cylinder misfires and vehicle mileage indicates the spark plugs may have exceeded their operating life. Most new vehicles are equipped with platinum or iridium plugs, which can last up to 100,000 miles or more. Wear is indicated when the electrodes no longer have their “as new” shape (FIGURE 5-9). A worn spark plug is replaced with a new one of the correct part number. This ensures the plug has the correct thread length, heat range, and electrode type. Follow installation procedures, which may include the use of a small amount of antiseize on the threads, and always torque to specification. Platinum and iridium plug electrodes are not adjustable and are packed with electrode protectors. Attempting to adjust the electrode can damage the electrode protective coating, and the plug may misfire or have a shorter than normal service life.

FIGURE 5-9 Spark plug life lasts many thousands of miles, but those miles cause electrode wear. Note the new plug (A) compared to the one with very high mileage (B). © Jones & Bartlett Learning.

Description The spark plug insulator can be damaged if the spark plug is dropped or if it is installed or removed incorrectly. Using the wrong type of socket or having the socket at the wrong angle can damage the insulator during service. The high voltage can travel through the insulator to ground, bypassing the spark plug electrodes. This condition can also allow higher than normal current levels that cause a coil to fail. Dirt or other contamination on the insulator can allow the high voltage to travel along the surface of the insulator to a ground point at the base of the plug. This can cause a misfire condition and can also lead to coil damage. Look for a dark line that ends where the insulator attaches to the metal housing of the plug (FIGURE 5-10). Inspect the plug boot for damage. This condition is usually corrected by replacing the spark plug and coil boot (or spark plug wire if a waste spark system).

FIGURE 5-10 A damaged spark plug insulator can cause a cylinder misfire condition, allowing the spark to jump to ground without jumping the electrode gap. © Jones & Bartlett Learning.

Spark plugs also tell a story related to what is happening in each cylinder. Oil fouling can indicate worn piston rings or valve guides. Carbon fouling indicates a rich mixture, whereas very white or light electrodes and insulator surfaces indicate a lean condition. Coolant intrusion into the cylinder damages the electrode to the point that it would cause a misfire. Physical damage may indicate use of the wrong fuel or faulty knock sensor, leading to spark knock, or there could be a mechanical issue, such as a broken valve, in that cylinder (FIGURE 5-11). Spark plugs that tell a story other than that they had a good long life are your indication to continue your diagnosis to isolate the cause of their abnormal condition.

FIGURE 5-11 Spark plugs tell a story for each cylinder. It may be running very lean or there may be oil getting into the cylinder based on the condition of the spark plug electrodes and insulator. © Jones & Bartlett Learning.

Description TECHNICIAN TIP

Misfire DTCs that cannot be duplicated or show as history can be caused by use of the wrong fuel, such as E85, or contaminated fuel. The customer continues to drive and upon filling up the vehicle with the correct fuel, the misfires begin to become less frequent. It is important that you or the service advisor discuss this possibility with the customer. Use of the correct fuel may seem to resolve the issue; however, the customer should be made aware that the use of ethanol in the fuel system above the manufacturer’s limits can lead to fuel system damage, especially damage to injector seals, flexible fuel lines, and the fuel pump assembly.

Analyze Spark Plug Failure Using the spark plug pulled out of the cylinder that is having the running issue, the technician should not just replace the spark plug if the plug shows signs of a nonwear failure. If the spark plug shows signs of being exposed to contaminants from outside the combustion chamber, the technician should diagnosis those items before moving on. Failure to fix the root cause of the contamination can eventually lead to the same failure repeating itself. When investigating a cooling system failure, the technician should start by determining the integrity of the cylinder. Cylinder integrity is something that will need to be verified by conducting mechanical testing on the cylinder. This can include compression, leakdown testing, and oil consumption testing. Along with a mechanical engine failure, fuel injection components can either leak or be falsely commanded ON, causing the cylinder to become rich and foul out the spark plug. It is important to look at the engine as a whole and to determine the cause of the failure to properly repair the engine misfire or failure. A well-used spark plug can give the technician an insight into the combustion process in the engine and how well the engine is operating. Reading the spark plugs can also indicate the quality of fuel present in the vehicle. This may indicate whether poor fuel quality is the root cause of an engine misfire. Everything must work together to maintain proper engine operation. To maintain the ability of the engine to create enough power, proper quality of components must be maintained. The increasing precise requirements of emission standards require more efficient engine operation.

Inspect Spark Plug Wires 5-4 Inspect ignition system spark plug wires.

Most of the vehicles you see in your service bay will have COP ignition. There were some OBD II level vehicles that used a waste spark system, and there are some cam in block engines, such as the GM Vortec engine series, that use one coil per cylinder but use a spark plug wire to connect the coil to the spark plug (FIGURE 5-12). For use of the spark plug wire in this application, the position of the ignition coil can be moved to the valve cover away from the hot exhaust manifold.

FIGURE 5-12 Some OBD II level vehicles use spark plug wires to connect the coil to the spark plug. © Jones & Bartlett Learning.

Spark plug wires should be inspected for visible signs of voltage leaking to ground, physical damage, and resistance (FIGURE 5-13). Visually inspect each plug wire for signs of arcing, which usually leaves a light-colored area on the plug insulation (FIGURE 5-14). The wire insulation breaks down over time due to heat cycling in the engine compartment. Also, improper wire routing that allows the wires to touch each other or any metal surface directly can cause this condition. It may be difficult to visually locate an arcing wire by trying to find the signature arc point. You can use a spray bottle filled with water and lightly spray the wires while the engine is running. Do this in an area that is dimly lit and look for visible arcing. The spark plug wires should be replaced if arcing is present.

FIGURE 5-13 Spark plug wire insulation can fail over time, causing the high voltage to take an easier path to ground by arcing across to another wire or directly to any metal that has a path to ground. © Jones & Bartlett Learning.

FIGURE 5-14 Spark plug wire inspection includes a visual check and measuring resistance to determine whether the wire is serviceable. © Jones & Bartlett Learning.

Similar to COP systems, some plug wires used on overhead cam (OHC) engines can have arcing issues within the spark plug well (FIGURE 5-15). Water or oil in the well can cause this condition, as can plug wires that have degraded and reached the end of their service life. Water in the spark plug well can also cause the plug wire terminal to corrode, causing a poor connection with the spark plug terminal creating a misfire. Oil leaks are caused by failing rocker cover gaskets and plug well seals. These conditions must be corrected to prevent the new plug wire from premature failure. Correct any oil leaks and, if water was present, discuss this with the vehicle owner. The owner should know that washing the engine with pressurized water can lead to this type of failure.

FIGURE 5-15 Spark plug wire boots on OHC engines can have arcing faults in the spark plug well similar to a COP system. These “cracks” in the material allow spark current to leak from the spark plug boot. © Jones & Bartlett Learning.

Spark plug wires that pass the visual inspection are then checked for correct resistance. The typical spark plug wire has about 1000 Ω of resistance per foot; however, you should always refer to the service specifications for the vehicle you are working on (FIGURE 5-16). Some manufacturers provide a range with a low and high value. Measure spark plug wire resistance with your digital multimeter (DMM) by placing one lead on the coil end and the other at the spark plug end. Wires that are too high or too low are out of specification and should be replaced. If one or more wires are out of specification, they are usually replaced as a set.

FIGURE 5-16 Some spark plug wire resistance specifications are found in the service information. If none are found, verify by comparing all of the spark plug wire readings on the engine. © Snap-on Incorporated.

Description This ensures that the coil end matches up to the correct cylinder at the spark plug end. Remove one wire at a time and match it up to the wires in the set, then locate the wire that is the same length. Most manufacturers recommend using dielectric grease on the spark plug wire ends (FIGURE 5-17). This helps ensure smooth installation, can improve terminal contact connections, and make removal easier should it be needed during future service. Many spark plug wire sets include a small amount of dielectric grease for this purpose. It is important that the spark plug wires are routed using all the factory installed retainers. These retainers keep the plug wire from vibrating and away from heat sources, both of which can damage the insulation and lead to a short to ground before the high voltage reaches the spark plug. To inspect spark plug wires, follow the steps in SKILL DRILL 5-2.

FIGURE 5-17 Many manufacturers recommend using dielectric grease when installing new spark plug wires. This helps seal the connector, ease installation and removal, and maintain the integrity of the components. © Jones & Bartlett Learning.

SKILL DRILL 5-2 Inspecting Spark Plug Wires 1. Access the spark plug wire inspection procedure for your assigned vehicle. If your instructor has provided a spark plug wire to test, use the general specification of 1 kΩ/foot (1000 Ω/foot). 2. Set the DMM to measure resistance. 3. Place one lead at the coil end of the wire and at the spark plug end, making sure the DMM lead is touching the wire contacts. 4. Note the resistance value on the DMM. 5. Measure the length of the spark plug wire and determine whether it is within specification. Review your findings with your instructor.

Inspect CKP/CMP Sensors 5-5 Inspect the operation of crankshaft and camshaft position sensors.

The CKP sensor is a critical sensor, and working with the CMP sensor allows the ECM/PCM to determine crankshaft speed and synchronize fuel and ignition output control. A CKP sensor or circuit fault usually results in a crank no-start condition or, if the engine was running, it will stop. The ECM/PCM cannot control the ignition coils or the fuel injectors without this signal (FIGURE 5-18).

FIGURE 5-18 Crankshaft position sensors provide data so the ECM/PCM can operate the spark output signals at the correct time for each cylinder. © Jones & Bartlett Learning.

Most CKP sensors are one of two types: magneto reluctance (MR) or magneto resistive/Hall

effect (MRE). The MR type produces an analog A/C voltage sine wave signal using a two-wire sensor. The MRE type produces a digital square wave signal using a three-wire sensor (FIGURE 5-19). CKP sensor testing begins with a review of the related service information to determine the type of sensor on the vehicle, test procedures, and wiring diagram. Following the strategy-based diagnostic process, you can quickly isolate if a crank no-start condition is related to the CKP sensor as part of step 3, focused testing, by viewing scan tool data for the engine speed parameter ID (PID). Crank the engine and note the scan tool data (FIGURE 5-20). A reading of 0 rpm indicates there is no CKP data to the ECM/PCM. On some vehicles you can also look at the tachometer, if equipped, and see whether it registers rpm during engine cranking. If the scan tool data show engine rpm during cranking, then the CKP sensor and circuit are most likely operating, but that does not mean they are operating correctly.

FIGURE 5-19 Each type of crankshaft position sensor produces a signal that can be interpreted by the PCM to control ignition and fuel events. If the sensor becomes inoperable, then the engine will not be able to control these events, causing it not to operate. © Jones & Bartlett Learning.

Description

FIGURE 5-20 Using a scan tool in the data menu can help the technician decide where to start looking for the cause of the nostart condition. © Jones & Bartlett Learning.

Description Recall that there are two major types of CKP sensors: magneto reluctance and magneto resistive. Inspect each as follows: CKP sensor DSO testing an MR type sensor: Magneto reluctance sensors output an alternating current (AC) signal with a synchronization gap in the signal (FIGURE 5-21). Set the DSO to view an AC signal with a voltage range of 4 V/division and a time scale of 20 ms/division for this example.

FIGURE 5-21 CKP signal as viewed on a DSO for a magneto reluctance type sensor. The gap indicates the synchronization notch for TDC of cylinder 1 for most vehicles. Courtesy of Pico Technology Ltd.

Connect the positive scope lead to the positive signal wire and the negative lead to the negative signal wire based on the wiring diagram (FIGURE 5-22). Abnormal signals will have low output, abnormal gaps, or no signal at all.

FIGURE 5-22 A failing MR sensor cannot generate the proper AC voltage output and should be closely inspected to verify that something else is not causing the failure. If it is determined the sensor is the cause of the low signal condition, replace it with a quality component to maintain ignition system operation. © Jones & Bartlett Learning.

Description Magneto resistive-type CKP sensors are usually three wires and often feature Hall-effect digital signal output (FIGURE 5-23). Connect the positive DSO lead to the CKP signal wire and the negative lead to the CKP ground. The output is a square wave signal with one or more synchronization gaps in the signal (FIGURE 5-24). Abnormal signals will have low output, abnormal gaps, or no signal at all. Verify that circuit voltages correspond to service information specifications and that there are no voltage drops in the wiring. Replace a faulty CKP sensor or repair a fault in the wiring as required.

FIGURE 5-23 On an MRE sensor, the sensor is powered by the PCM so it can generate a square wave signal as an output. © Jones & Bartlett Learning.

FIGURE 5-24 Magneto resistive CKP sensors are usually three-wire sensors and output a digital signal. © Jones & Bartlett Learning.

Description MR CKP sensor inspection usually includes measuring resistance of the sensor (FIGURE 5-25). Use the DMM to measure the resistance and compare to service specifications. A sensor that is OL or has very close to 0 Ω will need to be replaced. If resistance is within specifications, you can then check for an output signal with the DMM. Set the DMM to AC voltage, then crank the engine with the DMM leads connected to the CKP sensor connector pins (FIGURE 5-26). A reading of 0 AC volts indicates no signal voltage is being generated and the sensor should be replaced. Obtaining a voltage reading that increases with engine rpm may be okay. You can be sure by using an oscilloscope to view the CKP signal (FIGURE 5-27).

FIGURE 5-25 MR-type CKP sensors can be checked for resistance and compared to service specifications. © Jones & Bartlett Learning.

FIGURE 5-26 A quick test is to hook up a voltmeter to the MR sensor, and in AC voltage mode the sensor should generate a voltage. If the voltage is low or nonexistent, then the sensor is not operating properly. © Jones & Bartlett Learning.

FIGURE 5-27 A DSO is a better tool for verifying proper operation of the MR sensor. It gives the technician a graphical representation of what the sensor is producing, which can then be used to explain the failure to the customer. © Jones & Bartlett Learning.

MRE sensors may be used for CKP sensor signal generation and most CMP sensor signals (FIGURE 5-28). The MRE sensor outputs a digital DC signal. An MRE CKP sensor signal is required for the engine to start and run. Like the MR type, you can use the scan tool to view engine speed data during cranking. A reading of 0 rpm indicates that there is no signal reaching the ECM/PCM or a fault in the ECM/PCM. The MRE sensor has three wires: one is ground, one is source voltage, and the other is the signal wire. Follow service inspection procedures to verify that the sensor has a good ground (remember the circuit must be ON with current present to check voltage drop) and correct voltage. If the ground or source voltage is out of specification, correct the fault in the harness or ground point. If those are okay, you will need to use a scope to check for signal output. Connect the scope to signal ground and the MRE signal wire and set the voltage and time divisions as specified (FIGURE 5-29).

FIGURE 5-28 The MRE sensor uses a voltage reference signal from the PCM, which is then used to generate a signal return from the PCM based on the position of the component. These types of sensors are commonly used for CMP sensors. Courtesy of Pico Technology Ltd.

Description

FIGURE 5-29 The MRE CKP/CMP signal is a square wave digital signal. There may be more than one sync gap depending on trigger wheel design. This type of sensor gives the PCM an exact ON or OFF position, which increases the ability of the PCM to make correct decisions. Courtesy of Pico Technology Ltd.

Description The CKP or CMP signals should look like the samples provided in the service information. The square wave should be clean and indicate the correct number of reluctor teeth. CKP signals have a synchronization notch. CMP signals are usually spaced out using different reluctor tooth sizes to provide camshaft position data to the ECM/PCM. A faulty signal, or no signal, can indicate a faulty sensor that should be replaced. If you have a good signal, check the signal wire at the ECM/PCM using the scope. If there now is no or a faulty signal, there is a wiring fault. If the signal is okay, the ECM/PCM may be faulty. Most CKP and CMP sensor mounting does not allow for any type of adjustment. Use of an incorrect part can cause a fault, as it may place the magnet area of the sensor too far or too close to the trigger source. A sensor that is too far from the reluctor is indicated by lower signal voltage output than normal. A sensor that is too close to the reluctor usually ends up damaged by the reluctor due to contact with it, so it does not produce any signal. A loose or missing CKP or CMP sensor mounting fastener can cause misalignment of the sensor to the reluctor or allow the sensor to move or vibrate while the engine is running, causing an erratic signal that results in abnormal ignition coil trigger signals. Verifying the correct part and a correctly installed part should be done as the technician is completing the diagnostic routine. To observe the CKP sensor signal on a DSO, follow the steps in SKILL DRILL 5-3. To observe the CMP sensor signal on a DSO, follow the steps in SKILL DRILL 5-4.

SKILL DRILL 5-3 Observing the CKP Sensor Signal on a DSO

1. Access the service information for the CKP sensor inspection procedure and related wiring diagram for your assigned vehicle.

2. Determine whether the sensor is an MR or MRE type. MR will be an AC sine wave and MRE will be a DC square wave signal. Set the DSO voltage and time units to those recommended in the service information.

3. With the ignition and engine OFF, back probe the CKP sensor connector to connect the DSO. MR sensors usually connect each lead to the related positive and negative signal of the connector. MRE sensors require the positive lead to connect to the sensor signal terminal and the negative lead to a known good ground.

4. Verify that the test leads are not near any of the accessory drive pulleys and belts and are clear of any heat-generating components, such as the exhaust manifold.

5. Start the engine and view the display. Verify that the signal pulses on the display match the service information. Note any trigger pulse(s). Verify your work with your instructor.

6. Turn the engine OFF. Carefully remove the test leads and back probe tools. Return all equipment to its storage location. © Jones & Bartlett Learning

SKILL DRILL 5-4 Observing the CMP Sensor Signal on a DSO

1. Access the service information for the CMP sensor inspection procedure and related wiring diagram for your assigned vehicle.

2. Determine whether the sensor is an MR or MRE type. MR will be an AC sine wave and MRE will be a DC square wave signal. Set the DSO voltage and time units to those recommended in the service information.

3. With the ignition and engine OFF, back probe the CMP sensor connector to connect the DSO. MR sensors usually connect each lead to the related positive and negative signal of the connector. MRE sensors require the positive lead to connect to the sensor signal terminal and the negative lead to a known good ground.

4. Verify that the test leads are not near any of the accessory drive pulleys and belts and are clear of any heat-generating components, such as the exhaust manifold.

5. Start the engine and view the display. Verify that the signal pulses on the display match the service information. Note any trigger pulse(s). Verify your work with your instructor.

6. Turn the engine OFF. Carefully remove the test leads and back probe tools. Return all equipment to its storage location. © Jones & Bartlett Learning

Inspect Ignition Timing 5-6 Inspect ignition timing and engine protection devices.

Base ignition timing adjustment was at one time part of an annual engine tune-up. Those days have long passed. Most OBD II vehicles have no timing adjustment and, as a technician, you can reference ignition timing from the scan tool data list only. A poorly running engine may have an ignition timing issue. Correct ignition timing depends on all other mechanical and input signal data being correct. Compare the ignition time data on the scan tool with the specifications in the service information and follow the applicable diagnostic procedures if the timing is not correct. Some possible causes for inaccurate ignition timing include the following: PCM fault that may be corrected with a software update CKP or CMP sensor fault Damage to shielded wiring for CKP or CMP sensors Knock sensor fault Damage to knock sensor shielded wiring Timing belt or timing chain improperly timed between crankshaft and camshaft(s) The PCM causing an ignition timing fault is very rare. The most likely issue may be an error in the ignition-operating software program that could be corrected with a software update. Check for software updates as part of the strategy-based diagnostic process step 2, review related service information. Inspect the CKP, CMP, and knock sensors for proper operation and verify that there are no fault codes related to their operation in the PCM. Verification of a timing chain or timing belt that is off by one tooth or more varies depending on engine design. Refer to the related service information and set the crankshaft to TDC when cylinder 1 is on the compression stroke. You will have to verify that the camshaft or camshafts are in their correct positions. This condition can lead to a crankshaft to camshaft sensor correlation DTC (FIGURE 5-30). You may have to remove the time cover or rocker cover(s) to verify that the timing belt or timing chains are timed correctly. It is recommended that all other possible causes have been eliminated before doing focused testing on crank to cam timing due to the amount of time required for this inspection.

FIGURE 5-30 Having a base engine timing issue affects the operation of the ignition system as it will not be in time with the position of the crankshaft and pistons. © Jones & Bartlett Learning.

Verifying Knock Sensor Operation The knock sensor generates a signature signal when spark knock is occurring, similar to a microphone reacting to sound vibrations in the engine. When spark knock occurs, the sound wave signal is picked up by the knock sensor and sent as a voltage signal to the ECM/PCM (FIGURE 5-31). The knock sensor is critical in controlling ignition timing advance controlled by the ECM/PCM. Ignition timing is advanced between engine speeds of idle to about 3600 rpm to allow for about 0.002 second between the spark event and the piston reaching TDC on the compression stroke. The faster the engine speed, up to about 3600 rpm, the faster ignition timing must advance to allow the coil enough time to generate a spark at the spark plug electrodes to maintain the 0.002 second to ignite the air-fuel mixture necessary to obtain the maximum burn during the power stroke. A knock sensor circuit that is faulty can allow ignition timing to advance too rapidly or too far and create spark knock, where the burn event occurs while the piston is still moving up on the compress stroke (FIGURE 5-32). Severe spark knock can lead to engine damage, including cracked pistons or a broken connecting rod.

FIGURE 5-31 Using a piezo crystal to generate voltage based on vibration, the knock sensor controls ignition timing. If the base engine is not in operational condition, the knock sensor may pick up stray noises, causing the engine to retard the timing and thus creating a performance issue for the driver. © Jones & Bartlett Learning.

FIGURE 5-32 If the ignition event happens before the piston is at TDC, engine component failure can result as the increased pressures in the wrong situations will fatigue those components to failure. © Jones & Bartlett Learning.

Description Knock sensors are tested for continuity or resistance at a specified amount. Refer to the service information for specifications. Knock sensor data can be viewed on the scan tool. Some sensors may generate a signal if you lightly tap the engine block while viewing the scan tool data. Open or shorted sensor data values may store a DTC. DTC inspection procedures usually have you confirm that the knock sensor supply voltage and ground are okay. If they are, the sensor is most likely at fault and must be replaced. If there is no supply voltage or ground, perform continuity checks on the knock sensor circuit wiring. Wiring faults can be difficult to repair because these wires are usually shielded. It is best to replace the harness if there is a wiring fault. The knock sensor is a precision unit and will be damaged if dropped or struck by an object. On V-type engines, there may be one knock sensor per cylinder bank. The location of some knock sensors may require intake or other component removal to access the knock sensors for replacement (FIGURE 5-33). If one sensor has failed, it may be best to replace both because they are usually located in hard-to-access locations.

FIGURE 5-33 Some knock sensors require extensive disassembly to access the components. When this is required, it is recommended that the technician replace both knock sensors to minimize the possibility of the other knock sensor failing in the future. © Jones & Bartlett Learning.

DTC-Based Ignition System Diagnosis 5-7 Diagnose ignition system faults with DTCs.

Ignition system diagnosis usually begins when a misfire DTC is present. Verify the malfunction indicator lamp (MIL) is illuminated to begin the strategic diagnostic process, and note whether the engine is exhibiting any rough running and lack of power concerns common with a cylinder misfire condition. Use a scan tool to obtain any stored DTCs if the MIL is ON. A misfire DTC can lead you to a specific cylinder that has the misfire condition or random cylinder misfires that are occurring in most or all cylinders. An ignition-related fault isolated to one cylinder usually creates a DTC that identifies which cylinder is not firing. A misfire in cylinder 2 may generate a P0302 DTC. Here is how misfire DTC P0302 breaks down: P = Powertrain DTC 0 = Generic, not manufacturer-specific, DTC 3 = Ignition system 02 = Cylinder identification A misfire can have many causes. The service information lists 15 possible misfire causes. Your knowledge, the service information, the scan tool, the DMM, and application of the diagnostic process are used to isolate the cause. Ignition-related OBD II DTC-based diagnostics rely on following the service information inspection procedure (FIGURE 5-34).

FIGURE 5-34 Ignition system DTC diagnosis follows the inspection procedure flow chart. Using the flow chart allows the technician to diagnosis the ignition issue on the engine effectively.

It is critical that you, the technician, apply the diagnostic process and follow the steps of the inspection procedure. Making assumptions or skipping steps may seem like it will save time, but taking a

shortcut is likely to lead to an incorrect diagnosis or, worse, a come-back situation. Most DTCs store a freeze frame (FIGURE 5-35). The freeze frame data are valuable to your diagnosis. The data provide vehicle speed, engine load, engine speed, and other information that can help you duplicate the fault if it is not occurring with the vehicle in your shop stall. Review the data for any items that may provide a possible cause for the misfire condition or use it to create a similar condition during a test drive to determine whether the fault is currently present or is intermittent.

FIGURE 5-35 Freeze frame data can help you with information on vehicle speed, engine speed, engine load, and more, when the DTC stored. This allows the technician to operate the vehicle in the exact conditions in which the DTC was triggered and the event happened. © Jones & Bartlett Learning.

Description Description Review the live scan tool data and focus on the following: Fuel trim Misfire counts Engine coolant temperature (ECT) operation Ensure that fuel trim is within the normal range. An overly rich or lean mixture can affect ignition events and lead to a misfire condition. The misfire count data can let you know if the ECM/PCM is detecting a misfire event as the engine is running while in your shop stall. Verify the ECT is providing accurate coolant temperature data. Use an infrared temperature gun to verify accuracy. ECT data that are faulty may cause a lean condition on cold start or, if the temperature data remain below actual coolant temperature, it can cause a rich condition leading to spark plug fouling and a misfire condition.

DTC-Based Ignition System Diagnosis Case Study

A 1996 Ford Explorer with just over 96,000 miles is in the shop with the MIL ON. The technician verifies the MIL is ON and notes the 4.0-L V6 is running slightly rough. The scan tool is connected and DTC P0304 is the only one stored. The technician reviews the freeze frame and notes the vehicle was traveling at 23 mph with a calculated 25% load and at operating temperature when the DTC stored. The technician obtains the service information for this DTC (FIGURE 5-36).

FIGURE 5-36 Using service information to start your diagnostic procedure after you have verified the compliant should be done in all cases. The service information for the P0304 code will show the technician how to make the repair. © Snap-on Incorporated.

Description This engine uses a waste spark system with one coil supplying the firing voltage for two spark plugs (FIGURE 5-37). This engine pairs cylinders 3 and 4 on the same ignition coil. Both plugs fire when the piston in each cylinder approaches TDC, but one cylinder is on the beginning of the power stroke and the other is completing the exhaust stroke.

FIGURE 5-37 This vehicle is OBD II and uses three coils, which fire two spark plugs per coil. This is an example of a waste spark system. When one coil fails it affects the companion cylinder, thus causing not just one but two cylinders not to operate at 100%. © Jones & Bartlett Learning.

If the coil were at fault, there should be misfire DTCs for both cylinders 3 and 4. A check of scan tool misfire counts shows that cylinder 3 is operating normally whereas cylinder 4 has a rapidly advancing misfire count (FIGURE 5-38). From this information, the technician can rule out the ignition coil as the cause of the misfire. This vehicle uses spark plug wires so the technician deviates slightly from the service information to do a quick check to see if the spark plug wire has the high voltage present when the coil operates. The technician then performs a spark test, and the spark tester indicates there is normal spark present. Because cylinder 3 has no misfire and the cylinder 4 spark plug wire indicates that spark voltage is present, the technician removes the related spark plug. The spark plug is very difficult to remove, and inspection shows an odd buildup of material on the threads. The spark plug electrode and in-cylinder insulator appear fuel fouled. The technician inspects the cylinder for damaged spark plug threads, but they are okay. A new spark plug is installed, using a very light coating of antiseize lubricant on the threads. The technician places a small amount of dielectric grease in the spark plug boot and reinstalls the boot on the new plug.

FIGURE 5-38 The misfire counts show cylinder 3 is okay but cylinder 4 counts are increasing as the engine runs. Both cylinders share the same coil for this waste spark-type ignition system. © Jones & Bartlett Learning.

Description The technician turns the ignition ON with engine OFF and clears the DTC. The engine is then started. The engine now runs smooth and the scan tool data list shows no misfire counts for cylinders 3 and 4. A test drive is done to verify all is okay before completing the repair paperwork. The customer states the spark plug wires and spark plugs had been changed a year earlier by another repair shop. Since the spark plug wires all appear routed correctly and there are no other misfires, there is no reason to recommend further service. It may be possible that this plug was accidentally overlooked during a previous service and was original to the vehicle. The strategy-based diagnostic process integrates your knowledge, the scan tool data, and service information to a successful vehicle repair.

No DTC-Based Ignition System Diagnosis 5-8 Diagnose ignition system faults without DTCs.

The misfire monitor can set a DTC for a specific cylinder or random misfires, provided the misfire counts are within the parameters to set a DTC. The misfire counts can usually be monitored for each cylinder using the scan tool (FIGURE 5-39). Notice that misfires are being counted but not with enough occurrence to exceed the limit and store a DTC. Even though the misfire count is not high enough to set a DTC, the customer will notice rough running and a lack of power. A faulty crankshaft position sensor or related wiring will cause a no-start, stalling, or rough run condition, but this usually does not set a DTC. Other ignition system faults that may not set a DTC include extended cranking time, rough running engine, lack of power during acceleration, and what can feel like the engine cutting out during steady cruise.

FIGURE 5-39 Misfire counts can usually be monitored using the scan tool. This allows the technician to home in on the cylinder that is causing the issue. © Jones & Bartlett Learning.

Description The technician approaches no-DTC ignition-related concerns using strategy-based diagnostics based on the vehicle symptoms as follows: 1. Verify the customer’s concern. This may require a test drive under the same conditions described by the customer. 2. Research possible faults and gathering information. This includes checking for DTCs, including history and pending. Search the service information for relevant technical service bulletins and

symptom-based diagnosis charts (FIGURE 5-40). Create a list of the possible causes. Place the causes in order of most likely to least likely based on their relationship to the customer concern and what you noticed during your test drive.

FIGURE 5-40 The problem symptoms table in the vehicle service information lists the ignition system as the possible cause of many drivability concerns. © Jones & Bartlett Learning.

Description 3. Conduct focused testing. Without a DTC, the technician must use their knowledge and the symptom-based diagnostics in the service information. The scan tool data list offers misfire counts, even though a DTC is not set. A cylinder or cylinders with some counts showing should probably get your attention first. Also, fuel trim outside of normal range and being too rich or too lean can help guide you. Note that a partial misfire increases oxygen levels in the related banks exhaust, creating a false lean condition. The increase in fuel to compensate on that bank can lead to an overall poor running condition. The goal is to methodically isolate the cause to the cylinder or cylinders with the issue. It may or may not be an ignition issue. It may be a fuel issue, such as an

injector partially clogged, or it could be mechanical (e.g., an exhaust valve where the lash adjustment is too tight and compression is reduced). Once you have determined it is not fuel or a mechanical issue, then begin with the basics. Inspect the coil and spark plug well for water, oil, or carbon track contamination. If okay, perform a spark test. If okay, inspect the spark plug. If there is no spark, follow the service information to diagnose the coil and related circuit. 4. Perform the repair. After isolating the cause of the fault, you make the repair. This may be replacing a spark plug with a small crack in the insulator or repairing a leaking rocker cover gasket that has contaminated the spark plug well, causing ignition voltage to bypass the spark plug electrodes. Care in following the repair procedures, including torqueing of the spark plug and fasteners, ensures that your repair work is done correctly and avoids a comeback situation. 5. Verify the repair. Repeat your initial test drive and note that the symptoms are no longer present. Verify with the scan tool that misfire counts are zeroed for all cylinders and there are no pending DTCs present after returning from the test drive route.

Engine Cranks No-Start Diagnosis After verifying the concern during step 1 of the strategy-based diagnostic process, you must research possible fault diagnostics located in the service information. For the example in FIGURE 5-41, a vehicle has been towed in for a crank no-start condition. Following is the application for using the symptombased diagnostics for this sample vehicle:

FIGURE 5-41 Access the data list to verify sensor operation. © Jones & Bartlett Learning.

Description

Immobilizer system: The vehicle has a smart key and the vehicle cranks when the start button is pressed. There are no immobilizer-related DTCs and no related warning indicators illuminated on the instrument cluster. The scan tool data list for the immobilizer system shows the key is detected. This cause can now be checked off as okay (FIGURE 5-42).

FIGURE 5-42 A crank but no-start condition can be caused by trying to use a nonprogrammed key or a fault in the immobilizer system. © Jones & Bartlett Learning.

PCM 5-V reference: A quick check of the ECT and intake air temperature (IAT) can let you know if the data are accurate. The technician can quickly check for the 5-V sensor signal reference using one of two methods. If the scan tool is already connected to the vehicle, access the PCM data list (PID DATA) for the ECT and IAT readings. Since this is a no-start condition, the temperatures indicated should be very close to ambient (outside) air temperature. Sensor readings very close to ambient temperature indicate reference voltage should be okay. Readings that are not close to ambient temperature require a check of reference voltage. Check for voltage at an easy-to-reach sensor, such as the IAT. There should be very close to 5 V on the signal wire when it is disconnected from the sensor. If it is okay, you can move forward. If not, begin your diagnosis by following the service information for no or incorrect reference voltage present. ECM power source circuit: The PCM (ECM) communicating with the scan tool indicates it has source voltage and ground. Verify that there are no DTCs related to any system, including PCM memory or processor operation. If a DTC is present, follow the related diagnostics for the DTCs. CKP sensor: The CKP sensor signal is required for the PCM to operate the ignition coils and fuel injectors. A no-DTC, crank no-start condition may be related to a CKP fault. The service information in our example vehicle indicates checking the CKP sensor resistance to verify that it is okay or out of range. You can also check the CKP by cranking the engine while monitoring the

PCM data list. The engine speed data are from the CKP, and if it remains at 0 during cranking, there may be a fault in the CKP or related harness wiring. CKP data that during cranking usually appears as an engine speed of 250 to 300 rpm on the scan tool data list. A cranking RPM in this range usually indicates that the CKP is operating normally and the cause of a no-start or no-spark condition is not due to the CKP sensor input. CMP sensor: CMP sensor signals can also affect ignition system operation. These sensors are tested in the same manner as CKP sensors. Monitor CMP sensor data on the scan tool PCM PID data list. CKP sensors are usually MRE-type sensors and output a digital signal with signal gaps to indicate position accurately (FIGURE 5-43).

FIGURE 5-43 Test the CKP according to the service information and document results on the repair order. © Jones & Bartlett Learning.

Connect the DSO as described in Figure 5-44. Note the CMP trigger wheel in this example has three gaps of varying length. These gaps create gaps in the square wave output signal and allow the PCM to process the data to determine camshaft position, and when compared to CKP signal allow the PCM to control variable camshaft advance and retard position. A missing signal, a signal that is too low in output voltage, or one that has an abnormal waveform can cause a no-start condition. Verify that circuit voltages correspond to service information specifications and that there are no voltage drops in the wiring. Replace a faulty CMP sensor or repair a fault in the wiring as required. Valve timing: Valve timing issues can create a no-start condition (FIGURE 5-44). A timing belt or timing chain failure may be the cause. Engine damage may be present due to valve-to-piston clearance issues when the timing belt or chain (or related chain components, such as guides) fail. The crankshaft must be timed to the camshaft(s) correctly or the engine may not start, or if it does

run, there can be rough running issues at certain engine speeds and engine loads. Variable valve timing controls are used to advance or retard the camshafts. The oil pressure-type control valves rarely would cause a no-start condition, as they are not in operation during engine cranking. The electronic type could cause this type of failure though. You can verify camshaft position using the PID data list and monitor camshaft commanded position to actual position. A large discrepancy will require verifying actual camshaft position relative to the crankshaft and variable actuator operation (electric type). Variable camshaft timing phasers on the camshaft gear can fail; however, this usually creates a great deal of engine noise when running. The phasers usually have a lock pin that engages during engine cranking so the cam-to-crank timing is not variable under cranking conditions. For this reason, a cam phaser is usually not the cause of a no-start condition. If you suspect a cam phaser concern, follow the service information inspection procedure. This usually includes removing the valve/rocker cover to inspect the components.

FIGURE 5-44 Camshaft position data are usually displayed on the scan tool. This example shows the intake and exhaust camshaft actual and commanded (specified) positions. © Jones & Bartlett Learning.

Spark test: This may be one of the first tests you choose to do, as it is relatively quick and straightforward. Remove the ignition coil on cylinder 1. Install a spark tester by placing the electrode portion into the coil (or spark plug wire boot) and connecting the tester’s alligator lead to a good ground. Crank the engine and note whether there is spark. If no spark is present and the engine does not start, review the items already covered related to CKP, CMP, and PCM issues. Verify that source voltage is present at the coil with the ignition ON. If no voltage is present, review the related wiring diagram to isolate the cause of no voltage to the ignition coils (FIGURE 5-45).

FIGURE 5-45 Note the varying CMP signal gaps in the red trace indicate camshaft position for the PCM. © Jones & Bartlett Learning.

Description Fuel-related no-start faults: Faults in the fuel pump system and fuel injectors can cause a no-start condition. The diagnostics for these components are covered in Chapter 3 of this text. These tests include checking fuel pressure and verifying injector operation.

Engine Runs Rough, No DTC Diagnosis Case Study The technician has a vehicle in with a rough running condition. A review of the service information identifies many systems that can cause this concern (FIGURE 5-46). Where do new technicians begin? Referring to the basics of engine operation, the technician should check fuel, ignition, and compression to work through determining which system is malfunctioning. Using a scan tool to start the process quickly allows the technician to home in on the area that is malfunctioning. Rather than make an educated guess at this early stage of diagnosis, the technician does the following:

FIGURE 5-46 The DSO connects to the CMP by connecting the positive lead to the positive output signal at the sensor and the negative lead to the negative output at the sensor. © Jones & Bartlett Learning.

1. A scan tool check shows no DTCs present. The technician accesses the misfire data from the Mode 6 menu and notes that there are misfire counts for all cylinders but not enough to set a DTC. The engine is running so the technician can rule out the following: a. No voltage to the ignition coils 2. Conduct a cylinder balance test and note that all cylinders have the same rpm drop during the test. This indicates that each cylinder is contributing equally, so a compression test is not noted, at least not yet. Determining the mechanical integrity of the cylinders allows the technician to eliminate a mechanical fault from the potential causes of the failure. 3. Since the cylinder balance test looks only at the mechanical integrity of the engine, the ignition system must be inspected. The technician removes the coils to inspect the spark plugs. Upon removal, it is noted that the ignition coils are covered in engine oil from failed rocker cover spark plug well seals (FIGURE 5-47). The technician has quickly located the cause of the rough running condition.

FIGURE 5-47 The rocker cover spark plug well oil seal has failed, allowing engine oil into the spark plug well. This can cause a misfire condition. © Jones & Bartlett Learning.

4. The technician replaces the rocker cover gasket and spark plug well seals to correct the oil leaks. It is critical when replacing this gasket and the seals that form-in-place-gasket (FIPG) is used only where specified and that all fasteners are torqued to specification in order. 5. The technician inspects the positive crankcase ventilation (PCV) system to ensure it is operating normally. This includes a check of the PCV valve and related hoses. A clogged PCV valve or lack of correct PCV vacuum due to a collapsed hose can cause an increase in crankcase pressure, causing oil leaks. 6. The technician replaces the ignition coils due to the oil contamination. This contamination allows a path to ground for the high voltage from the secondary coil that bypasses the spark plug electrodes. Over time, this creates a carbon track in the housing of the coil assembly that can allow the high voltage to pass through to ground even after cleaning. This type of voltage “short” to ground can also damage the internal coil components and lead to a full coil failure. Replacing the coil assemblies ensures the rough running condition does not return. New coils are installed, using dielectric grease on the high-tension end to ensure good conductivity and ease of removal in the future (FIGURE 5-48).

FIGURE 5-48 Use dielectric grease in the spark plug boot to ensure good conductivity and for ease of removal during any future service. © Jones & Bartlett Learning.

7. Completing the strategy-based diagnostic process, the technician verifies the repair. Starting the engine now, it is running smoothly at idle. A review of scan tool data shows steady engine rpm and no misfire counts. The lack of a misfire counter rising in the data stream indicates the technician has repaired the cylinder misfire. The next step is for the technician to perform a thorough test drive under various loads and to verify that there are no longer any rough running conditions noted. A final review of scan tool data show that misfire counts are still 0 counts for all cylinders. The technician completes the repair order details and this vehicle is ready for return to the customer. This case study illustrates the integration of service information and technician knowledge for noDTC–based ignition faults. The service information lists many items from a symptom-based diagnostic strategy for a rough running engine. The technician must use their knowledge and experience to determine what component or system to inspect first. As the technician, you will find as you advance through this course that there are additional tools available that when all taken into account allow you to determine quickly which system to focus on. In taking a building block approach to advanced engine performance diagnosis, you will be able to apply this knowledge and gain the experience necessary to take all diagnostic information from the scan tool, service information, and your experience to develop a strategy-based diagnostic plan for each vehicle you work on.

WRAP-UP Ready for Review Ignition system loads run parallel to engine loads, and the PCM adjusts to maintain engine operation. The PCM controls ignition system operation on OBD II vehicles. Using CKP and CMP sensors, the PCM fires the ignition system at the proper moment to maintain engine operation. When inspecting ignition components, start with the wear items: spark plugs, spark plug wires, ignition coils, and ignition coil boots. Serviceable ignition system components will support the ignition process; one failed component will cause the system to fail. A spark tester is a good way to verify the quality of spark the ignition coil is putting out. Inspecting spark plugs should be conducted when the technician suspects an ignition system concern. Looking at the spark plug wires for holes, frays, or other damage will ensure something is not affecting the operation of the spark plug wire. Testing the spark plug wire with an ohmmeter will verify the integrity of capacity of the spark plug wire. Poor inputs from the CKP or CMP can affect the ignition system operation. Verifying the mechanical timing of the engine should be done to make sure the CKP and CMP sensors are reading properly. Base ignition timing is the mechanical timing set of the ignition and camshaft. Advancing or retarding the ignition timing is done to increase speed or increase fuel economy. The knock sensor is used to protect the engine from spark knock. DTCs are used to help the technician diagnose an ignition-related fault. Without DTCs, the technician must go back to the base ignition system to determine which component is at fault.

Key Terms Base ignition timing adjustment The manual setting of initial ignition timing until the PCM advances or retards the ignition timing for engine operation. Camshaft position (CMP) sensor A detection device that signals to the PCM the rotational position of the camshaft. Coil near plug (CNP) A type of ignition system used on late-model vehicles that uses one coil placed near each spark plug with a small spark plug wire attached to the spark plug. Coil on plug (COP) A type of ignition system used on late-model vehicles that uses one coil placed above each spark plug. Crankshaft position (CKP) sensor A sensor used by the PCM to monitor engine speed. It can be one of three types of sensors—Hall effect, magnetic pickup, or optical. Dielectric grease A silicone-based grease that repels moisture and protects electrical connections. Electrode The hottest part of the spark plug and the path of least resistance, it allows the electrical current coming from the coil to get close the ground strap where it arcs to complete the circuit. That arc is what ignites the fuel within the cylinder. Magneto reluctance (MR) sensor A sensor that uses the principle of magnetic induction to create its signal. It is used to measure rotational speed, including wheel speed, machine speed, engine speed, and camshaft and crankshaft position. Magneto resistive/Hall-effect (MRE) sensor A type of wheel speed sensor that uses an effect similar to a Hall-effect sensor to create its signal. Spark knock An erratic form of combustion that occurs when the ignition process is not controlled by the spark plug.

Review Questions 1. All of the following are correct statements for OBD II ignition systems EXCEPT: a. OBD II ignition systems usually have one coil per cylinder. b. OBD II ignition systems use a CKP and CMP sensor. c. OBD II ignition systems have adjustable base ignition timing. d. OBD II ignition systems may have one coil for two or more cylinders. 2. Which sensor is used to determine which cylinder is on the compression stroke? a. CMP b. CKP c. Knock d. Primary ignition 3. The most common methods to verify that a misfire occurs include all of the following EXCEPT: a. monitor engine speed and which cylinder is on the power stroke. b. monitor spark plug temperature. c. monitor coil secondary signal output. d. monitor spark ionization. 4. The knock sensor functions for which of the following? a. To retard ignition timing b. To set a DTC when spark knock is severe c. To send a signal that pre-ignition is occurring d. To advance ignition timing during spark knock occurrence 5. All of the following can cause a cylinder misfire EXCEPT: a. an open CKP sensor circuit. b. a worn spark plug. c. water or oil in the coil well. d. a faulty ignition coil. 6. Random misfires could be caused by which of the following? a. A faulty spark plug causing several cylinders to misfire b. A faulty ignition coil causing three or more cylinders to misfire c. A fuel delivery condition that is affecting several cylinders d. An open primary circuit on the cylinder 4 coil 7. Cold start random misfires may indicate which of the following? a. Intake valve deposits b. A faulty ignition coil on cylinder 1 c. A faulty spark plug d. A CKP sensor fault

Description © Jones & Bartlett Learning

8. A vehicle has a P0302 DTC, misfire, cylinder 2. The service information shown below indicates the misfire could be caused by any of the following EXCEPT: a. a wiring fault. b. a faulty fuel injector. c. a knock sensor. d. a burnt exhaust valve. 9. Which of the following can be performed to check ignition coil operation for a misfire with DTC P0302? a. Use an HEI spark tester to verify that spark is present. b. Disconnect the injector 2 connector to see whether there is a change in engine rpm. c. Perform a compression test on cylinder 2. d. Inspect the spark plug for electrode wear. DTC Number P0300

DTC Condition Several cylinders misfire simultaneously. One of the following conditions is met (two-trip detection logic): Misfire that could damage the three-way catalytic converter Misfire signaling emission deterioration

Issue Location Engine wire harness Connector connection Vacuum hose connection Ignition system Fuel injector assembly Fuel pressure Mass airflow meter subassembly Engine coolant temperature sensor

P0301 P0302 P0303 P0304

Specific cylinder misfires. One of the following conditions is met (two-trip detection logic): Misfire that could damage the three-way catalytic converter Misfire signaling emission deterioration

Compression pressure Valve timing Positive crankcase ventilation Intake system Intake air control valve actuator Engine control module

10. The primary circuit as shown in the diagram (above) for cylinder 1 is turned ON and OFF by which of the following? a. Igniter b. ECM/PCM c. IGF1 d. Spark plug ground

ASE Technician A/Technician B Style Questions 1. Technician A says all OBD II vehicles use coil-on-plug ignition systems. Technician B says some vehicles use a spark plug wire to connect each cylinder’s coil to the related spark plug. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B 2. Technician A says a misfire can cause other monitors not to run. Technician B says a misfire that can damage the catalyst will cause the MIL to flash. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B 3. Technician A says the high compression and lean air-fuel mixtures GDI engines require platinum or iridium electrodes. Technician B says to keep spark plugs in order when removing them because their condition can help in your diagnosis of a misfire or other performance-related concern. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B 4. Refer to the diagram shown below for a 4-cylinder COP ignition system. Technician A says the IGF signal is generated every time there is a spark event. Technician B says there will be four IGF1 signals for each cylinder trigger signal when viewed on an oscilloscope monitoring the IGT and IGF signals at one coil. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B

Description Description © Jones & Bartlett Learning

5. Technician A says it is always okay to swap one coil with another to determine whether the coil is okay or faulty. Technician B states an oil leak into the spark plug well can cause a misfire. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B 6. Technician A says a spark tester can help you determine whether there is spark from the related coil and if the spark is weak or okay. Technician B says the knock sensor may be at fault if there is a weak spark. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B

7. Technician A says that open loop engine operation takes input from the various engine sensors. Technician B states that when in closed loop the vehicle gets better mileage because it is reacting to the changing needs of the engine. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B 8. Refer to the diagram shown on the next page. Technician A says the CKP sensor may be at fault as indicated by the repeating gap in the signal pulses. Technician B says the CKP trigger wheel may be damaged as indicated by the gap in signal pulses. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B

Description Description © Jones & Bartlett Learning

9. Refer to the diagram shown below. Technician A says a rough idle may be caused by an ignition system fault. Technician B says the knock sensor could cause a rough idle concern. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B

© Jones & Bartlett Learning

10. Technician A says spark plugs may require antiseize on the threads during installation. Technician B says most spark plugs require a high torque of over 50 pounds/feet to ensure they do not loosen due to the extreme combustion pressures, vibration, and temperatures they encounter. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B

© Jones & Bartlett Learning.

CHAPTER 6

On-Board Diagnostics II Diagnosis LEARNING OBJECTIVES After studying this chapter, you will be able to: 6-1

Describe the purpose of OBD II.

6-2

Interpret common diagnostic trouble codes (DTCs).

6-3

Perform basic OBD II scan tool functions.

6-4

Describe how OBD II integrates with engine performance diagnosis.

6-5

Use a data link connector (DLC) breakout box.

6-6

Replicate OBD II component or system monitor test drive cycles as part of the strategy-based diagnostic process.

YOU ARE THE AUTOMOTIVE TECHNICIAN A 2016 Nissan Altima is towed into the shop with a crank no-start condition. Which of the following are applicable and in what order as they apply to the diagnostic process? Check for DTCs. Check the battery in the smart key. Check battery voltage. Use the active test to try to start the engine. Review data list input and output values. Look up service information causes for a no-start condition. Review freeze frame data. Check the Mode 6 monitor data. Application of the strategic diagnostic process would lead you toward two possible paths. The first would be based on use of a scan tool to check for any diagnostic trouble codes (DTCs). If one or more DTCs is present, you should follow the related service information diagnostics for the DTC(s). The other path is use of the diagnosis by symptom service information when no DTC is present. This service information provides a list of components and systems that can cause the condition. This chapter focuses on the function and operation of the on-board diagnostic second generation (OBD II) system. Your knowledge of OBD II allows you to integrate information from the scan tool and service information into the strategic diagnostic process.

OBD II Application 6-1 Describe the purpose of OBD II.

Engine control unit (ECU)-controlled systems began to appear on vehicles in the mid-1970s. These vehicles featured computer-controlled spark, carburetors, or electronic fuel injection. These systems were initially used on a manufacturer’s most expensive models due to the cost and lower production numbers required for components. Examples include the Cadillac Seville and Cosworth Vega with fuel injection, the Lincoln Versailles with computer-controlled ignition, the Chrysler Lean Burn system used on several vehicles, and one of the first, the 1968 Volkswagen Type III, used electronic fuel injection. These early systems did not offer built-in (later called on-board) diagnostics. This was also before computers were available for individual use. Even scan tools were a decade away. Diagnostics were primarily based on measuring voltage or resistance values and comparing to reference values supplied in the service information. What was new to technicians at that time was how very small voltage drops, between 50 and 250 mV, could play havoc with how the vehicle would run. It was not common for a technician to use an analog voltmeter (digital multimeters for automotive use were not available yet) though there usually was one available as part of the engine analyzer or on the battery tester. Most technicians were using a test light to verify that voltage was present. You know from your experience with automotive electrical systems that you cannot detect a small voltage drop with a test light. Also, test lights provide a parallel path for current, and some do not have enough internal resistance, allowing higher current levels in the computer circuit you may be testing, which can damage the ECU. This era was difficult for all involved. These new systems were very new to the automotive environment, with rain, snow, high heat, and vibration to challenge their toughness. The buyers were essentially beta testing much of these new components that promised higher fuel mileage and lower exhaust emissions. For technicians, the era of replacing worn ignition parts or rebuilding a carburetor to restore like-new performance was quickly ending. Computer technology got us to the moon and now it was finding its way under the hood of vehicles. Some vehicle manufacturers had been providing computerized engine control systems, which stored DTCs since the 1980s. Early examples of self-diagnostics were very basic. Ford had offered a basic code-based diagnostic system. The technician would use a jumper lead to connect the designated test pins together, and the engine control module (ECM) would cycle the thermactor (smog pump) solenoids. The solenoids basically provided a numeric Morse code. The technician would count three clicks from the first solenoid, then one click from the other for code 31, for example. Shortly after this, Ford offered a handheld tool called a STAR Tester that would flash a lightbulb that you could then use to obtain a code: three flashes, pause, then one flash equals code 31. An analog voltmeter could be used also, just watch the needle sweeps. GM was the first to offer what really became on-board diagnostics (later called OBD I when OBD II began to appear in the mid-1990s). There was an assembly line diagnostic connector under the instrument panel area (sometimes it was in the glove box, the Fiero as an example). The technician could jump two pins together, and the Check Engine or Service Engine Soon light would flash out the codes. Simple as this sounds, it was extremely important for technicians to finally have a clue as to what area of the engine control system had some type of fault. The Check Engine light was noticed by the California Air Resource Board and the Environmental Protection Agency. Basic self-diagnostics were required in California by 1991, although many domestic vehicles used a Check Engine light (Chrysler used a Power Loss light) and use of a scan tool for DTCs. GM began to offer live data that could be viewed in a scan too. Vehicles sold in California were required to provide on-board diagnostics beginning in model year (MY) 1991. This required a way to obtain DTCs with a scan tool and provide access to ECM input and output data. Although this was helpful for technicians working at new vehicle dealers, the independent repair facilities were faced with using

generic scan tools that required adapters to work with each different vehicle make (FIGURE 6-1). Also, additional scan tool software often had to be purchased for the scan tool to communicate with Asian and European vehicles. The lack of a standardized communication protocol, data link connector (DLC) location, and design was difficult for the automotive repair industry but also the manufacturers. A fresh approach was needed to standardize on-board diagnostics.

FIGURE 6-1 Pre-OBD II vehicles require scan tool adapters to connect to the various DLC designs. © Jones & Bartlett Learning.

OBD II came about from several areas that have a strong voice within the automotive industry: Society of Automotive Engineers (SAE) Environmental Protection Agency (EPA) California Air Resource Board (CARB) Select state vehicle pollution regulatory agencies Vehicle manufacturers Developing OBD II required all vehicle manufacturers, SAE, several government agencies, and representatives for the independent repair facilities to agree to the OBD II operating framework. There was also work with International Standards Organization (ISO), which includes European and Asian based manufacturers and engineering groups. The outcome from several years of difficult meetings where all parties could agree were several SAE standards documents for OBD II (FIGURE 6-2).

FIGURE 6-2 The Society of Automotive Engineers published several standards documents, which define almost all aspects of OBD II. © Jones & Bartlett Learning.

Description OBD II was required on vehicles for all 1996 MY vehicles; however, there were some vehicles sold in 1994 and 1995 with the OBD II diagnostic communication link (DCL) in place that featured some OBD II functions (FIGURE 6-3). With the passage of time, there have been designations to OBD II application based on the vehicle model year. Vehicles from 1996 to 1999 are sometimes referred to as early OBD II systems. These vehicles may have some OBD II functions that are not fully implemented or have gone through one or more updates to improve system performance. States with emission testing have had to adapt to these vehicles’ anomalies, with focus on OBD II monitor status not indicating complete or sufficient monitored systems to pass the required emission inspection test.

FIGURE 6-3 The data link connector (DLC) enables the scanner to access data stored in the vehicle’s various computers. © Jones & Bartlett Learning.

Vehicle computer architecture began to change in the late 1990s, with manufacturers linking various system ECUs together to form networks to share data and control of some functions. The Controller Area Network (CAN) protocol was developed to standardize this type of communication for engine, drivetrain, braking, and other vehicle control systems. U.S. and European vehicles began to adopt CAN in the late 1990s, with other manufacturers following throughout the early 2000s. As these vehicles were sold, technicians could usually identify them based on the required use of a CAN adapter added to the scan tool. CAN OBD II was required for scan tool communication for all 2008 and later vehicles. The requirement was only for scan tool communication with the vehicle systems; however, most also used the CAN system for high-speed network data sharing for engine, driveline, braking, and SRS ECUs. The CAN network uses a twisted pair wiring bus to connect each ECU on the network (FIGURE 6-4).

FIGURE 6-4 (A) A pre-CAN DLC is similar to a post-CAN CLD; it is just missing the required CAN data lines. (B) Pin location mandated by OBD II regulations. Any pin marked discretionary is available for use by manufacturers for additional on-vehicle diagnostics. This is a post-CAN DLC. © Jones & Bartlett Learning.

Description CAN signals are based on a no-signal voltage of 2.5 V. One wire transmits the data digital signals that create pulses from that increase to 3.5 V, and the other creates a mirror image as the voltage drops to 1.5 V. This is why the signals are called CAN high and CAN low (FIGURE 6-5). This type of data transmission, along with the twisted pair wiring, has the ability to interpret data even if an outside signal (e.g., from a cell phone) affects the signal. The mirror imaging of the signal allows the ECUs to interpret the data pulses despite the interference. Some manufacturers are using a new network system called Flexray that allows for very high-speed data transmission among groups of ECUs while continuing to use CAN to meet the 2008 requirement for scan tool communication.

FIGURE 6-5 CAN uses twisted pair wiring to transmit signals. © Jones & Bartlett Learning.

OBD I as a required standard existed for about 5 years for all manufacturers. OBD II is now well over 20 years old. The longevity of its use as the diagnostic standard for this long demonstrates how working together and—where needed—making compromises can lead to a very robust method for handling vehicle powertrain diagnostics. There has been mention of OBD III standards, but the team has so far found that building on OBD II is sufficient to meet new technology. TECHNICIAN TIP OBD II is required for pollution-controlled motor vehicles (FIGURE 6-6). There is no current requirement for a manufacturer to include OBD II in electric vehicles (EVs). Tesla does not use OBD II on its vehicles, nor do some pure electric vehicles, such as Nissan Leaf and Chevrolet Bolt. This trend may see a repeat of what happened with OBD I where each manufacturer has proprietary methods for providing diagnostics to the technician.

FIGURE 6-6 The Vehicle Emission Control Information (VECI) label found in the engine compartment shows this vehicle conforms to OBD II California standards. © Jones & Bartlett Learning.

OBD II DTC Structure 6-2 Interpret diagnostic trouble codes (DTCs).

OBD II DTCs are a great leap forward from early OBD systems where each vehicle manufacturer used its own DTC designations. Most OBD II DTC structures use a five-character alphanumeric code to create each DTC (FIGURE 6-7). Your ability to understand the meaning of the characters allows you to focus on a particular input sensor, output device, or emission control system quickly.

FIGURE 6-7 OBD II DTCs use alphanumeric characters. Most DTCs are five characters; some manufacturers now use seven characters. © Jones & Bartlett Learning.

Description The first DTC character is usually a letter that designates the overall vehicle area (FIGURE 6-8):

FIGURE 6-8 OBD II DTCs characters identify the area of the vehicle and other information that can assist your diagnosis of the customer concern. © Jones & Bartlett Learning.

Description B—Body systems: HVAC, SRS, Lighting, Camera Systems, Infotainment C—Chassis systems: ABS, VSC, EPS, Active Suspension P—Powertrain: Engine and Transmission, AWD/4WD U—Vehicle networks: CAN, LIN, MOST, Flexray The second character identifies whether the DTC is a generic code. This means the DTC would have to apply to the same component by all manufacturers using the DTC as part of their engine control software diagnostics. Generic codes are designated by the number 0 or 2 in the second character position. Manufacturer-specific DTCs are designated by a 1 or 3 in the second character position. These DTCs are not the same between manufacturers and allow flexibility for new technology or proprietary systems used by auto companies to create DTCs for them. The third character identifies the powertrain-related system as follows: 0—Crank and camshaft position sensors, HO2S/AF ratio sensor heater 1—Fuel and air metering, ECT, MAF, MAP 2—Fuel and air metering focused on the injector components, feedback operation including HO2S/AF sensors and fuel trim 3—Ignition system and cylinder misfire 4—Auxiliary emission controls, including the catalyst, EGR, and EVAP 5—Vehicle speed control, and idle control and engine timing, inputs related to braking and power steering

6—ECM/PCM output control 7, 8, 9—Transmission, AWD and 4WD A, B, C—Hybrid systems The fourth and fifth characters designate the component and the type of fault. For example, P0111, P0112, and P0113 are all related to the intake air temperature (IAT) sensor. The last two digits focus on the type of fault: 11 is a range or performance problem 12 is voltage low input usually indicating a circuit short 13 is voltage high input usually indicating an open circuit The DTC nomenclature, once understood, allows the technician to focus on the component or system and what type of fault has caused the DTC and is essential to the strategy-based diagnostic process. The DTC immediately focuses your attention on the service information, or if you are already familiar with the diagnosis for this DTC you can move forward with the applicable inspection and test procedures.

Case Study: 1999 Toyota Tacoma A customer has her 1999 Toyota Tacoma in for service because the malfunction indicator lamp (MIL) is illuminated. The vehicle stalls several times when cold and runs rough at idle and lower rpm. It also has a lack of power. The technician connects the scan tool to the DLC and notes DTC P0402 excessive exhaust gas recirculation (EGR) flow and P0300 random misfires. P0402 breaks down as follows: 1. 2. 3. 4.

P = Powertrain 0 indicates a generic DTC 4 indicates the fault is with an auxiliary emission control system 02 is the specific fault, excessive EGR flow detected for this DTC

P0300 breaks down as follows: P = Powertrain 0 indicates a generic DTC 3 indicates an ignition system fault 00 indicates misfires that are occurring in all cylinders Both of these DTCs are generic. That means if a Ford or a Honda had these same DTCs, the definitions would be the same. The Ford or Honda would have excessive EGR flow and random misfires. This applies even though the operation of the EGR system, for example, may be different for Ford, Honda, and Toyota. The technician must determine which DTC to deal with first. A review of both DTCs shows that excessive EGR flow can cause a misfire DTC. The technician begins the diagnostics with the EGR system because that could cause a misfire condition. The EGR temperature sensor is indicating EGR flow at low engine speed based on the parameter ID (PID) data, as the temperature is over 250°F. The technician checks the EGR vacuum source, and vacuum is present at idle. This is not correct. Moving to the EGR vacuum control solenoid, the technician disconnects the harness connector and the engine immediately smooths out. The solenoid is energized when it should be OFF. The ECM supplies ground to the solenoid (Toyota calls it a vacuum switching valve [VSV]). The wiring harness is okay and there is no short to ground on the control circuit wire between the solenoid and the ECM. The ECM output driver has shorted to ground (the transistor has failed shorted) (FIGURE 6-9). The technician replaces both the ECM and the VSV solenoid. This is standard practice when an output driver fails open or shorted. That rarely happens on its own. Usually a failing inductive device, such as a solenoid, begins to fail; this can increase the current load in the circuit if the windings begin to short together and internal resistance is reduced. The technician clears the DTCs and performs the EGR drive cycle to run the monitor. A review of the scan tool data shows no DTCs, and the EGR monitor is complete and passed.

FIGURE 6-9 The ECM often controls the ground circuit for output devices, such as the idle air control valve and EGR vacuum switching valve. Toyota.

Description

OBD II Scan Tool Modes 6-3 Perform basic OBD II scan tool functions.

OBD II was mandated for use for automobile manufacturers. This is not to say that automakers did not have input into the process. The SAE, ISO, EPA, CARB, and auto manufacturers all worked together to develop OBD II. The EPA provided the overall goals (e.g., use of a standardized DLC), and SAE—with automaker input—developed the various standards that define the implementation of OBD II. These standards are published for the industry, including manufacturers, state agencies, the EPA, scan tool manufacturers, and others to ensure that a vehicle or a scan tool meets the standards. These standards often are designated with a letter and set of numbers. SAE J1979 is the paper that communicates to auto and scan tool manufacturers the OBD II scan tool operating modes. SAE J1979 has been revised to keep up with industry advances and currently defines the scan tool modes. The symbol that looks similar to a dollar sign actually indicates a hexadecimal format for displaying data. Hexadecimal is a base 16 method of counting. We have grown up with counting on a base 10 method. If you start at 0 and count up, when you get to 9, that is the tenth digit and you start over by adding a 1 in front of the next number, a zero in this case, to create the number 10. Hexadecimal is based on a byte of information having 8 bits, so in effect the engineers are using two bytes, or 16 bits, of data that are compressed. The table shows that a 0 and a 1 are the same in binary code, decimal (how we write numbers) and hexadecimal (FIGURE 6-10).

FIGURE 6-10 Hexadecimal format allows the ECU to compress data for increased storage and processing speed. © Jones & Bartlett Learning.

Description Remember from electronics that ECUs process data made up of zeros and ones. The hexadecimal nomenclature can compress all the zeros and ones, allowing for more data to be processed and stored. The good news is that with CAN OBD II, required for MY 2008 and later vehicles, and used by some manufacturers before that date, most scan tools do a very good job of converting the hexadecimal data into data that you can use right off the scan tool display. Early OBD data often had some hexadecimal data that appeared on the scan tool screen, especially when accessing monitor test result data. The data must be converted for you to use during your diagnosis (FIGURE 6-11). TID is the test ID number, and CID is the component ID number. You use the TID and CID to decipher the test results listed under the Test column of data on the scan tool display. As stated, the vehicles that use this format are 11 to 20 years old or older now, so this is not something you encounter with every vehicle in your shop stall.

FIGURE 6-11 Hexadecimal data were common on early OBD II scan tool monitor test result displays. The technician would use service information to decode the information as part of diagnosis. © Jones & Bartlett Learning.

Be familiar with hexadecimal so that if you should encounter it on the scan tool display you know what it is and that the service information will provide the conversion data you need for your diagnosis. The example in FIGURE 6-12 shows a Ford EGR system DPFE sensor data. The scan tool displays TID $41 and CID $11, and the service information defines the test and the test result unit value. In this case, the pressure is measured using inches of water pressure. The conversion process for the test result is also shown:

FIGURE 6-12 An example of hexadecimal scan tool data. © Jones & Bartlett Learning.

Description Test result of 31,433 is positive. Multiply by 0.0078: 31,433 × 0.00078 = 245.18 in H2O. Inches of water converted to PSI equals 8.86 psi. Converting the TID, CID, and the data now provides a basis to move forward with diagnosis for these early OBD II vehicles. TECHNICIAN TIP General scan tool mode often displays data with hexadecimals. This mode may be required when using a manufacturer’s scan tool on a different manufacturer’s vehicle or to perform a specific diagnostic test on the vehicle.

The scan tool modes are shown in FIGURE 6-13. Most scan tool menus just show these in an easyto-select function list. Mode 1 is often shown as descriptive text, and it may or may not use a hexadecimal mode ID (TABLE 6-1).

FIGURE 6-13 Scan tool main menus list the available OBD II modes and may offer non–OBD II menu items. © Jones & Bartlett Learning.

TABLE 6-1 Scan Tool Modes Define the Primary Scan Tool Functions That Interface with the Drivetrain ECUs Diagnostic Service Mode of Operation

Description

Standard

$01

Request current powertrain diagnostic data

SAE, ISO

$02

Request powertrain freeze frame data

SAE, ISO

$03

Request emission-related diagnostic trouble codes

SAE, ISO

$04

Clear/reset emission-related diagnostic information

SAE, ISO

$05

Request oxygen sensor monitoring test results

SAE, ISO

$06

Request on-board monitoring test results for specific monitored systems

SAE, ISO

$07

Request emission-related DTCs detected during current or last completed driving cycle

SAE, ISO

$08

Request control of on-board system, test, or component

SAE, ISO

$09

Request vehicle information

SAE, ISO

$0A

Request emission-related DTCs with permanent status

SAE

OBD II Mode 1 Data Display OBD II scan tool Mode 1 displays sensor input, actuator output, and powertrain control module (PCM) data for fuel trim and usually misfire counts. The data default is usually alphanumeric, displaying data that are processed by the PCM. For example, the engine coolant temperature sensor is a voltage signal

to the PCM. This voltage is then compared to a look-up table, where a voltage is then assigned a temperature equivalent. The scan tool displays the engine coolant temperature (ECT) data (FIGURE 614). It is critical to note that a circuit fault that sets a DTC can result in a fail-safe value being used to substitute for the missing data. Some circuit or component faults do not code. Excessive resistance in the ECT signal wiring can cause the measured voltage to be lower than what it should be under normal conditions. The scan tool will then display a temperature reading that is lower than what is actually occurring. Small differences may be difficult to detect; however, an engine that is at normal operating temperature and the scan tool ECT PID showing 163° F should alert you that there may be an issue in the ECT circuit.

FIGURE 6-14 The scan tool Mode 1 displays input and output data. There may also be data for misfire counts and fuel trim displayed in this mode. © Jones & Bartlett Learning.

The Mode 1 data may also be displayed in graph format. The graph can help you determine whether there is an intermittent open by looking for extreme data changes when you wiggle a harness or connector (FIGURE 6-15). It can also be used to compare one data PID with another (e.g., the B1S1 airfuel ratio sensor with the B1S2 oxygen sensor) or the throttle position data with the accelerator pedal position data. It is important to note that the graph is based on the PCM processed data. It does not take the place of using a digital storage oscilloscope (DSO) to observe input or output signals that may be required to verify system or component operation.

FIGURE 6-15 The scan tool may be able to display sensor data in graph format to assist your diagnosis. © Jones & Bartlett Learning.

OBD II Mode 2 Freeze Frame Data OBD II requires that when a DTC sets, the ECM/PCM store a data snapshot called a freeze frame (FIGURE 6-16). The data are very useful for you during the diagnostic process. From the data, you can see how fast the vehicle was traveling, engine load, engine temperature, engine rpm, fuel trim values, and more. The data can help you duplicate the condition in case the fault is intermittent, and you can ensure your repair fixed the problem by doing a test drive that is similar to these conditions.

FIGURE 6-16 OBD II requires a freeze frame of data stores when a DTC sets. © Jones & Bartlett Learning.

TECHNICIAN TIP Clearing DTCs on most vehicles will also erase the freeze frame data. Be sure to capture this data by saving it, if that is an option on your scan tool, or you can take a photo of the scan tool screen with your smartphone. The data can be a critical diagnostic tool, especially for a DTC that sets, but then becomes a history DTC because the fault is intermittent. Testing without reviewing the freeze frame could result in a no trouble found diagnostic result with the vehicle in your shop stall. Reviewing the vehicle speed, engine temperature, and other conditions when the DTC set could help you duplicate the condition. Your diagnosis can then be more focused on factors such as a bad pin in a connector or some other factor causing the condition, and through use of the strategy-based diagnostic process you could correct the fault and prevent a MIL ON comeback situation.

OBD II Mode 3 Diagnostic Trouble Codes DTCs are displayed on scan tools using OBD II Mode 3 (FIGURE 6-17). The DTC alphanumeric code and definition are displayed along with the DTC status. Engine and transmission related DTCs begin with the letter P. The numeric elements identify the engine control area and related fault. The scan tool displays a DTC definition, which describes what the PCM detected as a fault. The DTC status is also displayed and can be one or more of the following:

FIGURE 6-17 The scan tool communicates through the DLC with the PCM to display DTCs and their definition. © Jones & Bartlett Learning.

Pending DTC Current DTC History (not current) DTC Permanent DTC

Monitors, Enable Criteria, and the Drive Cycle Pre-OBD II vehicles used engine control software programming that almost exclusively set and stored DTCs when a component-related circuit had an open or a short or the value was extremely irrational for current conditions. As computer hardware and software programming capabilities have expanded since the 1980s, it has become possible for the PCM and related software programming to monitor components and also systems, like the catalyst, exhaust gas recirculation, and variable valve lift or timing control. The term monitor is used to describe the method used by the PCM to determine when a component or system is checked for operation and valid data. Some monitors are continuous. This means that as soon as the ignition is turned on, a component or system’s data is being reviewed by the PCM for faults and rationality. Continuous monitors include the component monitor, which covers almost all sensor inputs and some output devices, like coil-on-plug ignition coils, which provide a signal to the PCM that a coil induction event occurred. For example, the engine coolant temperature is monitored as soon as the ignition is turned ON. The only requirement for the PCM to monitor the ECT is if a DTC has set for the ECT sensor circuit. As long as no ECT-related DTC is present, the PCM can monitor the rationality and functionality of the ECT circuit. If a DTC is set, the PCM usually substitutes a fail-safe value to allow the engine to run as close to normal as possible. Some components and systems are monitored only when specific conditions are met. These are

called non-continuous monitors. The catalyst is an example of a non-continuous monitor. These monitors are structured around specific conditions referred to as monitor enable criteria. The catalyst cannot be monitored as soon as the ignition is turned on. Monitor enable criteria for the catalyst must be met and includes the following: The catalyst must be at normal operating temperature. No DTCs are present for a component or system that could affect catalyst operation. Ambient (outside) temperature is within a specific range. The vehicle must follow a drive pattern that allows for a valid test of catalyst performance, called a drive cycle. The enable criteria can usually be found in the DTC diagnostics service information for the component or system. The drive cycle is often located within the DTC diagnostics. The drive cycle may be as simple as the engine must be running for a set period of time, no matter the vehicle speed or ambient temperature. Other drive cycles, like the catalyst, require the vehicle to be driven a certain amount of time to ensure the catalyst is at operating temperature. Once this enable criteria of the drive cycle is met, the vehicle must then be driven within a fairly steady speed range for a certain amount of time for the catalyst monitor to run and complete. The engine performance diagnostic technician usually performs the drive cycle to run the monitor test. This collects test result data that can help determine the current condition of the system or component and how to proceed with further testing and inspection. It is also important to perform the drive cycle to run the monitor test after repairs to ensure the repair has corrected the condition.

Pending Diagnostic Trouble Codes Pending DTCs occur on the first trip or drive cycle of a two-trip DTC. The PCM monitors the component or system when enable criteria and drive cycle conditions are met. The PCM determines whether the component or system is operating within or outside of normal limits (FIGURE 6-18). A pending DTC stores when the test result data exceed normal limits. There are no freeze frame data stored with a pending DTC. The next trip where the enable and drive cycle conditions are met and the component or system fails changes the DTC from pending to current and turns the MIL ON.

FIGURE 6-18 Pending DTCs are identified by name or as part of the DTC table on the scan tool. © Jones & Bartlett Learning.

Most two-trip DTCs do not illuminate the MIL for a pending DTC. This is an important operating characteristic of OBD II. A vehicle in for a drivability concern without the MIL ON as part of the concern does not mean that there are no DTCs. There may be one or more pending DTCs present that can provide a diagnostic path for the technician to follow. TECHNICIAN TIP Two-trip DTCs usually require two consecutive trips to set a current DTC and illuminate the MIL. Consecutive trips are complex. For example, a drive cycle that meets the enable criteria and drive pattern for a particular DTC may require steady speed driving of 55 mph for several minutes. A customer who drives 30 highway miles to work will most likely meet this criteria during that trip. However, a lunch trip on surface streets that is 5 minutes will most likely not meet the criteria during that trip. Since this trip did not meet enable criteria, it is not considered a trip for this pending DTC. On the way home, if there is a great deal of traffic and a steady cruise of 55 mph for several minutes does not occur, then this is not a consecutive trip either. If the next morning, the customer is able to have a 30-minute highway drive with several minutes at 55 mph or higher, then this is the consecutive trip that applies, as now the PCM can monitor the component or system again, and if the data are outside normal limits during this trip, the DTC changes from pending to current and the MIL will turn ON.

Current DTCs A current DTC indicates that the fault is occurring right now or has set for the most recent applicable enable conditions and related drive cycle. One-trip DTCs store a current DTC and freeze frame

immediately when the system or component data are out of normal range by the PCM (FIGURE 6-19). A current DTC has the MIL ON except for a small number of manufacturer-specific DTCs that do not illuminate the MIL. For a two-trip DTC, the pending DTC changes to a current DTC when the related enable criteria and drive cycle are met and the fault is detected on the second consecutive trip. A freeze frame stores on the second consecutive trip and the MIL turns ON. A current DTC is where the technician usually begins the inspection and testing using the service information DTC diagnostics.

FIGURE 6-19 Current DTCs indicate that fault is present now or within the previous three drive cycles. © Jones & Bartlett Learning.

History Diagnostic Trouble Codes A history DTC occurs when a current DTC has passed its related test results, and the data have been within normal limits for three consecutive drive cycles (FIGURE 6-20). The MIL turns OFF and the scan tool displays the DTC as a history type. It is important to note that on the first and second consecutive trips, the current DTC status remains and the MIL is ON even though the fault is no longer present. History DTCs remain for a total of 40 trips (the related enable criteria and enable conditions are met), although fuel trim and misfire related DTCs require 80 trips before they self-erase. History DTCs are important for the technician. They provide a window into which component or system the PCM data recently indicated had a fault present. A history DTC can be very helpful for an intermittent condition diagnosis. The fault has not been present for 4 to 39 trips; however, it was present and provides a possible starting point if the fault is related to the customer’s concern that a drivability issue, like a stumble or surge, occurs, but not all the time.

FIGURE 6-20 A current DTC becomes a history DTC after three consecutive drive cycles or trips and the data are within normal limits. © Jones & Bartlett Learning.

Permanent Diagnostic Trouble Codes Permanent DTCs were created in the late 2000s to deal with a customer attempting to turn OFF the MIL before having the vehicle subjected to a smog/inspection and maintenance (I/M) test. Customers would use an inexpensive code reader or even their smartphone and a DLC adapter to clear DTCs and turn the MIL OFF. Most states require a vehicle with the MIL ON to fail the smog or I/M test, even if tail pipe emissions are within normal limits. A failed component or system can raise overall emission levels, and they may exceed limits greatly under conditions that the I/M testing do not duplicate. Permanent DTCs self-erase after three consecutive drive cycles or trips if the related data are within normal limits and there has been no attempt to erase DTCs (FIGURE 6-21). Permanent DTCs erase after one trip if DTCs have been erased using the scan tool and the related fault is no longer detected when enable criteria and the drive cycle are complete. The vehicle is ready for an I/M smog test once permanent DTCs are no longer present.

FIGURE 6-21 Permanent DTCs have been created to prevent a customer from attempting to erase DTCs before having an inspection and maintenance smog test performed. © Jones & Bartlett Learning.

OBD II Mode 4 Clear DTCs OBD II Mode 4 allows the scan tool to clear DTCs from the PCM random access memory (RAM). Erasing a DTC also does the following: Turns the MIL OFF Erases the related freeze frame data Usually resets noncontinuous monitor status to incomplete/not ready Usually erases continuous monitor test result data Is not able to clear permanent DTCs May reset long-term fuel trim learned values to the base fuel map data (0% adjustment) TECHNICIAN TIP Service information often directs the technician to clear DTCs in the very early stages of a MIL ON diagnosis. Before clearing DTCs, the technician should save freeze frame data and review the noncontinuous monitor status (complete or incomplete/ready or not ready) and the related noncontinuous monitor test results. All of this data may be erased when clearing DTCs, and this information may be very useful during diagnosis. For example, the freeze frame contains information on vehicle speed, engine rpm, engine temperature, engine load, and much more. The noncontinuous monitor test result data can assist in diagnosis (e.g., the air-fuel ratio sensor test results may have a ready or pass result but the data may show that the sensor test results are very close to the fail limit). All of the data help the technician begin to focus on what may be the fault cause and where to perform focused testing.

Clearing DTCs may be done as part of the DTC diagnostics when the technician is trying to determine whether the fault is occurring right now (FIGURE 6-22). It is done after the repair is complete to turn the MIL OFF, erase the freeze frame data, and clear noncontinuous monitor status and test results.

FIGURE 6-22 The scan tool is able to clear DTCs by erasing them from the PCM random access memory. © Jones & Bartlett Learning.

OBD II Modes 5, 6, and 7 Monitor Test Results The PCM runs monitor tests as part of OBD II function and operation. There are two types of monitors: continuous and noncontinuous. Continuous monitors run at all times the ignition is ON and, if required, when the engine is running (FIGURE 6-23). These include the following areas:

FIGURE 6-23 Modes 5, 6, and 7 are usually displayed on one scan tool screen accessed through Monitor Test Results from the scan tool main menu. © Jones & Bartlett Learning.

Component monitor Misfire monitor Fuel system monitor The component monitor includes all sensor inputs and related output components except those that are part of the noncontinuous monitor, such as the oxygen or air-fuel ratio sensors. The misfire monitor operates at all times when the engine is running. The fuel system monitor displays fuel adjustments that deviate from the programmed fuel data map, usually in a percentage that is positive (adding fuel) or negative (decreasing fuel) that relates to injector on-time increase or decrease. Continuous monitor data are usually displayed as part of scan tool Mode 1 data list. Noncontinuous monitors run only when enable conditions are met and when related drive cycle completes, and they include the following: Oxygen sensor/air-fuel ratio sensor heater Oxygen sensor/air-fuel ratio sensor Catalyst (usually the primary but not the secondary) EGR Secondary air Evaporative emission system (EVAP) There are two monitors that are listed but generally do not apply to any vehicle. The A/C monitor was specific to vehicles that used R-12 refrigerant to monitor for a refrigerant leak. Heated catalysts were initially thought a viable option when OBD II was developed, but very few vehicles offered this technology (a limited number of Volvos, for example). The industry quickly converted to R-134a refrigerant (and is now converting to a less CO2-intrusive refrigerant, RY-1234) in the mid-1990s and through the use of fuel

control and improved catalyst design, there was no need to use expensive heated catalyst technology. Mode 5, 6, and 7 data offer information that indicates monitor status. This relates to whether the monitor enable criteria was met and the related drive cycle completed. If yes, the monitor indicates complete or ready. If it has not, it indicates incomplete or not ready. A monitor that is complete or ready has test result data stored. You can usually select the monitor from the scan tool screen to view the test result data. Vehicles after MY 2008 usually offer hexadecimal conversion through the factory scan tool to view monitor test results. Some aftermarket scan tools also offer this. The conversion allows the technician to read the test results right from the scan tool display. Hexadecimal results are displayed with what looks like a dollar sign ($) and a number. This requires use of the service information to identify the related component name and the related test identification. You may also have to convert the test results into usable information (e.g., a number is provided and the service information includes a basic math formula, such as a multiplication factor, to then convert the data to a usable result, such as misfires per 200 revolutions or inches of water for an EVAP leak test pressure reading).

OBD II Mode 8 Functional Tests The scan tool offers bidirectional communication, which allows the technician to operate some of the output actuators. This can verify whether a component and the related wiring are functioning. For example, a no-start condition could be caused by a worn fuel pump. The scan tool allows you to attempt to operate the fuel pump (FIGURE 6-24). With a fuel pressure gauge connected to the fuel line, you can use the scan tool to turn ON the fuel pump and verify whether the fuel pressure is within specifications. The service information provides a list of applicable tests that can be performed with the scan tool and what is required to perform the test, including whether the engine must be running or key ON engine OFF (KOEO) (FIGURE 6-25). For some items, such as the purge valve, it is set to a value of 30% duty cycle. You can use your digital multimeter (DMM) or a DSO to view the signal and verify that it is at 30% as well as verifying that the purge valve is operating.

FIGURE 6-24 The scan tool can operate output actuators or vary fuel delivery to verify component operation.

© Jones & Bartlett Learning.

FIGURE 6-25 The service information provides a list of active tests that can be performed on the vehicle. © Jones & Bartlett Learning.

Description The active test is a valuable tool used during diagnostic testing. It can isolate a fault in the component or related circuit, and it can also verify that a replacement part is now functioning and has corrected the fault condition.

OBD II Mode 9 Vehicle Information Scan tool Mode 9 provides access to display the vehicle identification number (VIN) and, for some vehicles, PCM calibration and software version data (FIGURE 6-26). These data can help verify that the correct PCM is installed in the vehicle and whether the related software is correct or requires an update to correct a software code error that can cause a drivability concern (FIGURE 6-27).

FIGURE 6-26 The scan tool Mode 9 displays the vehicle VIN and, for some vehicles, the PCM hardware and software calibration data. © Jones & Bartlett Learning.

Description

FIGURE 6-27 The scan tool can function as a PCM software update tool. This is usually done by the master diagnostic technician to ensure that all processes are followed correctly. © Jones & Bartlett Learning.

A software update is usually outlined in a technical service bulletin (TSB), and the bulletin usually has the technician verify the software version currently stored in the PCM. A software update is done using the scan tool along with an Internet connection (FIGURE 6-28). The software is downloaded to the scan tool. The scan tool then commands the PCM to erase the stored software, and then the new software is uploaded into the PCM. This usually takes several minutes to an hour or so and requires that the PCM remain powered ON and that battery voltage is stable at full charge, requiring the use of a smart battery charger that maintains current and voltage at acceptable levels. Failure to follow a software update procedure can damage the PCM and render it useless. For this reason, most manufacturers allow only the master diagnostic technician to perform PCM software updates.

FIGURE 6-28 Manufacturer and some aftermarket scan tools are able to perform PCM software updates by erasing the current program and uploading a new one. © Jones & Bartlett Learning.

OBD II Advanced Scan Tool Functions Many manufacturer scan tools, and some aftermarket scan tools, provide advanced functions to help you isolate the cause of OBD II system faults. Examples of these include the following: Check mode Evaporative monitor test Check mode allows the technician to narrow the ECM/PCM software malfunction thresholds (FIGURE 6-29). This can include reducing the amount of time that is required before a DTC stores or narrowing the data value range that is used to determine whether the input or output is functioning abnormally. This can help isolate the cause of an intermittent fault that does not set a DTC under your normal test conditions.

FIGURE 6-29 Check mode may be available for some vehicles and scan tools and can help duplicate an intermittent condition. © Snap-on Incorporated.

Almost all scan tools allow the technician to perform the EVAP monitor test on-demand in the shop stall (FIGURE 6-30). The EVAP monitor requires that very specific criteria are met. The scan tool function to run this monitor is a valuable time saver to determine the current condition of the EVAP system and for verifying all is okay after your repairs. To connect the scan tool to the vehicle and perform scan tool Mode 1, 2, 3, and 4 functions for the assigned vehicle, follow the steps in SKILL DRILL 6-1.

FIGURE 6-30 Most scan tools offer a function to run the EVAP monitor to verify system leak status. © Jones & Bartlett Learning.

SKILL DRILL 6-1 Using the OBD II Scan Tool

1. Obtain a scan tool and assigned vehicle from your instructor. Connect the scan tool to the DLC and turn the key ON, engine OFF. Enter the vehicle information as required and select communication with the PCM. Note that menus will vary among scan tool models and manufacturers.

2. Check for DTCs. From the scan tool main menu, select Mode 3 display PCM DTCs. If no DTCs are present, locate the intake air temperature sensor and disconnect the harness connector. A current DTC should have set for the IAT sensor.

3. Access freeze frame. Some scan tools allow access to the freeze frame from the DTC display. Others require that you return to the main menu and select Mode 2, Freeze Frame. Open the freeze frame data. Some PCMs store only one freeze frame, whereas others may store several. The freeze frame helps you determine conditions present when the DTC stored. These include engine rpm, coolant temperature, engine load, vehicle speed, and more. For the IAT DTC you created, you would note that the engine rpm was 0, there was no engine load, and vehicle speed was 0 mph. You will also see the IAT data for when the DTC stored. Use these data to duplicate the conditions if needed as part fault diagnosis and to verify that you corrected the fault, by driving the vehicle in a similar way, after repairs have been made.

4. Access Mode 1 data list: Return to the PCM main menu and then select Mode 1, Data List. The scan tool will display sensor input data as processed by the PCM and output state condition (usually ON or OFF, duty cycle percentage or injector on-time in milliseconds). When using data list, look out for items that are out of normal range, even if they have not set a DTC. Note that the IAT is showing a very low temperature since it is disconnected. Also, the data are based only on what the PCM measures from the sensor, in the form of a voltage or current signal. It takes only a small voltage drop of 50 mV or more to start to cause the voltage signals to be inaccurate. A voltage drop on a signal ground of 500 mV can create all kinds of customer concerns yet may not store any DTCs. The data list can help you isolate this by noting that many of the sensor inputs that rely on a common ground point appear slightly out of range. This is why it is good practice to capture data. You can then compare known good data with data you are currently observing. The service information may also offer data points that you can compare with the scan tool data list to verify data accuracy. It is also good practice to check the voltage drop of the sensor ground points. Voltage drops higher than 50 mV can cause issues.

5. Clear DTCs: Reconnect the IAT sensor connector. Select scan tool Mode 4, clear DTCs. Clear the DTCs. Some scan tools automatically recheck for DTCs. If yours does not, select Mode 3 again to view DTCs. There may be a permanent DTC for the IAT sensor. Remember that this will self-erase after the drive cycle completes on one trip, since we have cleared DTCs.

6. This completes this skill drill. Turn the vehicle ignition OFF. Disconnect the scan tool from the DLC and turn the scan tool OFF. Return the scan tool to its storage location, which usually includes plugging it into its charging cord or charging dock. Return vehicle keys and any other tools to their storage location. © Jones & Bartlett Learning

Role of OBD II in Diagnosis 6-4 Describe how OBD II integrates with engine performance diagnosis.

OBD II functions to provide a mostly standardized set of protocols and use of the same DLC among vehicle manufacturers. As discussed, the SAE, CARB, and vehicle manufacturers worked together to create OBD II. Primary functions include: Standardize emission and OBD-related labeling (FIGURE 6-31)

FIGURE 6-31 Underhood emission labels are part of OBD II and provide the vehicle model year (MY), emission certification level, and emission equipment present on the vehicle. © Jones & Bartlett Learning.

Standardize DLC design and designate pin functions Designate where the DLC can be located on the vehicle Standardize DTCs using an alphanumeric system Add system monitors Store freeze frame data Standardize component and system nomenclature Store system test result data Designate mode functions Illuminate the MIL when emissions exceed 1.5 times the Federal Test Procedure standard

The primary goal of the manufacturers and government agencies was to create an on-board diagnostic system that eliminated adapter cables for the DLC and provided a variety of features that made engine performance diagnosis easier for technicians, especially those working in independent repair shops. The DLC is now the same on OBD II–regulated vehicles and is located near the steering column for easy access (FIGURE 6-32).

FIGURE 6-32 The OBD II DLC is located within 12″ on either side of the steering column for most vehicles. © Jones & Bartlett Learning.

OBD II standardized the trouble codes so the same DTC is used for the same fault for common components, such as the ECT sensor, on different manufacturers’ vehicles. A freeze frame stores for most DTCs to provide other engine performance data at the moment a DTC sets. Most common component and system names are also standardized, reducing the amount of research time needed just to determine which components are related to DTC or during symptom-based diagnostics. OBD II also monitors more than just input sensors, as output operation and system operation are also monitored. The monitors include input and output components for the engine and driveline, cylinder misfires, fuel map adjustments, and emission control system operation. The primary goal is to alert the customer that their vehicle has a fault that is hindering overall performance, which includes power, fuel economy, and emission output, even though in some cases the vehicle seems to run fine.

Case Study: 2008 Chevrolet Tahoe The customer’s vehicle has a check engine (MIL) ON DTC that has been present for several months. The vehicle runs normally and there has been no degradation in performance nor fuel economy. The only

reason the customer sought service is that the vehicle cannot be emission tested with the MIL illuminated. The technician connects the scan tool and obtains DTC P0456 for the evaporative emission system, small leak detected. The technician follows the service information diagnostics for this DTC and isolates the cause to a damaged fuel vapor hose between the fuel tank and the fuel vapor storage canister. Once repaired, the technician tests the system for leaks, and it is okay. DTCs are cleared. The technician drives the vehicle following the overall monitor test drive pattern. This prepares the vehicle for emission testing, as the monitor tests need to be complete (some locations may allow one monitor to be incomplete). The technician verifies the EVAP test monitor is complete and passed. The vehicle is ready to return to the customer. This case study demonstrates the advanced features of OBD II. The vehicle ran fine, and without monitoring the EVAP system for leaks, fuel vapors can leak into the air, adding to the hydrocarbon load that creates smog, especially in densely populated areas. An OBD I vehicle would be unlikely to catch this fault (some very late OBD I vehicles offered some system monitoring, but not EVAP leaks). Even though it was running normally, the emission level performance was out of specification. Keeping all systems functioning as designed ensures that overall performance, even the type that cannot be seen or felt by the customer, is within normal limits.

Testing at the DLC 6-5 Use a data link connector (DLC) breakout box.

The OBD II 16 pin DLC is used on all vehicles since 1996 (FIGURE 6-33). The J1962 type A DLC is for 12-V electrical systems. The type B DLC is for 24-V electrical systems found in some heavy-duty vehicles (e.g., large semitrucks). The DLC must be located within 2 feet on either side of the steering wheel. While it may seem like common sense to use the same DLC and general location among different vehicle manufacturers, it did not start out that way, with all sorts of DLC designs and locations used in pre-OBD II vehicles.

FIGURE 6-33 The 16-pin DLC is standardized among OBD II vehicles no matter the manufacturer. © Jones & Bartlett Learning.

Description TECHNICIAN TIP

Zero-emission vehicles that do not have an internal combustion engine are not required to use OBD II. Most electric and fuel cell vehicles sold by manufacturers that also sell gasoline- or diesel-powered vehicles have continued the use of the OBD II DLC to maintain the ability of their scan tool to communicate with the vehicle (FIGURE 6-34). Tesla vehicles do not have an OBD II DLC nor do they use software that can be accessed with an OBD II scan tool.

FIGURE 6-34 This diagram is an example of how a manufacturer uses the DLC to connect various systems, power, and ground for scan tool communication with the vehicle. © Jones & Bartlett Learning.

Description

The OBD II DLC has pin locations designated for use for all OBD II vehicles as follows: 1. 2. 3. 4. 5. 6. 7.

Manufacturer discretion Bus positive Ford and FCA have used this pin for their own communication protocol Chassis ground Signal ground CAN high K line

8. 9. 10. 11. 12. 13. 14. 15. 16.

Manufacturer discretion Manufacturer discretion Bus negative Ford and FCA have used this pin for their own communication protocol Manufacturer discretion Manufacturer discretion CAN low L line Battery positive (source voltage)

DLC pins 1, 3, 8, 9, 11, 12, and 13 can be used by the manufacturer for proprietary system access that may not be found on other vehicle types. For example, Ford uses pins 3 and 11 for a communication protocol found on vehicles in other countries. Chrysler uses these same pins for its own Chrysler Collision Detection data communication system, which is used on some of their vehicles to share data between ECUs using different protocols than the CAN network uses in many vehicles. The Chrysler scan tool can access data from the vehicle using these pins of the DLC. Pins 5 and 10 are for the SAE J1850 variable pulse width modulation communication protocol used on some vehicles. The Bus + signal uses 0 V as data idle (no message at this time) and the Bus – uses approximately 7 V for data idle. The message pulses are close to 7 V and can be up to 12 bytes (pulses) long. The conversion from a 0 to a 1 in binary code occurs at 3.5 V, allowing for some error correction. Ford and GM use J1850 protocol on some of their vehicles. Pin 4 is connected to chassis ground, which is connected to the battery negative post. Pin 5 connects to a ground distribution point that is used by the PCM and possibly other ECUs on the vehicle. Pin 16 is a 12-V (or 24-V on the B-type connector) source for the scan tool. This pin is usually fused through the power outlet fuse. A blown fuse can lead to a no-scan tool communication fault. Check the related wiring diagram to identify the fuse and verify that it is okay should this fault occur. Pins 6 and 14 are for CAN bus communication with the scan tool. CAN communication is the required protocol for all MY 2008 and newer vehicles. Pre-2008 vehicles may use CAN, the J1850 bus lines (one or both), the K or L lines, or one or more of the proprietary pins for a dedicated network. Pin 7 is the K line, which provides a backup communication with some vehicle systems, usually including the powertrain ECM in case there is a CAN bus fault (FIGURE 6-35). This K line may also be used when using a manufacturer scan tool in generic scan tool mode to access data that may not be available otherwise. Using generic scan tool mode was more common on vehicles prior to MY 2008 that did not have CAN OBD II communication (FIGURE 6-36). The K line also allows most any scan tool to obtain DTCs and some monitor data from most vehicles with an OBD II DLC using the generic scan tool mode.

FIGURE 6-35 Pins 7 and 15 on the DLC offer scan tool communication with the PCM if the CAN bus is not functioning. The communication will be slower, but it will still be possible to obtain DTCs and some other scan tool functions. © Jones & Bartlett Learning.

FIGURE 6-36 Generic Scan Tool mode allows almost any OBD II scan tool to communicate with OBD II vehicles, although the communication speed is usually slower. © Jones & Bartlett Learning.

Description Pin 15 is the L line, which, if used, functions similarly to the K line, providing a generic scan tool communication protocol. L line use is usually indicated if a pin is visible in this location on the vehicle’s DLC connector. TECHNICIAN TIP DLC pin IDs are standardized, although some Subaru vehicles use a different pin numbering system for their electrical connectors. Refer to the service information for any vehicle when working to identify which pins, and their function, are used in the DLC for the vehicle you are working on.

DLC Breakout Box The DLC breakout box (DLC BOB) connects the DLC to the scan tool, although it may also be used as a stand-alone tool. The DLC BOB allows for quick access to check any DLC pin for a voltage reading or to view a signal on a DSO.

You can verify system voltage at the DLC by connecting your DMM to pins 4 and 16. You should be very close to source voltage. A reading of 0 V indicates a ground or source fault. Move the negative lead to a known good ground. If you now have source voltage, there is a fault in the pin or wiring related to DLC pin 4. You can confirm an open on DLC pin 16 by connecting the DMM positive lead to battery positive and using the DLC BOB to connect the DMM negative lead to pin 4. If you now have source voltage, there is a fault in the wiring related to DLC pin 16. Pins 6 and 14 connect to the CAN bus. With vehicle power OFF, you can quickly check the CAN bus wiring for correct resistance. Most CAN systems use two terminating resistors of 120 Ω at each end of the twisted pair wiring. The resistors are wired in parallel so the resistance at pins 6 and 14 should be approximately 60 Ω. A value much lower or higher can indicate a fault in the CAN bus wiring. You can also use the DLC BOB to connect pins 6 and 14 to a two-channel DSO to view the actual CAN high and low signals (FIGURE 6-37). This may be necessary if there is a network-related DTC or the scan tool cannot communicate with any systems on the CAN network (FIGURE 6-38).

FIGURE 6-37 A DLC breakout box is a useful tool that works with your DMM and DSO to view voltages and waveforms. © Jones & Bartlett Learning.

FIGURE 6-38 Sample CAN Hi and CAN Lo waveforms for reference. The no signal value is 2.5 V. CAN Hi pulses approach 3.5 V; CAN Lo pulses approach 1.5 V. © Jones & Bartlett Learning.

The K line, pin 7, and L line, pin 15, can also be checked for correct voltage and to view their communication signals. Check for voltage by connecting the DMM positive lead to pin 7 or 15 and the negative lead to a known good ground. (You can use DLC pin 4 if you have verified it is functioning normally.) The voltage of this line can vary depending on the communication protocol, so compare your DMM reading with the related vehicle service information. You can also view the data transmission by connecting pins 7 or 15 to a DSO. Verify the waveform on the DSO with that in the service information. You can also check pins 4, 5, and 16 for voltage drop. Pins 4 and 5 are grounds. Connect the DMM negative lead to battery ground and the positive lead to either pin 4 or 5. Start the engine and not the reading. When testing pin 4 chassis ground, be sure to load the charging system by turning on the headlights, HVAC blower motor, and rear window defogger. The reading for pin 4 should be no more than 0.2 V. For signal ground voltage drop, move the DMM positive lead to pin 5 of the DLC BOB. The voltage drop should be less than 0.05 V (50 mV) with the engine running. You can also check DLC pin 16 for voltage drop. Connect DMM positive to battery positive and DMM negative to DLC BOB pin 16. With the engine running and several loads turned on, there should be less than a 0.2-V drop. Some DLC BOBs include LEDs that illuminate to indicate B+ and other signals. The use of this tool is a great time saver and allows the scan tool to be connected while you do pin checks of the DLC with your DMM or DSO. To connect the DLC BOB and perform voltage tests and view CAN waveforms on a DSO, follow the steps in SKILL DRILL 6-2. SKILL DRILL 6-2 Using the 16-Pin DLC Breakout Box The 16-pin DLC BOB allows for quick and accurate tests that can be done at the DLC. These include verifying DLC voltage at pin 16 and ground voltage drop at pins 4 and 5, and checking CAN resistance, CAN signals, and other network signals if available at the DLC.

1. Connect the BOB to the DLC. Some BOBs feature an LED that illuminates to indicate voltage is present (of course, you need to verify the voltage with a DMM for an exact reading).

2. The other cable on the BOB is available so you can connect the scan tool at the same time.

3. You can quickly verify voltage at pin 16. Connect the DMM positive lead to BOB pin 16 (note that some DMM test leads “plug” into the BOB pin receptacle). Connect the DMM negative lead to a known good ground. Pin 16 should be very close to battery source voltage with KOEO.

4. Testing the grounds at pin 4 or 5 should be done with the engine running (KOER). Connect the DMM positive lead to pin 4 or 5. Connect the DMM negative lead to the battery negative cable (this is the best ground point in the vehicle). Start the engine. The voltage drop between ground pin 4 or 5 and the battery negative post should be less than 50 mV. If it is much higher than this, over 100 mV, there is resistance in that ground circuit that can create erratic PCM (or other ECUcontrolled circuit) behavior, as this can affect input voltage values and output control voltage across the related load(s).

5. CAN uses terminating resistors across the CAN Hi and CAN Lo signal wires. You can identify their ECU location using the CAN system diagram from the service information. They are in parallel and there are usually two of them. The resistance value between CAN Hi and CAN Lo can be measured at DLC pins 6 and 14 to obtain a value of approximately 60 Ω. This test is done with the ignition OFF since we are measuring resistance. Connect the DMM test leads to pin 6 and 14 of the BOB (polarity does not matter for ohms resistance tests). Note the value on the DMM; it should be very close to 60 Ω.

6. A DSO can be connected to CAN using the BOB test points. Obtain a DSO from your instructor. This procedure will have you use two channels of the DSO. Connect channel A to pin 6 of the BOB. The signal lead goes to pin 6 and the ground goes to pin 4. Connect the channel B signal lead to pin 14 of the BOB and the ground to pin 4 if your leads can be doubled up. If not, connect it to a known good ground. Set the DSO to a 1- or 2-V/division scale and a 100 ms/division scale. This test can be done KOEO or KOER. There will be more activity with the KOER. Verify your DSO setup and CAN signals with your instructor.

7. This concludes the skill drill. Return all equipment to its storage location. Carefully remove test leads from the BOB, the DSO, and the DMM. All these tools are expensive and can easily be damaged if abused. © Jones & Bartlett Learning

OBD II Drive Cycles 6-6 Replicate OBD II component or system monitor test drive cycles as part of the strategy-based diagnostic process.

OBD II uses drive cycles as part of the requirement for the ECM/PCM to determine if input, output, or system operation is outside normal threshold limits. A drive cycle may include a sequence for how the vehicle operates to determine a component or system fault. Other drive cycles may require only that the engine be running for a set period of time. These faults can be detected within a few seconds after vehicle start provided they are not intermittent. The example shown in FIGURE 6-39 is for a mass air flow (MAF) sensor input signal fault P0102 or P0103. This DTC nomenclature is as follows:

FIGURE 6-39 Most OBD II DTCs integrate a drive cycle as part of the process to determine that a component or system is operating outside threshold limits. © Snap-on Incorporated.

P = Powertrain 0 = Generic DTC (same meaning for any manufacturer that uses this DTC) 1 = Fuel system-related DTC 02 or 03 are designated for MAF-related faults The service information provides specific steps the technician follows to prepare the vehicle and perform the drive cycle. The procedure shown requires that DTCs are cleared and then checks for a pending DTC after the engine is running for at least 5 seconds. If there is no DTC, then increase engine speed to 4000 rpm and use the scan tool menus to access readiness status for DTC P0102 or P0103. This allows the technician to view how the ECM/PCM software has judged the MAF sensor data: normal, abnormal, or incomplete. Now, you may be thinking, the vehicle came in for a check engine light ON concern. A MAF DTC was stored, why not just start doing some tests of the MAF and related circuit? With OBD II, not following procedures leads to comeback situations. Watch the master diagnostic technician where you work. This technician avoids condemning a component or jumping ahead of the

diagnostic process. They work fast but also work smart, and are familiar with the procedures you are learning about in this text. Accessing the related service information ensures the applicable drive cycle is understood by you, the technician. Shortcutting the process often leads to a comeback situation. TECHNICIAN TIP The examples shown in this section are based on using the factory scan tool. Menu access with aftermarket scan tools will vary, as will menu naming conventions for each vehicle manufacturer. This is why it is critical to follow the service information procedures, and when using an aftermarket scan tool, take the time to learn the available menu items that function to mirror factory scan tool software.

Some component or system related DTCs are based on drive cycles that require actual driving with specific criteria that must be met before the PCM software is able to determine that all is okay or a fault is present (FIGURE 6-40). This drive cycle is for DTC P0128, where the thermostat operation does not allow for proper engine warmup. A thermostat that is stuck partially to fully open allows coolant to circulate through the radiator, which inhibits bringing the engine up to operating temperature as quickly as possible. An engine operating below normal operating temperature usually has an increase in emissions, reduced performance, and more component wear.

FIGURE 6-40 Some component tests require that the vehicle be driven and that specific criteria are met for the drive cycle to run

and complete. © Jones & Bartlett Learning.

The DTC nomenclature is as follows: P = Powertrain 0 = Generic DTC 1 = Fuel system–related DTC 28 = Designated for thermostat operation fault(s) This drive cycle will run only if the engine coolant temperature is below 133° F and intake air temperature is between 32° and 95° F at engine start. Temperatures outside of these limits inhibit running the drive cycle for this DTC. For example, a vehicle staged outside waiting for you to be dispatched to bring it into your stall may be outside the intake air temperature limits if it is very cold or very hot outside. Use the scan tool data list to verify temperatures are within the limits. If yes, perform the drive cycle by driving at 50 mph for 15 minutes. Note that this is not easy to do where many shops are located, especially in metropolitan areas. Most repair shops have designated routes to follow for test drives that meet the various criteria outlined in the service information. To perform a DTC-related OBD II drive cycle, follow the steps in SKILL DRILL 6-3. SKILL DRILL 6-3 Performing a DTC-Related OBD II Drive Cycle 1. Take the scan tool along when going to bring the vehicle into your shop stall. This may seem odd to you, as you may be used to starting your diagnosis once you place the vehicle in your service bay. Many DTCs and drive cycles have temperature thresholds that may inhibit running a drive cycle or storing a DTC. The short drive from the vehicle staging area into the service stall may be enough engine running time to inhibit performing a drive cycle. This is why we want to get started before we start the engine and move the vehicle. 2. Connect the scan tool to the vehicle and turn the ignition ON but do not start the engine (KOEO). 3. Check for DTCs with the scan tool (Mode 3). Is a DTC present? If yes, before moving the vehicle, review the DTC enable conditions in the service information. Determine parameters such as engine temperature at vehicle start and others that are required to run the monitor test for this DTC. Write them on the repair order (or print them out). 4. Review PID (input/output data) with the scan tool (Mode 1) and compare the DTC enable criteria (e.g., intake air temperature and engine coolant temperature) to the enable criteria. Verify whether the related PID data are within the enable criteria conditions for the monitor to run if you perform the related drive cycle. 5. Review the DTC freeze frame data with the scan tool (Mode 2). The data inform you of vehicle operation when the DTC stored. You can determine vehicle speed, engine load, operating temperature, and more. This can be very helpful when performing the drive cycle and attempting to duplicate the conditions when the DTC stored. 6. You are now at a decision point: Is performing the drive cycle as part of your diagnosis necessary before driving the vehicle into your shop stall? If yes, then erase DTCs with the scan tool (Mode 4). Perform the drive cycle as described in the service information. If it is not necessary to perform the drive cycle, such as with a DTC P0116 for an ECT sensor out range that can be detected without driving, then proceed to the shop stall and continue diagnosis. Warning: Driving with a scan tool is considered distracted driving and is illegal in many states. Ask an assistant to drive as you describe the drive cycle and note PID data on the scan tool (Mode 1) or Monitor Status (Mode 6). Did the DTC store once the drive cycle finished? If yes, the fault is currently present and you are ready to continue the diagnostic

process. If there is no DTC stored, the fault may be intermittent. Follow diagnostic procedures for isolating the cause of an intermittent fault, such as the wiring harness wiggle test. 7. Follow the DTC diagnostic steps along with applying your component and system operating knowledge to isolate the cause of the fault. DTC P0128, for example, may be caused by a thermostat that is stuck open. Verifying thermostat operation would be a part of this DTC’s diagnostics. 8. The last step of the strategic diagnostic process is to verify that the fault is repaired. Part of the verification is to clear DTCs (Mode 4) and then perform the related drive cycle to verify the component or system is now operating correctly, verifying your repair has corrected the fault, and no other faults are present. Tech Note: Some component and system monitors will not run if certain DTCs are present, so making one repair can lead to another component or system now meeting enable criteria and setting a DTC due to a different fault. Skipping step 8 can lead to comeback situations. To a customer who sought a MIL ON fault diagnosis, having the MIL turn on during the drive home greatly erodes customer confidence in you and your shop’s work. 9. Return any tools and vehicles to their storage location upon verifying skill drill completion with your instructor.

SAFETY Driving with a scan tool is considered distracted driving and may be illegal in many states. Ask an assistant to drive as you describe the drive cycle and note PID data on the scan tool (Mode 1) or monitor status (Mode 6).

TECHNICIAN TIP Some component and system monitors will not run if certain DTCs are present, so making one repair can lead to another component or system now meeting enable criteria, and it sets a DTC due to a different fault. Skipping step 8 in Skill Drill 6-3 can lead to comeback situations. To a customer who sought a MIL ON fault diagnosis, having the MIL turn on during the drive home greatly erodes customer confidence in you and your shop’s work.

Many of the auxiliary emission components, such as EGR, secondary air, and the catalyst, require use of a very detailed drive cycle to verify component or system operation. The catalyst monitor drive cycle shown in FIGURE 6-41 has several parts and two distinct sections. The first part of the drive cycle required verifies heated oxygen sensor operation. It is done as follows:

FIGURE 6-41 Some monitors require very specific and complex test drives, such as the catalyst monitor. © Jones & Bartlett Learning.

Section A: Idle engine until oxygen sensor is at operating temperature. (Monitor PID data with the scan tool in Mode 1 and continue to section B once ECT data show 167° F or higher.) Section B: Drive the vehicle at 37 mph for 10 minutes with as steady a load as possible. Sections C and D: Accelerate quickly to 47 mph, hold steady for about 1 minute, then decelerate with vehicle in low gear to force fuel cut mode. Repeat three times. Section E: Idle the engine and use the scan tool to view heated oxygen sensor monitor test results (usually Mode 6 but can be Mode 5). Section F: Ignition OFF. Section G: Idle warmup (if just after the test drive, the vehicle should be ready). Section H: Steady drive at 47 mph for 10 minutes (or more). Section I: Engine idle for about 7 to 8 minutes. Section J: Accelerate to 50 to 60 mph and hold steady for 10 minutes (or more). Section K: Stop the vehicle. Review catalyst monitor test results using the scan tool (Mode 6). Drive cycles apply to all OBD II DTCs, even if no driving is involved. Where does this fall in the strategic diagnostic process? Step 2, gathering information, is correct; from this information, follow the procedures to verify the cause of the concern. Yes, there is overlap between diagnostic steps. Again, look to your master diagnostic technician as an example. A DTC for the ECT sensor or catalyst does not immediately lead to a visit to the parts department. This technician follows the procedures to perform the

related drive cycle to obtain the correct information to then begin following the appropriate strategy-based diagnostic tests using the drive cycle test results.

OBD II One-Trip and Two-Trip Diagnostic Trouble Codes OBD II DTCs are categorized based on the number of drive cycles, or trips, required for the DTC to turn ON the check engine light (MIL). The service information lists this information for each applicable input and output component and monitored system on the vehicle. A one-trip DTC illuminates the MIL when the monitored component exceeds malfunction thresholds on the first trip (FIGURE 6-42). These are classified as type A faults and can have a greater effect on power, fuel economy, and emissions.

FIGURE 6-42 OBD II DTCs may use one-trip or two-trip logic before the MIL is turned ON, indicating to the customer that a DTC has stored. © Jones & Bartlett Learning.

Two-trip DTCs set a pending DTC on the first trip when malfunction thresholds are detected (FIGURE 6-43). A pending DTC can be viewed with the scan tool, but the MIL remains OFF for most DTCs (there can be exceptions). If the component or system fails the next consecutive trip, then a DTC sets, a freeze frame stores, and the MIL turns ON.

FIGURE 6-43 Two-trip DTCs set a pending DTC on the first trip where a fault is detected. The MIL remains OFF but you can usually view a pending DTC with a scan tool using Mode 1. © Jones & Bartlett Learning.

TECHNICIAN TIP A consecutive trip requires that the drive cycle criteria be met for the applicable DTC. The catalyst monitor drive cycle explained earlier is an example of this (FIGURE 6-44). A customer starts off in the morning and drives 18 miles to work. The route in the morning has very little traffic so the drive includes sufficient steady cruise to complete the drive cycle. The catalyst monitor completes and fails setting a pending DTC and the MIL remains OFF. The customer goes out for lunch, a short 5minute drive in moderate traffic. The monitor does not run so this does not count as a catalyst monitor trip. While at lunch, the customer receives a call that his child is sick at school and must be picked up. The customer drives home and there is very little traffic. The catalyst monitor runs, the monitor test results exceed limits, and it fails. A DTC stores and the MIL turns ON, as the monitor ran a second time. If the monitor test results indicated all was okay, the pending DTC would erase, the MIL remain OFF, and the monitor would complete as PASS.

FIGURE 6-44 The catalyst monitor usually requires two consecutive drive cycles to set a DTC and turn the MIL ON. The first trip stores a pending DTC. © Jones & Bartlett Learning.

OBD II System Monitors OBD II monitors components, software adaptation for fuel control, cylinder misfires, and emission control systems for proper operation. There are two types of monitors: continuous and noncontinuous. Continuous monitors are active at all times when the engine is running and include the following: Component monitor Fuel system monitor Misfire monitor The component monitor includes most of the input sensors that are used by the PCM to calculate fuel injector on-time and ignition time. Some output actuators are also monitored, as are components such as the thermostat, by means of input data that fall outside of normal operating parameters. Examples include the following: MAF fault: The MAF is a critical sensor for the engine load calculation. A fault that inhibits MAF data to the PCM usually causes the PCM to rely on engine rpm and throttle position, reducing the fuel map calculation accuracy. All aspects of engine performance suffer from this type of fault. Thermostat fault: A thermostat that is stuck open increases engine warmup time. Although the thermostat is not directly monitored, the PCM can set a DTC for warmup time that takes too long by monitoring the ECT data. This type of fault can increase engine wear, increase emissions, and reduce fuel economy. Camshaft VVT actuator fault: A camshaft VVT actuator controls the advance or retard position of the camshaft. The PCM monitors camshaft position from the CMP sensor data. The PCM provides an output signal to the actuator. An actuator fault inhibits proper camshaft position advance or

retard. This type of fault can result in reduced engine output, poor idle quality, and even stalling. The fuel system monitor tracks fuel injector on-time variations based on air-fuel ratio feedback data from the oxygen or air-fuel ratio sensor(s). This allows the PCM to adapt the fuel map to a wide variety of factors that without adaptation could create drivability issues. Examples include engine wear, injector flow rate variations, and fuel pump pressure. The fuel system monitor data is called fuel trim and is usually displayed as a percentage value using a scan tool in Mode 1 data list (FIGURE 6-45). Fuel trim adjustments that exceed normal levels set DTCs for excessive lean or excessive rich conditions. Either condition affects engine performance and emission levels.

FIGURE 6-45 The fuel monitor displays data under short-term and long-term fuel trim, usually with a percentage of value that deviates from the fuel map injector on-time values. © Jones & Bartlett Learning.

The misfire monitor relies on CKP and CMP data along with ignition event feedback data from the ignition coils (on many vehicles). The PCM uses the data to count misfires that are from one or more cylinders or are random. The PCM can determine a misfire from crankshaft speed variations from the misfire events. The CMP sensor data help isolate the crankshaft speed variations to the cylinder that is on the power stroke when the misfire occurred. Many vehicles now also monitor a signal generated by the ignition coil for each cylinder when normal spark events occur. The absence of this signal also assists the PCM in determining that a misfire occurred and in what cylinder. Misfire DTCs set when the misfire count exceeds a threshold based on engine rpm. Severe misfires that are occurring at a very high rate

based on engine rpm cause the MIL to flash during the conditions when they occur, such as heavy engine load. The goal of the flashing MIL is to alert the driver to reduce engine load or the related operating condition that is creating the high misfire rate. Misfires reduce engine power and can increase emissions, though most PCMs shut OFF the injector for the affected cylinder to protect the catalyst from damage. Excess fuel in the exhaust creates an afterburn effect that raises exhaust gas temperature. A catalyst that gets too hot can cause the supporting substrate to melt or even disintegrate. Noncontinuous monitors run only when applicable drive cycle enable criteria are met and include the following (FIGURE 6-46):

FIGURE 6-46 Noncontinuous monitors test components and systems that control vehicle emissions. These monitors run only when the enable criteria are met. © Jones & Bartlett Learning.

Oxygen and air-fuel ratio sensor(s) operation Catalyst operation Secondary air system operation EGR-related system operation Evaporative emission system purge operation and system leak check OBD II monitors are viewed using the scan tool. Most scan tools offer direct access to monitor data through a menu selection or by accessing Mode 6 test results. Continuous monitors can be identified by their name and that they are “Available.” Noncontinuous monitors display as follows:

N/A: Indicates that they are not available on the vehicle Complete: Indicates that the monitor has run and the test results are stored Incomplete: Indicates that the monitor has not run at all or has run for only one trip and must run for a second trip to complete Noncontinuous monitors can set a DTC and related test results only when they complete (FIGURE 647). A one-trip monitor passes or fails on the first trip where the drive cycle criteria are met and the trip completes. Two-trip monitors require two consecutive failed trips to set a DTC. On the first failed trip, the test status still displays as incomplete. The status changes on the second consecutive trip, where drive cycle criteria are met and the trip completes (FIGURE 6-48). If the test results exceed thresholds for both trips, the data store and a DTC sets, turning on the MIL.

FIGURE 6-47 Monitor data can be viewed using the scan tool. © Jones & Bartlett Learning.

FIGURE 6-48 OBD II monitor test results can help you determine how severe the condition is and can also be used after repair to verify the system is functioning normally. © Jones & Bartlett Learning.

Monitor test results can be viewed from the Mode 6 monitor screen display (FIGURE 6-49). The data can help you determine how far the value exceeds the minimum or maximum thresholds. It can also be used after you repair the cause of the fault during the final step of the strategy-based diagnostic process. Follow the applicable drive cycle and verify the monitor completes and passes. View the test results to verify that the system is now functioning normally and is not near a minimum or maximum threshold.

FIGURE 6-49 Monitor test results are based on hexadecimal data; however, most scan tools now automatically convert these data. © Jones & Bartlett Learning.

The service information provides detail on how the monitor test results are calculated. Most OBD II vehicles now convert these data for display on the scan tool so no hexadecimal look-up for test ID or component ID is required. Early OBD II vehicles, many before MY 2000, require that you look up the hexadecimal conversion data. Fortunately, most service information systems provide a link to these data to reduce time in searching for it.

OBD II Data List Scan tools offer viewing of live data for engine control inputs and various actuator output states (ON or OFF). The data are based on input signals that have been processed by the ECM/PCM. The scan tool connects to the ECM/PCM via the 16-pin OBD II DLC. Vehicles since MY 2008 connect using CAN bus protocols. The data shown, however, could be affected by not only a faulty sensor input or output actuator, but by poor grounds or resistance in the related wiring. Be aware that even if the data looks okay, it is based only on the actual voltage that is at the ECM/PCM. A sensor ground with excessive resistance that creates a voltage drop of 500 mV could cause all sorts of drivability issues, but the data may be within the normal limit range but is actually out of range for the current engine conditions, such as temperature, engine speed, and load. Data that are within the range limit but skewed due to circuit resistance or other fault may not set a DTC (FIGURE 6-50). These faults require you to go beyond the use of the data list and use your DMM or DSO to observe the signal at the PCM and at the component. If the value is not the same, there is resistance or some other cause of signal degradation that must be isolated and repaired.

FIGURE 6-50 Parameter data are viewed live using the scan tool. © Jones & Bartlett Learning.

The service information provides valuable information for using scan tool data. In FIGURE 6-51 you can see the measurement range, normal values, and whether the data are stored as part of a freeze frame.

FIGURE 6-51 The service information provides data range values and how the value is determined. © Jones & Bartlett Learning.

The service information also has a list of fail-safe strategies when a sensor circuit or control system has a fault. For example, the sample vehicle shown in FIGURE 6-52 uses a substitute engine coolant temperature value of 176° F. This is important for you to know, as some scan tools may show the fail-

safe value on the data list, causing you to interpret this as a system that is okay rather than having a fault.

FIGURE 6-52 Fail-safe data are listed in the service information. This can be helpful because on some vehicles the fail-safe value appears on the scan tool data list. © Jones & Bartlett Learning.

The scan tool data list and service information are critical to step 2 of the strategy-based diagnostic process, Research Possible Faults and Gathering Information. Use of the two together allows you to isolate data that are out of the normal range, which helps you prepare for step 3 of the process, focused testing.

WRAP-UP Ready for Review OBD II has been fully implemented on MY 1996 and newer vehicles. A few vehicles began to phase in use of OBD II features, including the 16-pin DLC, starting in 1994. CAN OBD II is required on MY 2008 and newer vehicles for scan tool communication with the vehicle. Some vehicles had this feature prior to this deadline. This requirement applies only to the use of the CAN for scan tool communication, but most manufacturers use the CAN system for engine control networking with other vehicle ECUs. The 16-pin OBD II DLC has designated pin locations for B+, grounds, and different types of communication protocols. A DLC breakout box (BOB) can be used to allow easy access to OBD II pins for DMM or DSO testing. A drive cycle details the vehicle operating parameters that must be met for the ECM/PCM to determine component or system status for DTC thresholds. Some DTCs may require one trip to set, whereas others require two consecutive trips to set. Continuous monitors begin operation every time the key is in the run position. Each DTC has drive cycle criteria that must be met for the monitor to run. Some are very simple whereas others require specific items be met before the monitor can run. Noncontinuous monitors are designated by OBD II and have specific drive cycle enable criteria that must be met for the monitor to run. OBD II DTCs also store a set of freeze frame data that are very helpful to determine which vehicle conditions were present when the DTC stored, including engine rpm and temperature, and vehicle speed. OBD II scan tools display live input sensor data, output actuator command status, and engine control functions using the data list function. OBD II scan tools offer bidirectional communication with the ECM/PCM, allowing the technician to turn actuator outputs ON or OFF and adjust air-fuel ratio to determine operational status of the related component. OBD II scan tools may offer advanced functions that can assist your diagnosis, including ondemand running of the EVAP monitor.

Key Terms Continuous monitors OBD II monitors the fuel system, engine misfires, and components (inputs and outputs) continuously when the ignition is ON and when required, such as for misfires, when the engine is running. Data link connector (DLC) The underdash connector through which the scan tool communicates to the vehicle’s computers; it displays the readings from the various sensors and can retrieve trouble codes, freeze frame data, and system monitor data. Drive cycle Defined by the manufacturer, it verifies the operation of a power train input sensor, output actuator, or the integrity of a system (e.g., EGR). Each is defined by the related monitors with which it is associated and is detailed in the service information for each monitored component or system. DTC structure Standardized format followed by OBD II powertrain DTCs. It begins with the letter P and is followed by four numbers or a combination of numbers and letters. Each character is associated with the type of DTC, the related system, and component. Hexadecimal A base 16 method of counting. Noncontinuous monitors Monitors that run only once per drive cycle. On-board diagnostic first generation (OBD I) system The first generation of onboard diagnostic systems that originated for California vehicles. On-board diagnostic second generation (OBD II) system The second generation of onboard diagnostic systems, which have been in effect for all U.S. vehicles since 1996. Scan tool modes Scan tool communication with the PCM follows OBD policy and regulations from related agencies, including the EPA and CARB. Trip A completed drive cycle that is also associated with DTCs. Some components or systems require only one where a fault is detected for a DTC to store and turn the MIL ON. Others require two consecutive trips with a detected fault before a DTC stores and the MIL illuminates. Vehicle Emission Control Information (VECI) A decal located under the hood in a variety of locations: On top of the core support, on a strut tower, or on the underside of the vehicle’s hood are frequently used positions. The decal lists the installed emission control devices, the year the vehicle’s emission system conforms to, and which OBD system is used.

Review Questions 1. CAN OBD II was required on all vehicles by which model year? a. 1996 b. 1999 c. 2003 d. 2008 2. OBD II DTCs that are generic, meaning their definition is the same when used by different manufacturers, use which numbers in the second alphanumeric position? a. 0, 1 b. 0, 2 c. 1, 1 d. 1, 3 3. CAN Hi and CAN Lo signals are in which pin locations of the DLC? a. 7, 15 b. 6, 14 c. 1, 10 d. 2, 8 4. Which of the following statements is correct? a. A freeze frame must store all data for all PIDs. b. An incomplete monitor indicates the related system or component has a fault. c. Check mode narrows the fault thresholds to help identify a faulty component or system. d. Drive cycle operation is not affected by ambient temperature. 5. All of the following detail the Active Test scan tool function EXCEPT: a. allows substitution of a known good value for input sensors. b. can turn ON a normally OFF output component, such as the EVAP vent valve. c. can turn OFF a normally ON output component, such as a fuel injector. d. allows for adjustments to the air-fuel ratio. 6. What is the function of the K line? a. Provides the fastest speed of scan tool sensor data b. Allows for generic scan tool communication c. Active test control signals use this DLC assigned pin. d. Mode 6 test hexadecimal data are accessed through this DLC assigned pin. 7. A transmission DTC will use which of the following alphanumeric characters? a. P b. B c. C d. U 8. PID and CID data may use which of the following? a. Only alphanumeric identification b. Binary code you must convert to interpret c. SAE designated English terminology for all data d. Hexadecimal identification 9. The data list provides live vehicle data. The technician uses this for all of the following EXCEPT: a. isolating data that are at a threshold limit indicating an open or short sensor input circuit. b. determining whether data are rational for the condition. c. looking for fail-safe data being substituted for actual sensor input data.

d. determining whether actuator output signals are functioning correctly. 10. The DLC breakout box allows access for all of the following EXCEPT: a. oscilloscope lead access for CAN Hi and CAN Lo. b. verifying voltage at pin 16. c. verifying signal ground at pin 8. d. verifying K line signal at pin 7.

ASE Technician A/Technician B Style Questions 1. Technician A says OBD II DTCs follow a standard protocol for all manufacturers selling gasoline and diesel passenger vehicles in the United States. Technician B says DTC P1401 is a manufacturerspecific DTC. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B 2. Technician A says a two-trip DTC with a one-trip fault detected will illuminate the MIL and store a freeze frame. Technician B says that some DTCs are permanent and require driving the vehicle through the applicable drive cycle to erase. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B 3. Technician A says that most input sensors are part of specific system monitors. Technician B says reviewing input sensor voltage thresholds are part of the diagnostic process? Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B 4. A vehicle is in the shop for P0301, misfire cylinder 1. Technician A says the scan tool may offer an active test to determine whether the fault is caused by the fuel injector. Technician B says some scan tool software can perform an active test to determine whether one or more cylinders are not contributing equally. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B 5. A vehicle is in the shop for a check engine light ON concern. The check engine light is currently OFF when the engine is running. Technician A says freeze frame data may be available to review. Technician B says freeze frame data can provide information, such as engine and vehicle speed, so you can test-drive the vehicle under similar conditions to duplicate the customer concern. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B 6. Technician A says the scan tool may offer functions to set DTCs under tighter than normal DTC thresholds. Technician B says that if the scan tool does not communicate with the vehicle, the only option for diagnosis of the fault is to replace the ECM/PCM. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B 7. Technician A says a DLC breakout box offers easy access for verifying CAN and other signals at the DLC. Technician B says all scan tool software converts hexadecimal data to readable text. Who is

correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B 8. Technician A says after repairing a fault that set a DTC, the final diagnostic step is to erase DTCs. Technician B says a no-start condition may not set a DTC but you can use the scan tool data list to view engine speed to help determine whether there is a CKP fault. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B 9. Technician A states that input and output values on the data list always reflect actual conditions at that moment in time. Technician B says the diagnostic procedure may have you disconnect a sensor connector and then view the scan tool data list to verify the value. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B 10. Technician A says some sensor or system drive cycles will not run if the ambient or engine coolant temperature is out of range. Technician B states that two-trip DTCs usually require the failures to be consecutive to store a DTC. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B

© Jones & Bartlett Learning.

CHAPTER 7

Continuous Monitor Diagnostics LEARNING OBJECTIVES After studying this chapter, you should be able to: 7-1

Identify continuous monitors.

7-2

Diagnose diagnostic trouble codes (DTCs) related to the component monitor.

7-3

Diagnose misfire DTCs.

7-4

Diagnose fuel trim DTCs.

YOU ARE THE AUTOMOTIVE TECHNICIAN A check engine light concern leads you, the technician, to DTC P0171, Fuel System Too Lean (FIGURE 7-1). Which of the following will most likely be required for your diagnosis?

FIGURE 7-1 A check engine light in this case is due to DTC P0171, Fuel System Too Lean. © Jones & Bartlett Learning.

View KOER data list parameters. Review DTC-related service information. View Mode 6 data. View Mode 7 data. Review freeze frame data. Inspect for intake system air leaks. Perform MAP and/or MAF inspection and related testing. Check for an exhaust leak. Inspect HO2S or AF ratio sensors. Verify proper fuel pressure.

Introduction Monitor-based diagnosis is more than following a troubleshooting flow chart and making a repair. It requires a thorough review of the related diagnostics and understanding that a fault in one sensor input or actuator output can prevent the monitor for another system from running. Without this knowledge, the technician may feel the vehicle is repaired and ready for return to the customer. What can happen, and often does, is that with the initial fault corrected and DTCs cleared, other monitors that were not running now run during the customer’s drive home or to work the next day and the check engine light (MIL) turns ON, but for a different DTC from a monitor that was unable to run due to the initial fault. Unfortunately, the customer interprets the MIL turning ON as the same fault for which they brought the vehicle in for diagnosis. This chapter and the monitor-related chapters that follow will prepare you to diagnose OBD II monitor faults with the required knowledge to ensure the vehicle monitors run and pass and there is no comeback situation.

OBD II Continuous Monitors 7-1 Identify continuous monitors.

OBD II monitors vehicle engine and transmission performance and is designed to illuminate the check engine light when a malfunction occurs that will affect vehicle emission levels 10% beyond normal limits. Some systems are monitored continuously, meaning they are monitored at all times when the engine is running (FIGURE 7-2). Other systems are monitored when specific enable criteria are met. This chapter covers the three continuously monitored systems:

FIGURE 7-2 OBD II monitors are listed on most scan tool displays. © Jones & Bartlett Learning.

Component (sometimes called comprehensive) monitor Misfire monitor Fuel system monitor

Continuous Monitor Operation

As soon as the ignition is turned ON, the PCM (powertrain control module, but in some vehicles, the ECM and TCM may be separate units) begins to monitor sensor data that are part of the comprehensive monitor. Upon engine crank, additional data are monitored, and once the engine is running, the comprehensive and misfire monitors are fully functional. The fuel system monitor begins to function once the HO2S or air-fuel (AF) sensor(s) reach operating temperature and the PCM enters closed loop fuel control. Continuous monitors are viewed on the scan tool Mode 6 monitor screen and usually show “OK” or “Available” next to their name (FIGURE 7-3). This indicates that these monitors are currently operating and their related data are under constant review by the PCM software. Continuous monitors cease operation once the ignition is turned OFF.

FIGURE 7-3 Continuous monitors are shown on the scan tool. © Jones & Bartlett Learning.

Component Monitor 7-2 Diagnose diagnostic trouble codes (DTCs) related to the component monitor.

The component monitor functions to evaluate primarily PCM input sensors for open or short circuits and sensor data that are out of normal range. The component monitor is part of the PCM programming and operates continuously when the engine is running and for some inputs, as soon as the ignition switch or start button is activated. Other components are monitored once the engine is running or when specific enable conditions are met. Examples of enable conditions include ambient temperature at engine start and any DTCs stored that may impact component operation and related PCM judgment of the data as okay or out of range. The PCM continuously monitors component input and output data for operation that does not exceed normal limits and in some cases if the data are rational for the current vehicle operating conditions. Sensor input or actuator output data that exceed limits or are determined not to be rational for current engine operating conditions store a DTC. The DTC provides the foundation for a technician to apply the strategic diagnostic process. Let’s use the engine coolant temperature (ECT) circuit as a continuous monitor example (FIGURE 7-4).

FIGURE 7-4 DTC information includes a description, possible causes, and monitor strategy, in this case continuous, which serves as a foundation for the technician’s diagnostic strategy. Note that this DTC has the PCM use a fail-safe value for ECT data. © Jones & Bartlett Learning.

Description

Detection of an ECT open or short circuit in a sensor input results in the following: ECT DTCs store immediately after fault detection (one-trip detection logic). MIL is illuminated. The PCM substitutes a fail-safe sensor value that is used to allow for as normal as possible engine operation (FIGURE 7-5).

FIGURE 7-5 The PCM substitutes a fail-safe value to allow for as normal as possible engine control when a DTC stores for some components, such as the ECT sensor circuit. © Jones & Bartlett Learning.

Description PCM input sensors and other data items that are part of the component monitor are detailed in the vehicle service information and may be referred to as Advanced Diagnostics. Accurate diagnosis of engine performance concerns and MIL ON diagnosis requires the service technician understand the elements of advanced diagnostics. The ECT DTC P0115, P0117, and P0118 description provides details applicable to engine coolant temperature circuit faults as follows: ECT circuit open or short ECT circuit low input (most likely a short to ground) ECT circuit high input (most likely an open circuit) Additional data show how long the data must be out of range and how many trips are required for the DTC to store. The ECT DTCs store after the sensor data are out of range for 0.5 second and use one-trip detection logic. The MIL turns ON (illuminates) when the DTC stores and a freeze frame is saved. This vehicle’s PCM substitutes a fail-safe ECT value of 176°F when an ECT DTC occurs. This helps the PCM maintain normal engine operation as much as possible. Cold engine start is affected, as the fail-safe value indicates a warm engine, where less fuel is required than in a cold engine, resulting in a rough running condition or a start/stall condition. To verify continuous monitor operation, follow the steps in SKILL DRILL 7-1. The continuous monitor stores DTCs when input or output data are not rational for vehicle conditions (FIGURE 7-6). DTC P0128 stores when the ECT data do not increase at a normal rate after a cold start. Some service information also lists possible causes for the related DTC, the thermostat, or ECT sensor in this example.

FIGURE 7-6 The component monitor is also used to verify whether a component’s operation is within the normal operating parameters. This example could be caused by a stuck open thermostat that does not allow the engine to reach normal operating temperature within the normal time limit. A DTC stores for this condition because it has an effect on emission levels, fuel economy, and engine performance.

© Jones & Bartlett Learning.

Description The service information usually provides a monitor description for each of the continuous monitored items. The sample shown describes monitor strategy and what temperature in this example causes a DTC to store if it is not reached within 11.5 minutes (690 seconds). Monitor strategy is basically a list of which DTCs are stored, the related component(s) monitored, whether the monitor is continuous or noncontinuous, how long the fault must be present, when the MIL turns ON after DTC fault detection, and any sequence of operation related to how the fault is detected. Enabling conditions may be very simple or more complex. The ECT sensor monitor is very simple and runs even if any other DTCs are stored. This is because it is a distinct circuit and even if the MAF, MAP, IAT, or another sensor has stored a DTC for some type of circuit or component issue, the ECT voltage data can still be accurately monitored by the ECM/PCM (FIGURE 7-7).

FIGURE 7-7 Enabling conditions are the requirements for the component monitor to assess the operation of a component. © Jones & Bartlett Learning.

Description Some DTCs have very specific enabling criteria. The enabling criteria or conditions are what must be met for the monitor to function. From the list shown in FIGURE 7-8, the monitor for the thermostat on this sample vehicle will not function if any of the following are present:

FIGURE 7-8 Some components are monitored under very specific criteria that include engine temperature and that no related DTCs are stored. © Jones & Bartlett Learning.

Description DTCs listed in the enabling conditions are stored. Battery voltage is below 11 V. Engine rpm is below 400 or above 4000. Engine coolant is below 167° F or above 212o F. SKILL DRILL 7-1 Verifying Continuous Monitor Operation

1. Obtain your assigned vehicle and scan tool from your instructor. 2. Connect the scan tool to the DLC. 3. Turn the ignition ON, engine OFF (KOEO). 4. Verify there are no DTCs present. If there are, erase them and recheck. If a DTC(s) is present, let your instructor know. This skill drill functions best when no DTCs are present. 5. Select Mode 6 monitors from the scan tool function menu. The component monitor should show “Available”, indicating it is operating. 6. Refer to the service information to locate the intake air temperature (IAT) sensor (it may be part of the MAF sensor on some vehicles) and related DTC diagnostics for an open IAT circuit (high voltage reading). Note how much time is required before a DTC stores and whether the PCM uses a fail-safe IAT value when a DTC stores. 7. Start the engine and then disconnect the IAT (or MAF) connector. 8. Check for DTCs. Did a P0113 DTC set? 9. Select data list (Mode 1) and note the IAT value. An open circuit should display data showing the IAT as a very low temperature value or, if a fail-safe is used, it may show the fail-safe value.

TECHNICIAN TIP Many PCMs employ a fail-safe value to keep the engine performance as normal as possible or allow the engine to run long enough to seek assistance. An IAT fail-safe will has very small effect on engine performance; however, if you do not realize the PCM is using a fail-safe value and you have an IAT DTC, then you may assume that the sensor and related wiring are okay when in reality there is a fault present.

10. Shut the engine OFF. Reconnect the IAT sensor connector. 11. Turn the ignition ON, engine OFF (KOEO). Erase DTCs with the scan tool (Mode 4). 12. Verify the MIL is now OFF and no DTCs are present. Select Mode 1 and verify the IAT value is now indicating the intake air temperature. 13. Turn the ignition OFF and disconnect the scan tool from the DLC. Power the scan tool OFF. Return the scan tool to its storage location. Verify with your instructor that this skill drill is complete.

TECHNICIAN TIP The data are very important. For example, this DTC will not set if there is an ECT DTC stored. A technician who only diagnoses and repairs the ECT circuit may miss that other monitors were not enabled. Releasing the vehicle to the customer without a thorough test drive following the universal driving pattern could result in the check engine light turning ON during the customer’s drive home since the ECT fault has been corrected but another fault is present and the enabling conditions are now met.

Case Study: Component Monitor Diagnostic

A vehicle is in your shop stall for DTC P0118, ECT sensor high input. High input means the ECM is sensing very close to the 5-V reference signal voltage. This is an abnormally high voltage and is most often caused by an open circuit (FIGURE 7-9).

FIGURE 7-9 P0118 stores when the ECT sensor circuit voltage is about 4.9 V for this vehicle. © Jones & Bartlett Learning.

The technician reviews the wiring diagram included in the DTC diagnostics (FIGURE 7-10). The technician connects the scan tool and notes that the scan tool data list parameter ID (PID) for the ECT is showing –40o F. Reviewing the DTC service information, the technician has verified the fault is current (happening right now) and should continue knowing that an open circuit in any of the following could be the cause:

FIGURE 7-10 The ECT wiring diagram provides connector pin information, including which is for input voltage and which is for sensor ground. Note that the actual engine control wiring diagram may be needed to determine wire color and component location. © Jones & Bartlett Learning.

Description Open between PCM E26 pin 95 and ECT E47 pin 2 Open between ECT E47 pin 1 and PCM E26 pin 96 Open in the ECT sensor Faulty PCM Refer to the DTC diagnostics (FIGURE 7-11) for the test procedures, which isolate the fault to an open in the wiring harness. Note that there is also a section for a short in the harness, but that does not apply to this vehicle. The first test is to disconnect the ECT connector and use a jumper lead to short pins 1 and 2 of the ECT connector together. This provides a quick check of both wires. If the wires are okay, then the scan tool data list will show a short condition and the ECT scan tool data list will show a PID value of 275o F.

FIGURE 7-11 The DTC diagnostics offer a path for an open in the harness or a short in the harness. © Jones & Bartlett Learning.

Description The technician performs this test and the data list still shows –40o F. The DTC diagnostics then direct the technician to check for continuity on the wires between the ECT and ECM. The tech could do this but applies the circuit knowledge that usually saves time. The voltage at pin 2 of the ECT connector should be 5 V with the key ON and the connector disconnected from the sensor. The technician checks and

there is 5 V at pin 2. The technician then reconnects the connector to the ECT sensor and checks voltage at pin 1. There is 5 V. This indicates that the sensor is okay, because there is continuity through it, and it is not failed open. It also indicates that the fault appears to be in the circuit ground. The technician then disconnects the connector from the ECT again and, with the key OFF, checks continuity from pin 1 to the sensor ground on the engine block. The DMM shows OL, indicating an open on this wire. The technician then follows the DTC diagnostics for checking the resistance between the ECT connector pin 1 and pin 96 of the ECM connector and notes a reading of OL. There is an open circuit fault in this wire. The technician inspects the harness and locates the open and repairs the wire. All connectors are then reconnected and the vehicle is started. The DTC is cleared, the MIL is now OFF, and no DTC has returned. The data list now shows actual engine temperature. The technician does a final check to ensure all connectors are installed correctly and the wiring harness is routed properly. Note that the technician still has one task to complete before finalizing the RO. This DTC can cause many other system monitors not to run. If the technician stopped here, the customer would drive the vehicle and all these monitors that had not run, now can. This could lead to another DTC storing and the MIL turning ON. To the customer, this is the same concern that brought them into the dealer and the repair just paid for was not done correctly. The technician performs a drive cycle to complete critical monitors related to this DTC, including fuel system, air-fuel ratio sensor, and catalyst operation. Once it is verified that these monitors ran, are complete, and passed, the technician can complete the RO and return the vehicle to the customer.

Misfire Monitor 7-3 Diagnose misfire DTCs.

The misfire monitor is continuous, but unlike the component monitor, which begins monitoring many of the sensor input data as soon as the ignition is ON, the misfire monitor begins to function after the engine starts (FIGURE 7-12). The misfire monitor relies primarily on data from the crankshaft position sensor (CKP) and the camshaft position sensor (CMP). The crankshaft data can detect a misfire when the CKP data indicates a cylinder did not produce power output due to a misfire and the crankshaft speed reduced as a result. The camshaft position sensor supplies the data to identify which cylinder had the misfire. The misfire monitor uses a counter to keep track of cylinder misfires when specific thresholds are met. A DTC stores when the misfire count exceeds the limit and could cause excessive emissions or damage emission system components, specifically the catalytic converters. A severe misfire would cause the MIL to flash on and off during the severe misfire event. This is designed so that the driver avoids operating the vehicle under conditions when the severe misfire occurs (such as hard acceleration) to prevent damage to the catalysts. Misfires that cannot be isolated to a particular cylinder set DTC P0300 for a random misfire condition.

FIGURE 7-12 The scan tool displays monitor test results, including the misfire monitor. Misfire counts may also be displayed on the data stream for some vehicles and scan tools. © Jones & Bartlett Learning.

The misfire monitor requires two-trip logic to set a related DTC. The misfire monitor “counts” the number of misfires for each cylinder. Misfire counts that exceed the manufacturer’s threshold amount

sets a preliminary DTC on the first trip but the MIL remains OFF. Misfire counts that exceed the threshold on the second consecutive trip set a DTC, and the MIL turns ON. The threshold for the sample vehicle shown is as follows: 10 to 70 misfires per 1000 crankshaft revolutions occur immediately after engine start 10 to 70 misfires per 1000 crankshaft revolutions occur four times The DTC identifies the cylinder that is misfiring, P0301, would relate to cylinder 1. Misfiring in two or more cylinders that cannot be identified specifically to each cylinder sets a random misfire DTC, P0300. Severe misfire conditions that could damage the catalytic converters cause the MIL to flash ON and OFF during the misfire event (FIGURE 7-13). The threshold for a severe misfire on this sample vehicle is as follows:

FIGURE 7-13 A severe misfire causes the MIL to flash. This is done to encourage the driver to reduce engine load or to seek service as quickly as possible. © Snap-on Incorporated.

At high engine speed, a sufficient number of misfires to cause catalyst damage is detected within 200 crankshaft revolutions one time (FIGURE 7-14).

FIGURE 7-14 A cylinder misfire can allow unburned fuel to enter the catalyst. This can overheat the catalyst substrate, causing it to deform or break apart. This type of damage requires catalyst replacement. © Jones & Bartlett Learning.

At normal engine speed, a sufficient number of misfires to cause catalyst damage is detected three times. The diagnostic service information also lists possible causes for misfire faults, including ignition circuit faults, fuel delivery faults, and mechanical related faults. The scan tool displays misfire count data. This may be part of the standard data list or part of continuous monitor test results (FIGURE 7-15).

FIGURE 7-15 Scan tool misfire count data. © Jones & Bartlett Learning.

OBD II vehicles may display data in hexadecimal format only, requiring that it be converted. A scan tool that displays data in hexadecimal format requires that you look up the monitor ID and test ID and scale in the related service information (FIGURE 7-16). The scale for this sample vehicle is a simple multiplier of 1, which means the value you see is the actual misfire count. Most recent vehicles and scan tools list the misfire data by name.

FIGURE 7-16 Some misfire monitor information is provided in hexadecimal format. © Jones & Bartlett Learning.

Description The misfire monitor in this sample vehicle will not run if the listed DTCs have stored, as these may contribute to a misfire condition. The following conditions must be met for the monitor to run: TECHNICIAN TIP Older OBD II vehicles display test ID and component ID data in a hexadecimal format noted by what looks like a dollar symbol with only one vertical line. You may have to use the service information to decipher each test and component ID. Note that in this example, highlighting component ID 21 on the scan tool brings up a popup that describes what the test and component IDs are. There may also be a required formula that you then apply to convert the test result data to a usable value for diagnosis. To perform a no-code misfire diagnosis, follow the steps in SKILL DRILL 7-2.

SKILL DRILL 7-2 Diagnosing No Code Misfire

1. When the vehicle comes into the service facility for a misfire concern, first verify the complaint.

2. Using a scan tool, look at the misfire monitor to determine whether there is a misfire. If the misfire monitor picks up a misfire it should be present on the misfire monitor.

3. Once you know which cylinder has a misfire, you can start the diagnostic process.

4. Once the visual inspection is completed, ohm out the ignition coil primary.

5. Verify the ignition coil has key ON power and also PCM actuation on the ground side of the connector.

6. Remove the ignition coil on the affected cylinder and inspect the spark plug well for oil or other contamination. If a valve cover is leaking oil into the well, that must be fixed first before continuing with an ignition diagnostic.

7. With the ignition coil removed, remove the spark plug so you can inspect the electrode and gap. As you inspect the spark plug, look to see if the electrode is contaminated with coolant, oil, or some other substance. Also look at the insulator for any signs of cracking or carbon tracking. While the spark plug is out, check the gap between the electrode and the ground strap and verify that it is in specification.

8. If nothing is found with the ignition components that validate a failure, it is time to check the cylinder for compression. To make any ignition event happen, the engine needs to make compression within the cylinder for proper ionization. Obtain a compression gauge and conduct a compression test. Validate the readings with specifications for the engine. If the compression is low, you need to fix the mechanical issue before continuing with an ignition issue.

9. Document findings and discuss next steps with the service advisor. © Jones & Bartlett Learning

Battery voltage is 8 V or higher. Engine rpm is between 400 and 6300. Engine coolant temperature is higher than 19o F at engine start. Engine coolant is higher than 68o F with the engine running after a warm restart.

Case Study: Misfire Monitor Diagnostic A vehicle is in your shop stall with DTC P0300, random misfires (FIGURE 7-17). The vehicle is currently running normally and use of the data list to view misfire counts shows no misfires currently. The technician then reviews the DTC freeze frame and notes that the ECT value at the time the DTC stored indicated 56o F. This indicates the engine was most likely operating during a cold start condition when the DTC set. This engine has direct injection (DI) and the vehicle has 38,491 miles.

FIGURE 7-17 Misfire DTC service information lists the possible causes for the condition. © Jones & Bartlett Learning.

Description The technician checks for any TSBs and finds one for DTC P0300 for this vehicle. The TSB recommends use of top-end cleaning using a liquid-based cleaning solution to remove deposits from the intake side of the intake valves and intake runners. This buildup can occur due to PCV blowby gases condensing and forming carbon-based deposits inside the intake and on the back of the intake valves. These deposits can cause lean misfire conditions during cold start. The technician follows the TSB for the top-end cleaning service and clears DTCs. The technician should recommend holding the vehicle for a final check and doing a cold start on the next business day, if the customer is able to leave the vehicle.

Fuel System Monitor 7-4 Diagnose fuel trim DTCs.

The fuel system is monitored continuously when the engine is running. When some technicians think of the fuel system, they may think of the fuel pump, fuel injectors, or other related components being monitored, but that is not what the ECM/PCM is monitoring. The PCM software has code written that includes a data map for fuel injector on-time. The on-time, sometimes referred to as injector duration, controls how much fuel is delivered to each cylinder. Increasing duration increases fuel delivery, creating a richer air-fuel ratio since the injector is ON longer, allowing more fuel into the cylinder. Decreasing duration creates a leaner air-fuel ratio. The injector duration is primarily controlled by the data map, but this data map may not create the best air-fuel ratio all the time. This is due to variations in fuel quality, ambient temperature, changing weather conditions (hot, dry air vs. wet, moist air during rain or snow), altitude changes, and variations in component tolerances. Fuel system engineers work with the PCM software engineers to allow for adjustments to the data map–based air-fuel ratios. This adjustment comes from the closed loop feedback of the oxygen or AF ratio sensor and is called fuel trim (FIGURE 7-18). The PCM uses the fuel data map to control injector on-time. When the vehicle is in closed loop control, the AF sensor (or oxygen sensor on older OBD II vehicles) provides a signal to the PCM that corresponds to the AF ratio for the combustion events that just occurred. The PCM uses these data to make adjustments to the injector ontime. If the target air-fuel ratio was 14.9:1 but the AF sensor indicates it was 15.2:1, that is too lean so the PCM increases injector on-time. If the AF sensor indicates 13.7:1, that is too rich, so the PCM reduces injector on-time. The PCM sets a target air-fuel ratio and the AF sensor provides the feedback for adjustments. Increasing injector on-time to correct a lean condition has the fuel trim moving away from 0% in a positive direction. Decreasing injector on-time to correct a rich condition has the fuel trim moving away from 0% in a negative direction.

FIGURE 7-18 Fuel trim data are displayed on the scan tool in percent for most vehicles. © Jones & Bartlett Learning.

Fuel Trim Fuel trim has two components: short term and long term. Both are displayed on the scan tool numerically as a percent (%) and may use the plus sign (+) to indicate an increase in injector duration and a minus sign (−) to indicate a reduction in injector duration (FIGURE 7-19). Short-term fuel trim data displayed on the scan tool shows how the PCM is making adjustments to fuel trim at that moment based on feedback from the AF sensor. You can view the AF sensor and short trim fuel PID data together on the scan tool to see this relationship operating.

FIGURE 7-19 Fuel trim includes short-term fuel trim and long-term fuel trim. The data are usually shown in a percent format on the scan tool. © Jones & Bartlett Learning.

Short-term fuel trim functions to pull or push the long-term fuel trim value away from 0%. For example, if the vehicle is running slightly leaner than normal due to a fuel filter that is nearing the end of its life, causing a slight reduction of fuel pressure, the lean signal from the AF sensor is dominant and pushes short-term fuel trim to a more positive value away from 0%. It increases until the AF sensor detects a slightly rich mixture and then it begins to cycle again with the AF sensor feedback. If short-term fuel trim remains at this higher value, let’s say around 7% for this example, long-term fuel trim readings begin to move positive away from 0%. Long-term fuel trim moves up to 1% and short-term fuel trim drops to 6%. If short-term fuel trim remains at 6%, long-term fuel trim moves up to 2% and short-term fuel trim drops to 5%. This continues until short-term fuel trim reaches the point where the AF sensor detects a slightly rich mixture and fuel control again can switch based on a target AF ratio and the short-term fuel trim commands are able to achieve this. In this case, due to a restricted fuel filter, long-term fuel trim moves to about 7%, allowing short-term fuel trim to cycle around 0% to make small corrections, positive and negative, based on the AF sensor feedback data values. Long-term fuel trim data are saved in the PCM keep alive memory (RAM), which is sometimes referred to as adaptive or learned fuel data management. This is done so that the ECM/PCM does not have to “relearn” the long-term fuel trim adjustment after every engine start. Short-term fuel trim is not stored after the ignition is turned OFF and resets to 0% at every engine start. Fuel trim is critical to diagnosing drivability concerns. Total fuel trim is

calculated by adding short- and long-term fuel trim for each bank together. Fuel trim is usually considered normal if it is +/– 6%. Using the data shown in FIGURE 7-20, add Bank 1 short-term and long-term values together (−0.8% + 12.5% = 11.7%) and Bank 2 (1.6% + 12.5% = 14.1%). The fuel trim data show that both Bank 1 and Bank 2 data are above the normal range and the PCM is increasing injector duration to compensate for a lean condition on both cylinder banks. The calculations show that the fuel trim data are exceeding normal limits and affecting both cylinder banks. AF ratio sensor feedback has indicated a lean condition that has deviated 11.7% for Bank 1 and 14.1% for Bank 2 from baseline data map injector duration values.

FIGURE 7-20 Fuel trim can be calculated by adding short-term and long-term fuel trim together for each cylinder bank. © Jones & Bartlett Learning.

Causes of Abnormal Fuel Trim Values Fuel trim may be affected by a lean or a rich condition. Lean conditions are caused when the amount of fuel injected into the cylinders is not sufficient for current engine conditions. Lower than normal fuel pressure can cause a P0171 too-lean DTC. Low fuel pressure may be caused by the following: Faulty fuel pump Clogged fuel filter Faulty fuel pressure regulator Kinked fuel line

Clogged fuel injector(s) Fuel line or injector fuel rail O-ring seal leaks Unmetered air entering the engine can cause a P0171 too lean DTC. This is sometimes called false air and can be caused by the following: Dirty or faulty MAF sensor Faulty MAP sensor (speed/density EFI systems) Dirty or clogged air filter Damaged/cracked air intake hose (between the MAF and throttle body) Leaking intake manifold gasket Warped plastic intake manifold Leaking injector to cylinder head O-rings Leaking exhaust manifold or manifold gasket A faulty precatalyst AF or oxygen sensor can cause a P0171 or a P0172 DTC because this sensor provides data on how well the air-fuel mixture burns in the cylinders. The P0172 DTC indicates the mixture is too rich and may be caused by the following: Faulty MAF sensor Faulty MAP sensor (speed/density systems) Faulty fuel pressure regulator (fuel pressure is too high) or fuel pump Leaky fuel injector(s) The fuel trim data and related too rich or too lean DTC help you begin to narrow your focus on what is causing the fault. A too rich or too lean fault immediately focuses you on either of the component lists. Engines with two cylinder banks have two sets of fuel trim data, one for each side of the engine (Bank 1 and Bank 2). The data from both banks can help you narrow the cause. For example, if both banks are too lean or too rich, then the cause is most likely a component that affects both cylinder banks, such as the MAF or fuel pump. It is unlikely that a faulty injector can affect both cylinder banks, as the fault would be isolated to the bank that the injector is mounted in. If only one bank has a fault, then focus on components that can only affect that bank, such as a faulty injector, AF sensor, or leaking exhaust manifold gasket.

Fuel Trim Diagnosis with a Smoke Machine The smoke machine is a great tool to assist in locating intake and exhaust system leaks (FIGURE 7-21). Intake system leaks after the MAF (or throttle body for MAP speed/density systems) create a lean condition that can lead to P0171. The smoke machine connected to the intake system can quickly locate leaks in the following:

FIGURE 7-21 A smoke machine is a great tool to isolate intake and exhaust leaks that can cause fuel trim DTCs. © Jones & Bartlett Learning.

Intake hose Intake manifold Vacuum lines Intake manifold to cylinder head seals/gaskets Fuel injector to cylinder head O-rings EGR valve gasket (if equipped) Connecting the smoke machine to the exhaust can locate an exhaust leak ahead of the AF or primary oxygen sensor (B1S1 or B2S1). This type of leak allows ambient air (rich in oxygen) to be pulled into the exhaust stream by the negative pressure between exhaust pulses of the cylinders. This oxygen fools the AF sensor into providing a too lean condition that does not actually exist; however, the PCM only reacts to the data available so it increases injector on-time. This type of fault can lead to reduced fuel economy, fouled spark plugs, and even catalyst damage due to the extra fuel. Evidence of smoke from the exhaust to cylinder head area, or a crack in the exhaust manifold, indicate that this is cause of the too lean fault. Repair the exhaust leak, then recheck fuel trim to verify whether this was the only fault, or continue diagnosis if readings are better but still not within the normal range of +/− 6%.

Fuel Trim Data Cells Fuel trim data are stored in cells (FIGURE 7-22). Each data cell relates to a small range of engine speed and load. You can verify this by viewing fuel trim data at idle. Increase the engine speed to about 2000 rpm and note that both values most likely changed instantly. This is because you are now in a different

fuel trim cell. Some scan tools display fuel trim data and include which fuel trim cell you are observing. Others display only short-term and long-term fuel trim for each cylinder bank. In this case, you can view the data in other cells by increasing engine rpm and engine load on the scan tool. You can do this during a test drive. Have another technician record the fuel trim data on the scan tool while you perform a fuel system drive cycle pattern (FIGURE 7-23).

FIGURE 7-22 Fuel trim data are stored in cells. The cells relate to a portion of the injector duration data map for that engine load condition. © Jones & Bartlett Learning.

FIGURE 7-23 A typical fuel system monitor drive cycle. © Jones & Bartlett Learning.

Description Fuel trim that exceeds the normal range limit will store a DTC. The DTC indicates which cylinder bank is affected and whether the fault is too lean or too rich (FIGURE 7-24). You can see there is a long list of causes for these DTCs.

FIGURE 7-24 Fuel trim DTCs set if the fuel system is too rich or too lean. © Jones & Bartlett Learning.

Description

Fuel Trim DTCs Values that exceed the threshold programmed into the ECM/PCM set a DTC, usually P0171 for too lean and P0172 for too rich. The DTC information usually provides information on the component or system causing the related condition (FIGURE 7-25).

FIGURE 7-25 Fuel trim values that exceed threshold limits set a DTC. © Jones & Bartlett Learning.

Description Fuel trim DTCs can store only if no other related DTCs are present (FIGURE 7-26). Systems that affect how efficiently the engine runs or sensors that directly relate to engine speed, engine load, and airfuel ratio will affect how the PCM attempts to adapt fuel injector duration. The presence of a PCMdetected fault does not allow the fuel system monitor to store a fuel trim DTC.

FIGURE 7-26 Fuel trim DTCs do not set if there is a fault in systems that affect engine control operation. © Jones & Bartlett Learning.

Description

TECHNICIAN TIP Do not make the assumption that all the components are okay and functioning normally if any of these DTCs are not stored and shown in the Enable Criteria list. For example, a contaminated MAF sensor hot wire can affect fuel trim data but may not set a DTC since MAF values have not exceeded DTC thresholds. The PCM is delivering fuel into the engine based on incorrect MAF data, and the AF sensor data lead to an out-of-range fuel trim value.

Diagnosing Fuel Trim DTCs A fuel trim DTC indicates that the ECM/PCM has exceeded the DTC threshold, and possibly a limit for injector on-time adjustment. The fault could be in the fuel system. Fuel pressure may be too high or too low. A fuel injector may be leaky or may have electronically failed. Many fuel trim DTCs are due to nonfuel system faults. Examples include: An air intake hose has cracked and allows unmetered air (air not measured by the MAF) to enter the engine. A leaking intake manifold gasket or a damaged fuel injector to manifold O-ring are other examples of how unmetered air can cause a fuel trim DTC. Exhaust manifold leaks ahead of the AF or HO2S can affect the data and cause a fuel trim DTC to set. Verify that the AF or HO2S has passed its related Mode 6 monitor and that the sensor functions to detect changes in fuel delivery using the related scan tool active test. Intake and exhaust leaks can often be isolated by performing a leak test with a smoke machine. Fuel pressure tests may be required to ensure fuel pressure is within specification. Because fuel trim DTCs are caused by faults in other systems, they can be a challenge to diagnose. However, the DTC diagnostics list the possible causes for a lean or rich fuel trim DTC. Verify that there are no intake or exhaust leaks. Verify sensor inputs related to accurate fuel delivery are okay or out of range. Some auxiliary emission systems, such as EGR, EVAP, and secondary air, can cause a fuel trim–related DTC. Examples include an EGR valve that allows exhaust gas to dilute the air-fuel mixture at all times, an EVAP purge valve ON at all times, or a secondary air system pump that remains ON after closed loop fuel control begins. To perform fuel trim diagnosis, follow the steps in SKILL DRILL 7-3. TECHNICIAN TIP Clear DTCs only after you have diagnosed the cause of the fuel system DTC. Clearing DTCs may reset the long-term fuel trim to 0% and usually erases any freeze frame and Mode 6 test data. Once the DTC fault is isolated and then repaired, erase DTCs and perform the fuel trim DTC drive cycle to verify that fuel trim is now within normal levels.

SKILL DRILL 7-3 Diagnosing Fuel Trim 1. When a vehicle comes into your repair facility with a fuel trim lean or fuel trim rich DTC there are some basic items that need to be checked before getting into heavy diagnostics. 2. Using a scan tool, verify the DTC in the PCM is a fuel trim DTC. 3. The next step is to check TSBs for reprogramming information or a common failure. Like other systems, common failures could be caused by a software issue that the OEM has found and repaired with an updated program. Always check TSBs before any repairs.

Basic inspection of the vehicle in your bay should start underneath the hood. Verify the snorkel is in serviceable condition, 4.

verify all of the hoses and vacuum lines are hooked up properly before continuing. If a hose is found to have a tear in it or it was disconnected, repair that issue and then reevaluate the code.

5. If all of the hoses underneath the hood are in serviceable condition, then the next step is to move to the HO2 sensors. Raise the vehicle and then inspect the exhaust system for leaks. Pay close attention to the area around the HO2 sensors because those sensors are the main ones that help determine fuel trim. 6. If underhood and exhaust system inspections reveal no major failures, use the scan tool to operate the vehicle within the freeze frame parameters and see if the engine goes extremely lean or extremely rich. Excessive fuel trims are generally +/ − 10% on either side of the engine at one time, and the STFT should be less than +/− 3%. 7. If the STFT is out of range, determine whether it is adding or subtracting fuel. It is opposite of what the STFT is doing as the PCM is trying to correct the condition. For example, if the STFT says +10%, it means it is extremely lean and the PCM is trying to richen it up, and the opposite is also true. In a lean situation the technician should be looking for low fuel volume, stuck HO2, or a vacuum leak. In a rich condition (–10% STFT) the technician should be looking for a leaking fuel injector or stuck HO2. 8. Most DTCs related to this situation will walk you through these steps, as you work through the DTC flow chart to determine the failure pertaining to the exact vehicle in your bay. This is meant as a general guide that most technicians follow.

Case Study: Fuel Trim Diagnostic A vehicle is in for a check engine light on concern. The technician reads DTC P0171 on the scan tool, system too lean. There are many causes for this concern, as shown in FIGURE 7-27, including intakerelated false air leaks, which are air leaks that allow air into the intake system that is not measured by the MAF sensor and low fuel pressure, which could be caused by a failing fuel pump.

FIGURE 7-27 System too lean DTC lists possible causes for the condition. © Jones & Bartlett Learning.

Description The DTC diagnostic procedure in the service information begins with a question: Are any other DTCs stored (FIGURE 7-28)? If yes, then the technician must diagnose those first, as the fault related to the other DTC(s) could be the cause of the lean condition (e.g., a fault in the air-fuel ratio sensor). The technician verifies there are no other DTCs. While it is not listed as part of the diagnostics, understanding of fuel trim is implied in most cases with respect to the DTC diagnostic procedure. It is good practice to view the scan tool fuel trim live data and view what the fuel trim readings are for various engine conditions.

FIGURE 7-28 DTC P0171 diagnostics are designed around the most likely to the least likely cause of the concern. © Jones & Bartlett Learning.

Your knowledge can save you time. For example, this case study vehicle has fuel trim numbers that increase as engine speed and load increase. Note that the diagnostic procedure begins with the PCV and air intake inspection. A fault with either of these would cause fuel trim to be very high at idle but decrease as engine rpm and load increase. Therefore, it is unlikely that this vehicle has a false air concern. Below normal fuel pressure could cause the concern on our case study vehicle, causing the fuel trim numbers to increase as engine speed and load increase. The lack of adequate fuel pressure at engine idle may not be enough to cause fuel trim to adjust much; however, as the engine speed and load increase, there is not enough fuel injector on-time for a proper air-fuel mixture, and fuel trim moves positive to compensate (injector on-time is increased). Strategy-based diagnostics are not solely focused on following the service information step by step. They encourage you to use your knowledge of system operation to focus on the conditions of the vehicle you are working on; then based on this information, you should feel confident to begin with the diagnostic

step that is most likely to apply to the vehicle in your shop stall (FIGURE 7-29). The technician notes that fuel pressure is 33 psi at idle and drops to 27 psi when raising engine rpm to 2500 (FIGURE 7-30). This is below the specification of 44 to 50 psi. The technician can now focus on the fuel delivery system to isolate the cause and then repair the vehicle. The technician performs a fuel pump current test using a DSO and notes an abnormal pattern. The fuel pump motor is worn and the fuel pump assembly must be replaced. After installing a new pump unit, the fuel trim and fuel pressure are rechecked. Fuel pressure is 49 psi under all conditions and fuel trim is now moving negative, returning to normal (FIGURE 7-31). The technician clears DTCs, which resets fuel trim, and then performs a thorough test drive to verify critical monitors for the air-fuel ratio sensor and catalyst complete and pass. The technician can now complete the repair order and return the vehicle to the customer with confidence that the repair has eliminated the cause of the concern.

FIGURE 7-29 Diagnostic steps like a fuel pressure inspection and any exhaust leaks ahead of the AF sensor are usually included as part of the strategy-based diagnostic process. © Jones & Bartlett Learning.

Description

FIGURE 7-30 Fuel pressure is 33 psi at idle and drops to 27 psi when raising engine rpm to 2500. These pressures are below normal and require fuel system diagnosis. © Jones & Bartlett Learning.

FIGURE 7-31 After replacing the faulty fuel pump, fuel pressure is 49 PSI under all conditions. Fuel trim data show the PCM is now able to reduce fuel trim (injector on-time). Over a short period of time, the fuel trim returns to normal limits. The technician

can now clear the DTC and the MIL will turn off. © Jones & Bartlett Learning.

WRAP-UP Ready for Review The OBD II continuous monitors operate every time the key is in the run position. Monitors are used by the PCM to determine how the engine is operating on the vehicle and whether it is meeting the emission goals for that year of vehicle. Component monitors evaluate the operation of different components on the engine to determine whether they are operating correctly. Misfire monitors are used to determine if there is a failure within a particular cylinder. The misfire monitor is used to help the technician determine which cylinder is failing at that time. Short-term fuel trim explains what the PCM is trying to do with the engine to help it meet performance goals in a quick, short-term fashion. Long-term fuel trim explains what the PCM is projecting the fuel trim will be in the future. Fuel trims can be used by the technician to help diagnose fuel issues and other issues the PCM is trying to correct. Abnormal fuel trims can be caused by vacuum leaks, fuel leaks, and possible sensor failures. Once a DTC is triggered by a failed monitor, subsequent monitors may not operate until the failure is fixed.

Key Terms Component monitor An OBD II test run to ensure that a specific component or system is working properly. Continuous monitors OBD II monitors that run continuously throughout the drive cycle. Data map The preprogrammed operational strategy of the PCM. Enabling conditions The operation conditions required before a monitor is allowed to run. Fuel trim The fueling strategy that is used by the PCM. Injector duration The amount of time (usually in ms) the injector is switched ON. Long-term fuel trim Calculated by the PCM based on how the engine is operating currently, it directs long-term engine operation. Misfire monitor An OBD II test that monitors engine misfires and alerts the driver if there is a misfire. Monitor description An explanation of what the monitor is watching and what it is looking for. Parameter ID (PID) Used to identify each value that is monitored by the PCM. Short-term fuel trim A calculation that determines the amount of fuel the engine is using and adjusts based on the upstream oxygen sensor signal.

Review Questions 1. Review the DTC enabling criteria shown in the diagram below. All of the following allow the monitor to run EXCEPT: a. DTC P0340. b. closed loop. c. battery voltage is 13.9. d. engine load is 27.7%.

© Jones & Bartlett Learning.

2. The total fuel trim for Bank 1 of this vehicle is which of the following? a. −1% b. −16% c. −17% d. −10%

© Jones & Bartlett Learning.

3. The misfire monitor critical sensors include the CKP and which of the following? a. AF sensor b. HO2S c. MAF d. CMP 4. All of the following have their data reviewed by the component monitor EXCEPT: a. AF sensor. b. CKP. c. ECT. d. MAF. 5. A leaky fuel injector in Cylinder 3, located in Bank 2, will cause which of the following? a. Bank 2 short-term fuel trim to move positive and long-term to move negative b. Bank 1 short-term fuel trim to move negative c. Bank 1 long-term fuel trim to move positive d. Bank 2 short-term and long-term to move negative 6. The fuel trim data are stored in __________ that relate to engine speed and load. a. cubes b. pages c. cells d. bunkers 7. All of the following can cause the ECT component monitor to store a DTC EXCEPT: a. a broken wire that creates an open sensor circuit. b. 400 Ω resistance in the ECT sensor ground wire. c. a short to ground on the ECT signal wire. d. the ECT sensor connector disconnected. 8. All of the following can cause fuel trim numbers to move positive EXCEPT: a. an open MAF circuit. b. a cracked intake air hose. c. a clogged fuel injector. d. low fuel pressure. 9. A failed exhaust manifold gasket or exhaust manifold leak at the cylinder head can cause fuel trim to adjust as which of the following? a. Short-term and long-term values decrease. b. Short-term and long-term values increase. c. Only long-term values decrease. d. This will have no effect on fuel trim because it is unrelated to the monitor. 10. All of the following will cause the component monitor to set a DTC and illuminate the MIL EXCEPT: a. an open circuit to the VVT solenoid. b. an open IAT signal wire. c. a Cylinder 2 ignition coil arcing to ground. d. an open knock sensor circuit.

ASE Technician A/Technician B Style Questions 1. Technician A says negative fuel trim indicates fuel injector pulse width is increasing. Technician B says short-term and long-term fuel trim values are within normal range if when added together they are +/− 6%. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B 2. Refer to the scan tool screen shot shown below. Technician A says that there are several fuel trim cells and these data apply to all of them. Technician B says that that this vehicle is running lean. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B

© Jones & Bartlett Learning.

3. Refer to the misfire service information shown below. Technician A says that misfire DTCs set a pending DTC on the first trip a misfire is detected. Technician B says a severe misfire will cause the MIL to blink on the first trip it is detected. Who is correct? a. Technician A b. Technician B

c. Both Technician A and Technician B d. Neither Technician A nor Technician B

© Jones & Bartlett Learning.

4. Refer to the component monitor service information shown below. Technician A says the MIL illuminates as soon as a fault is detected. Technician B says this DTC determines if sensor data are valid for current engine conditions. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B

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5. Technician A says this DTC cannot store immediately after engine start. Technician B says this DTC will not set if the engine is cold. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B

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6. Technician A says a fuel trim DTC will not store if there is a DTC for AF ratio heater circuit failed open. Technician B says a fuel trim DTC will not store if there is a MAF or MAP sensor circuit fault. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B 7. Technician A says the malfunction threshold of 0.17 V indicates that there may be an open circuit on the sensor ground wiring. Technician B says the malfunction threshold of 4.91 V indicates that there may be a short circuit on the IAT signal wiring. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B

© Jones & Bartlett Learning.

8. Technician A says the component monitor covers AF and HO2S DTCs. Technician B says all component monitor input sensors and output actuators can store a DTC with the ignition ON, engine OFF (KOEO). Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B 9. Refer to the VVT enabling conditions shown below. Technician A says this monitor will run even if other system DTCs are stored. Technician B says the engine does not have to be running for this DTC to store. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B

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10. Refer to the monitor strategy shown below. Technician A says this monitor functions once per driving cycle. Technician B says this system is part of the continuous component monitor. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B

© Jones & Bartlett Learning.

© Jones & Bartlett Learning.

CHAPTER 8

Noncontinuous Monitors: Oxygen Sensor and Secondary Air Monitor Operation and Diagnosis LEARNING OBJECTIVES After studying this chapter, you should be able to: 8-1

Explain the operation of the heated oxygen sensor.

8-2

Diagnose oxygen sensor heater circuit concerns.

8-3

Diagnose zirconia (narrow-band) oxygen sensors.

8-4

Explain the operation of the heated air-fuel ratio sensor.

8-5

Diagnose air-fuel ratio (wide-band oxygen) sensors.

8-6

Diagnose secondary air system concerns.

YOU ARE THE AUTOMOTIVE TECHNICIAN A check engine light concern leads you, the technician, to DTC P0136 oxygen sensor. Which of the following will most likely be required for your diagnosis? View KOER data list parameters. Review DTC-related service information. View OBD II Mode 5 data. View OBD II Mode 6 data. Review freeze frame data. View fuel trim data. Perform MAP and/or MAF inspection and related testing. Check for an exhaust leak. Perform HO2S or air-fuel (AF) ratio sensor tests. Verify proper fuel pressure.

Diagnostic trouble code (DTC) diagnosis planning is made using step 2 of the strategy-based diagnostic process. This includes using the service information DTC diagnostics, which detail the related noncontinuous monitor operation, component descriptions, and possible system faults. This chapter prepares you for the inspection and testing procedures you will perform when diagnosing the oxygen sensor (along with the AF ratio sensor and secondary air system).

Introduction OBD II monitors vehicle engine and transmission performance and is designed to illuminate the check engine light when a malfunction occurs that will affect vehicle emissions levels 8% beyond normal limits. Some systems are monitored continuously, meaning they are monitored at all times when the engine is running. Other systems are monitored when specific enable criteria are met. This chapter covers the following noncontinuously monitored systems: Oxygen sensor and sensor heater Air-fuel ratio sensor and sensor heater Secondary air system

OBD II Heated Oxygen Sensor Operation 8-1 Explain the operation of the heated oxygen sensor.

The oxygen sensor functions to detect exhaust gas oxygen levels (FIGURE 8-1). The ideal air-fuel ratio is 14.7 to 1 and is called the stoichiometric air-fuel ratio. This ratio allows the oxygen to mix with fuel vapors for complete conversion of hydrocarbon (HC)–based fuel and air during the combustion process into carbon dioxide and water. The simplified chemical equation for the gasoline-powered internal combustion engine is HC + O2 = CO2 + H2O. Of course, the actual formula is much more complex for two reasons. The first is that gasoline is a complex molecule comprising a chain of hydrogen and carbon atoms, along with additives to promote cleaner fuel combustion and the reduction of engine deposits. The second reason is that the combustion process is never perfect. For this reason, there are other emissions gases, including carbon monoxide (CO), oxides of nitrogen (NOx), and unburned fuel (HC), which exit the cylinder during the exhaust stroke. The oxygen sensor reacts to oxygen levels only in the exhaust gases, not in any of the other gases present.

FIGURE 8-1 The heated oxygen sensor is usually identified by a four-wire connector. © Jones & Bartlett Learning.

The oxygen sensor generates a voltage signal that is used by the PCM to determine whether the amount of fuel delivered into the cylinders (injector on-time) resulted in a rich or a lean mixture. The PCM adjusts the injector on-time in response to the oxygen sensor voltage signal. This adjustment is called fuel trim and can be observed on the scan tool PID data. The oxygen sensor generates a voltage using two zirconia-plated elements. The first element is in the center area of the sensor and is exposed to ambient air (FIGURE 8-2). The ambient air enters the reference chamber and is heated by the sensor heater and the vehicle exhaust. The oxygen sensor must reach approximately 600o F to operate. Heating the oxygen to this temperature is what allows it to react with the zirconia elements and create a voltage. The oxygen sensor operates similar to a battery. The zirconia elements are basically electrodes that react to oxygen levels. A voltage is created when there is a difference in the number of electrons between two points. In this case, the two points are the reference chamber and the outer chamber, which is in the exhaust stream. The reference chamber oxygen level is stable. As the exhaust oxygen levels change with rich or lean mixtures, there is a difference in electrons between the exhaust electrode and the reference electrode. This difference in electron levels generates a small voltage of between 0.1 V during a lean mixture and 0.9 V during a rich mixture (FIGURE 8-3).

FIGURE 8-2 The oxygen sensor outputs a voltage signal and operates similar to a battery. © Jones & Bartlett Learning.

Description

FIGURE 8-3 The difference in electrons from oxygen atom amounts creates a voltage that is used by the PCM to determine what type of fuel trim adjustment needs to be made. © Jones & Bartlett Learning.

Description During a lean mixture, there is less fuel for the oxygen that is present in the combustion chamber; therefore, some of the oxygen is not consumed during the fuel burning event and is still present in the exhaust. Since oxygen is present in the exhaust and in the reference chamber, there is a smaller difference between the two oxygen zirconia elements, resulting in a small output voltage between 0.1 and 0.3 V. Again, voltage is related to the difference in electron count between the two electrodes. During a rich mixture, there is more fuel for the available oxygen present in the combustion chamber. During the burn process, almost all the oxygen is consumed. This results in almost no oxygen present in the exhaust stream and a high difference in the electron count between the two electrodes, resulting in a high voltage of about 0.9 V from the sensor. Generally, 0.7 to 0.9 V indicate a rich mixture and 0.1 to 0.3 V indicate a lean mixture. The ideal mixture (stoichiometric) results in an oxygen sensor output of 0.45 V. It is important to note that the oxygen sensor can detect only whether the air-fuel mixture is lean or rich. It cannot detect how rich or lean the mixture is. That is why the oxygen sensor has been replaced by the air-fuel ratio sensor for most applications. The primary oxygen sensor for fuel system feedback is located ahead of the catalyst and is named sensor 1 (S1) as shown in service information and on the scan tool data list PIDS. The sensor after the catalyst is called sensor 2 (S2). An inline engine has one cylinder bank, so it will usually have heated oxygen sensor Bank 1 (HO2S1B1) and another after the catalyst, HO2S2B1. A V-type engine will have Bank 1 and Bank 2 sensors (FIGURE 8-4). Bank 1 is usually on the engine side that has cylinder 1, but this is not always the case. Verify using the service information if you are not sure. Also, some vehicles that use air-fuel ratio sensors ahead of the catalyst(s) may use an oxygen sensor(s) after the catalyst.

FIGURE 8-4 OBD II vehicles may have oxygen sensors located before and after the catalyst. Pre-CAT oxygen sensors are called precatalytic converter sensors, and those after the catalytic converter are called post-CAT sensors. © Jones & Bartlett Learning.

OBD II Oxygen Sensor Heater Circuit Analysis 8-2 Diagnose oxygen sensor heater circuit concerns.

Oxygen sensors on OBD II vehicles use an integrated oxygen sensor heater. The heater functions to bring the oxygen sensor up to operating temperature (600o F) as quickly as possible. Some vehicles also use a secondary air system to heat the sensor quickly to operating temperature. This allows the PCM to enter closed loop fuel control as quickly as possible, which reduces emissions and improves fuel efficiency, usually in 30 to 60 seconds under moderate ambient temperature conditions. The PCM controls the path to ground for the sensor. The heater is usually active at all times when the ignition is ON. The PCM operates the heater circuit and monitors circuit current to determine whether the circuit has an open, short, or excessive resistance. Some manufacturers monitor the sensor heater when the engine is running and enable criteria are met (FIGURE 8-5).

FIGURE 8-5 A sample of oxygen sensor heater monitor enabled criteria found in the service information.

© Jones & Bartlett Learning.

Description A few manufacturers test the oxygen sensor heater after the engine is shut OFF and a certain amount of time has passed. In either case, the test results can be viewed as part of the Mode 6 test results (FIGURE 8-6).

FIGURE 8-6 OBD II Mode 6 shows the oxygen sensor heater monitor test results. The data are used to help you determine the cause of the fault and also after your repair is made. © Jones & Bartlett Learning.

Use the Mode 6 test result data to assist in your diagnosis. For example, do the data indicate an open circuit (current value is too low) or a short circuit (current level is too high)? This will help you plan your circuit and component testing as you use the related DTC diagnostics in the service information. Oxygen sensor heater circuit testing usually involves the following tests: Measure resistance of the sensor heater and verify whether it is within normal limits. Most sensor heater elements fail open and show a value of OL on the DMM. A shorted element is indicated by a very low ohms reading (close to 0 Ω). Verify correct voltage is present on the source and ground of the circuit at the sensor. Measure resistance or voltage drop of the sensor heater wiring. Voltage drop is the better test

because the circuit is ON during your test. The voltage drop should be less than 0.5 V. Repairs include replacing a failed sensor (the heater is part of the sensor and not serviceable), harness repairs, and in rare cases a failed PCM. The final step of the strategy-based diagnostic process is to verify your repair. It is critical that you perform the applicable drive cycle for the oxygen sensor heater circuit and verify that the Mode 6 data indicate the heater is functioning normally. Also, since this DTC most likely prevented other monitor tests from running, it is prudent to verify that fuel trim is within normal limits and that the related oxygen sensor monitor has run and passed. Failure to do this can lead to a comeback based on the MIL turning ON. To the customer, the MIL ON is a repeat of the same fault, even though it may now be due to a different component. You can avoid this by completing all relevant monitors. If you find a new fault, you must then diagnose and repair that fault (once the customer approves the additional work) and then repeat this final process again. To test the oxygen sensor heater, follow the steps in SKILL DRILL 8-1.

Testing Heated Oxygen Sensor 8-3 Diagnose zirconia (narrow-band) oxygen sensors.

The heated oxygen sensor(s) on the vehicle is monitored at the appropriate time during the drive cycle when enable criteria are met. The oxygen sensor output is monitored for voltage amplitude and response time to verify that the sensor is providing accurate data for fuel trim control. SKILL DRILL 8-1 Testing the Oxygen Sensor Heater 1. Obtain the oxygen sensor heater service information, including DTC diagnostics and related wiring diagram for your assigned vehicle. 2. Connect a scan tool to your vehicle and access the Monitor Test results (Mode 6) for the oxygen sensor heater. Compare the results with the limits shown on the scan tool or in the service information and note whether the results are within or outside the normal range. Tech Note: An incomplete monitor test may not have any test results present.

3. Follow the related diagnostics for your vehicle to complete the following (the order may vary based on the service

procedure for your vehicle): a. View the oxygen sensor heater current value on the scan tool PID data (Mode 1) and note whether the value is within the normal range. b. Follow the procedure to measure the resistance value of the oxygen sensor heater using a DMM.

TECHNICIAN TIP The oxygen sensor wiring from the sensor to its harness connector is often generic, meaning that the sensor is used for many different applications on various vehicles. The wiring diagram wire color may not be the same on the harness that directly attaches to the oxygen sensor. Use the vehicle wiring harness side of the oxygen sensor connector to locate the correct wire and connector for testing based on wire insulation color and pin location in the connector. Compare your results to the service specification and note whether the sensor heater resistance is okay or out of range.

c. Measure the continuity value of the wiring between the oxygen sensor heater source and ground from the PCM to the oxygen sensor connector. Note your results and whether they are within specification (very close to 0 Ω). 4. Review your oxygen sensor heater test findings with your instructor. 5. Return the vehicle to normal condition and clear any DTCs that may have stored from your work. Return test equipment and tools to their storage location.

© Jones & Bartlett Learning

The amplitude refers to the oxygen sensor reacting to lean and rich conditions with voltages that reflect those conditions (FIGURE 8-7). The PCM monitors that the amplitude goes high enough during a rich condition and low enough during a lean condition. If the amplitude is not low or high enough, the monitor fails the test and a DTC stores when the failure repeats on two consecutive drive cycles. This

test is checking for biased lean or rich oxygen sensor voltages. A biased lean voltage is always lower than normal as it reacts to rich and lean conditions. A biased rich voltage is always higher than normal at it reacts to rich and lean conditions.

FIGURE 8-7 Oxygen sensor scope pattern with lean or rich bias (voltage never reaches above 0.7 V for lean bias and never goes below 0.25 V for rich bias). © Jones & Bartlett Learning.

TECHNICIAN TIP Two-trip DTCs operate as follows: The first failed trip of a monitored component or system stores monitor test results in Mode 6, but the monitor status remains incomplete. If the monitored component or system fails on the next trip, a DTC and freeze frame stores, and the monitor status changes to complete and shows that the test failed (Mode 6 test results).

The oxygen sensor is also tested for reaction time. A responsive oxygen sensor reacts to a changing air-fuel ratio from lean to rich or rich to lean in less than 100 milliseconds (ms). A sensor that takes longer than 100 ms is considered lazy and will allow emissions levels to increase above normal limits. The PCM checks for reaction time by changing the air-fuel ratio to a defined rich or lean condition and then monitors the amount of time it takes for the oxygen sensor voltage to increase for a forced rich condition or decrease for a forced lean condition. A sensor that fails the test on two consecutive drive cycles stores a DTC, and the test results are stored under the monitor test results. Diagnosing an oxygen sensor voltage or switch time fault is not difficult and requires use of a digital

storage oscilloscope (DSO) (FIGURE 8-8). To practice testing the heated oxygen sensor for reaction to lean and rich mixtures and switch time from a lean to rich condition, follow the steps in SKILL DRILL 8-2.

FIGURE 8-8 Oxygen sensor output voltage and switch times can be verified using a DSO. Using this visual image helps the technician determine whether the sensor is faulty or whether it is being affected by an outside entity. Courtesy of Pico Technology Ltd.

TECHNICIAN TIP The oxygen sensor signal output can be affected by an exhaust leak ahead of the sensor. A sensor that passes the reaction tests but has a related DTC or if fuel trim is too lean, check for an exhaust leak. You can use a smoke-generating machine for this test. Connect the machine’s smoke output hose to the exhaust pipe and then determine whether there is a leak ahead of the oxygen sensor(s). Repair any leaks found. Recheck oxygen sensor operation. If okay, perform a test drive to run the oxygen sensor test and verify that it completes and passes.

Heated Air-Fuel Ratio Sensor Operation 8-4 Explain the operation of the heated air-fuel ratio sensor.

The wideband air-fuel (AF) ratio sensor appears very similar to the oxygen sensor (FIGURE 8-9). The AF sensor does not operate like the oxygen sensor. There have been different types of AF sensors used among the various manufacturers, so this text covers the fundamental operation of an AF sensor and the general diagnostics procedures. The AF ratio sensor began to appear on vehicles in the late 1990s. Some use four wires, some five, and some seven wires or more. This section focuses on the four-wire type, although others function in a similar manner (FIGURE 8-10).

FIGURE 8-9 The wideband air-fuel ratio sensor looks similar to an oxygen sensor. It may have four, five, or more wires depending on manufacturer and type. © Jones & Bartlett Learning.

FIGURE 8-10 The AF sensor is designed around a circuit that reacts to very small changes in the amount of oxygen in the exhaust. © Jones & Bartlett Learning.

Description SKILL DRILL 8-2 Using a DSO for Zirconia Oxygen Sensor Diagnosis

1. Access the related service information and identify the signal wire for the oxygen sensor. Note that the oxygen sensor wiring from the sensor to the harness connector is often generic and may not have the same wire color code as indicated on the wiring diagram. Be sure to look at the wiring harness that goes back to the PCM for the correct color coding.

2. Connect the DSO signal lead to the oxygen sensor signal wire. Connect the DSO ground lead to the oxygen sensor signal ground.

3. Start the engine and note the sensor values as it warms up.

4. The first test is to see whether the sensor reacts to a lean condition. Do this by creating a small vacuum leak by removing a small-diameter vacuum line. This creates a lean condition, and the oxygen sensor voltage should go very close to 0 V and hold until the fuel trim adjusts for the vacuum leak. If the sensor passes this test, continue to the next test.

5. Create a rich condition by spraying a small amount of throttle body cleaner into the disconnected vacuum port or connect a propane bottle to the port. The oxygen sensor voltage should go above 0.8 V during this test. If the sensor passes this test, continue to the next test.

For the next test, measure oxygen sensor reaction time. Reconnect the vacuum line and let the fuel trim readjust so the 6. sensor is switching between rich and lean conditions. Disconnect the vacuum hose again and then freeze the DSO display to measure the switch time reaction to the lean condition. It must be less than 100 ms. Most good sensors will switch in less than 10 ms. The second part of this test is to measure switching to a rich condition. Reconnect the vacuum hose and let the fuel trim readjust so the oxygen sensor is switching again normally. Remove the vacuum hose and quickly spray a very small amount of throttle body cleaner into it. Once the oxygen sensor reacts to the rich condition, freeze the screen and measure the switch time. Again, it must be less than 100 ms.

7. Replace the oxygen sensor that fails any of the tests for voltage amplitude or switch time. A sensor that appears to switch but has a shallow amplitude is biased. A lean biased sensor usually remains below 0.5 V, and a rich biased sensor usually remains above 0.4 V. Be sure to install the correct oxygen sensor for the vehicle application. It is good practice to repeat the oxygen sensor tests on the new sensor and be sure to perform a test drive to run the monitor test until they complete. A faulty oxygen sensor can lead to temporary or permanent damage to the catalytic converter(s). An oxygen sensor fault will halt running the catalyst monitor. Installing a new sensor that passes its monitor will then allow the catalyst monitor to run. If you do not verify the monitors have run and passed, the customer will do so as they drive and could lead to a malfunction indicator lamp (MIL) ON comeback situation. © Jones & Bartlett Learning

Let’s review the key terms related to air-fuel ratio. The stoichiometric, or ideal air-fuel ratio, is 14.7 parts of air (oxygen) to 1 part of fuel (hydrocarbons [HC]). Modern engines are actually able to run at leaner air-fuel ratios through the use of an air-fuel ratio sensor. This reduces emissions and increases

fuel economy. The air-fuel ratio is usually described using the lambda scale, where the stoichiometric ratio has a value of 1 on the lambda scale. Values that are lower than 1 indicate a richer mixture. Values higher than 1 indicate a leaner air-fuel ratio. This is important for the advanced engine performance technician to know, as the air-fuel lambda value is shown on the scan tool and you will need to interpret this data during your diagnosis of air-fuel ratio sensors. Unlike the oxygen sensor where it only detects that the exhaust gas indicates a rich or a lean mixture, the air-fuel ratio sensor can detect the actual air-fuel ratio. The sensor is able to do this by monitoring sensor current. Remember that an oxygen sensor uses the difference in oxygen levels between ambient air and the amount of oxygen in the exhaust gasses. The reaction between the difference in the oxygen levels creates potential voltage difference in the oxygen sensor’s signal output, with a voltage below 0.35 V indicating a lean condition and above 0.55 V a rich condition. Again, the oxygen sensor indicates the lean or rich condition only, not the actual lambda value. The AF sensor can provide the actual lambda value by using a reference voltage and current based on the stoichiometric ratio (FIGURE 8-11). The AF sensor example shown is similar to most; however, the voltage and current values can vary between sensor types and manufacturer designs. A lambda of 1 is indicated when the current is 0 amps and has a voltage of 3.30 V.

FIGURE 8-11 The AF sensor current is positive during a lean condition and negative during a rich condition. © Jones & Bartlett Learning.

Description The AF sensor uses a diffusion chamber. This is how an oxygen sensor differs from an air-fuel ratio sensor. It is sometimes described as an oxygen sensor within an oxygen sensor, although this is a simplification. What is important is that you understand AF sensor operation as follows:

The PCM supplies voltage to the AF sensor electrodes. The examples shown of Figure 8-10 are 2.9 V and 3.3 V. This AF sensor generates 0.40 V when the air-fuel ratio is 14.7:1. This voltage is in addition to the 2.9-V constant that the PCM provides. There is now 3.3 V on both electrodes. Therefore, there is 0.0 amperes of current in the circuit since both electrodes are equal in value. Another way to state this is that there is no potential difference between the two electrodes. Think of a totally discharged battery. It has no electron difference between the positive and negative posts, so it has 0 V. Electrons cannot flow in any circuit connected to a discharged battery since there is no voltage present. The AF sensor operates on these same principles. This sensor will have 0 V and 0.00 amps of current when the air-fuel ration is 14.7:1. You can usually view these values on the scan tool PID data (Mode 1). During a lean condition, there is an excess level of oxygen molecules in the exhaust so the AF sensor pumps oxygen ions into the reference cell to keep the level of ions balanced. This results in an increase in voltage on the 2.9-V electrode. There is now a potential difference between the two electrodes and current is now present in a positive direction. During a rich condition there is an excess of oxygen molecules in the exhaust so oxygen molecules must now be pumped in the opposite direction. This results in a voltage decrease below 2.9 V and the current is a negative value because the electrons are moving in the opposite direction. The AF sensor can detect the actual lambda value as it functions to balance the oxygen ions between the chambers. Lambda is the method to represent the air-fuel ratio. The scale uses the number 1 to represent the stoichiometric air-fuel ratio of 14.7 parts air to 1 part of fuel. The number 14.7 comes from the weight of air at sea level, 14.7 pounds per square inch. Numbers less than 1 have more fuel and indicate a richer mixture. Numbers higher than 1 have less fuel and represent a leaner mixture. A lambda value of 0.93 is rich, and a value of 1.08 is lean. Many manufacturers display the lambda value as part of the PID data on the scan tool. The PCM software sets a target air-fuel ratio using a lambda value and the A/F sensor signal is processed and displayed as the actual AF ratio. The PCM then adjusts fuel trim to increase or decrease injector on-time from the base fuel map to meet the target AF ratio. The movement of the oxygen ions alters the balance around the values when lambda is 1 (stoichiometric). The current value is used by the PCM and compared to a lookup table value that equates to the related lambda values. This example has a voltage value of 2.9 V and a current of 0 amperes at a lambda of 1 (FIGURE 8-12).

FIGURE 8-12 The example AF sensor has a voltage and current increase as the lambda moves leaner. © Jones & Bartlett Learning.

Description

Air-Fuel Ratio Heater Circuit Testing 8-5 Diagnose air-fuel ratio (wide-band oxygen) sensors.

Most gasoline internal combustion engine (ICE) OBD II vehicles use an AF ratio sensor before the catalyst (FIGURE 8-13). An oxygen sensor or an air-fuel ratio sensor may be used after the catalyst.

FIGURE 8-13 Air-fuel ratio sensors are now the most common type used in the exhaust ahead of the primary catalyst. © Jones & Bartlett Learning.

Description Inline engines use the identifier of Bank 1 S1 to indicate the sensor ahead of the catalyst and Bank 1 S1 to identify the sensor after the primary catalyst (FIGURE 8-14). Bank 2 identifies the sensors on the other side of the engine. Always refer to the service information to properly identify the location of the sensor you are diagnosing.

FIGURE 8-14 The Bank 1 sensors are usually on the cylinder 1 side of a V-type engine. © Jones & Bartlett Learning.

Description Oxygen sensors begin to function at temperatures of 600o F; however, air-fuel ratio sensors must reach 1200o F. These sensors use a built-in heater to bring them up to operating temperature quickly so the PCM can enter the closed loop fuel control for minimal exhaust emissions and improved fuel efficiency. The PCM usually regulates heater temperature and current using duty cycle voltage control. This is especially important for air-fuel ratio sensors due to the high temperature they require to operate. Moisture can condense on the sensor overnight. Operating the sensor heater at full voltage during a cold engine start condition could cause the ceramic element in the sensor to shatter due to rapid and uneven heating. The PCM duty-cycles voltage to the heater allowing it to regulate the heater so that there is no damage to the sensor components. A failed heater or problem with the heater circuit can delay or totally impede sensor operation, which increases emissions levels and reduces fuel efficiency. The PCM monitors current level of the sensor heater circuit. Most sensor failures are due to a damaged or failed heater element creating an open circuit so the current level falls to 0 amps. Damaged wiring or a heater element that shorts to ground increases current outside the normal range. This condition could also damage the related circuit in the PCM, requiring that it be replaced along with the damaged sensor. Resistance in the wiring impedes current to below normal levels. All of these conditions set a DTC. The sensor heater monitor uses twotrip detection logic. A failure on the first trip sets a preliminary DTC and the malfunction indicator lamp (MIL) remains OFF. A consecutive trip failure sets a DTC and the MIL illuminates, freeze frame data stores, and Mode 6 test results store (FIGURE 8-15).

FIGURE 8-15 The oxygen or air-fuel ratio heater monitor illuminates the MIL when the PCM detects a fault on two consecutive trips. © AleksejLysenko/Shutterstock

AF sensor heater testing is similar to oxygen sensor heater testing. The only difference is that most AF sensor heater voltage is duty cycled. You can monitor the duty cycle voltage using a DMM or DSO. Monitoring the duty cycle from engine cold start to warm verifies whether the PCM is supplying voltage (or ground if ground controlled) correctly to the AF sensor heater. Use the Mode 6 test result data to assist in your diagnosis if an AF heater DTC is stored. For example, do the data indicate an open circuit (current value is too low) or a short circuit (current level is too high)? This will help you plan your circuit and component testing as you use the related DTC diagnostics in the service information. To test the AF sensor heater circuit, follow the steps in SKILL DRILL 8-3. SKILL DRILL 8-3 Testing an AF Sensor Heater Circuit

1. When determining whether the AF sensor heater is operating correctly, the technician can check for a fault within the circuit.

2. The first step is to conduct a visual inspection on the AF sensor and associated wiring.

4. While the connector is unplugged, use an ohmmeter to access the heater wires on the sensor. Using the ohmmeter, probe the heater terminals in the connector. The reading on the ohmmeter will validate whether the element has failed. Measure resistance of the sensor heater and verify whether it is within normal limits. Most sensor heater elements fail open and will show a value of OL on the DMM. A shorted element is indicated by a very low ohms reading (close to 0 Ω).

5. Next you need to verify the power and ground on the body side of the AF sensor. While the connector is unplugged, use a voltmeter to probe the power and ground terminals on the engine wiring loom.

6. Validating the inputs to the AF sensor allows the technician to determine which part of the circuit is at fault causing the

heater to not operate. If it is determined that the heater element has failed, then the AF sensor will need to be replaced.

7. Once the AF sensor is replaced, the technician should reverify the heater element operation with the scan tool. © Jones & Bartlett Learning

Repairs include replacing a failed sensor (the heater is part of the sensor and not serviceable), harness repairs, and in rare cases a failed PCM. The final step of the strategy-based diagnostic process is to verify your repair. It is critical that you perform the applicable drive cycle for the oxygen sensor heater circuit and verify that the Mode 6 data indicate the heater is functioning normally. Also, since this DTC most likely prevents other monitor tests from running, it is prudent to verify that fuel trim is within normal limits and that the related oxygen sensor monitor has run and passed. Failure to do this can lead to a comeback based on the MIL turning ON. To the customer, the MIL ON is a repeat of the same fault, even though it may now be due to a different component. You can avoid this by completing all relevant monitors. If you find a new fault, you must then diagnose and repair that fault (once the customer approves the additional work) and then repeat this final process again.

Case Study: HO2 Sensors or Wide Band Sensors A 2012 Honda Civic with a 1.8-L engine is in for the check engine light ON. The technician used scan tool Mode 3 to retrieve DTC P2A00, A/F ratio sensor range/performance problem. The vehicle has 39,487 miles. This is the second visit by the customer for this DTC, as it was in a week earlier and the technician replaced the thermostat and then cleared DTCs. This is now a comeback situation. The technician viewed the Mode 6 AF ratio sensor test results and the output voltage of the AF sensor was too low at 1.93 V. The technician viewed PID data and noted the long-term fuel trim was varying between lambda values of 1.0 and 0.93. Short term was varying between 0.87 to 1.2 lambda. The technician

referred to Honda’s Advanced Diagnostics (FIGURE 8-16) and noted that this DTC sets when AF ratio sensor output voltage is 2.8 V or less, or 4.8 V or more.

FIGURE 8-16 DTC P2A00 diagnostics show the malfunction threshold and possible causes of the fault. Note that the Mode 6 test results show that the AF ratio sensor voltage exceeded the low-voltage threshold point of 2.8 V (1.93 V was measured during the monitor test). © Jones & Bartlett Learning.

The technician viewed the AF sensor output voltage on the scan tool and it was varying between 1.8 and 2.2 V. This voltage is too low. The technician verified MAF operation and smoke checked the intake

and exhaust systems for leaks. None were found. The technician followed the DTC troubleshooting procedure and replaced the AF ratio sensor. The technician cleared DTCs and then test-drove the vehicle to run the AF sensor monitor. A review of the Mode 6 data showed the AF sensor data was still below 2.8 V. The service information did not provide any other pathways, so the technician called the manufacturer’s technician assistance line. The technician assistance line reviewed the scan data with the technician and performed Mode 8 onboard tests to vary the injector on-time. The AF ratio data were still staying below 2.8 V during the test. The technician assistance agent had the technician check voltage drop on the AF sensor signal wires and they were both okay (less than 50 mV, with one being 12 mV and the other 4 mV). The technician assistance agent then had the technician replace the PCM. The AF sensor voltage was now varying between 3.1 and 3.9 V. The technician cleared DTCs and performed a PCM relearn procedure, then test-drove to run the AF sensor monitor. Checking Mode 6 data showed the AF sensor passed and the test results showed a voltage of 3.31 V. The vehicle is now repaired. The PCM is not often the cause of the fault, yet it does happen. The strategic diagnostic process, integrating the related service information and the technician and, in this case, a master technician assisting by phone, eliminated all possible causes before replacing the PCM. The result is a repaired vehicle. Regarding the thermostat replacement, the technician did not follow the related DTC diagnostics for the DTC stored. This demonstrates the importance of applying your knowledge and integrating the service information into your diagnostics. The thermostat was not related to this fault and should not have been replaced.

Secondary Air Systems 8-6 Diagnose secondary air system concerns.

Secondary air systems have been used on some vehicles since 1966. These early systems pumped air into the exhaust to oxidize unburned fuel and carbon monoxide to reduce emissions. These early “smog pump” systems increased in use until the catalytic converter came into use in the mid-1970s, then their use began to decline. Most of these early systems used a belt-driven pump and a vacuum controlled valve to control the air flow. The low-pressure smog pump air was controlled to flow into the exhaust manifold(s) at cold start, into the catalyst to help oxidize HC and CO, or in a bypass mode during deceleration. Some 4-cylinder engines were able to use a system that drew in air using the negative pressure created from the widely spaced exhaust pulses. These were often called pulse-air systems. Most of these systems were pre-OBD II and are not covered in this chapter, but more detail will be provided on them in the Engine Emissions Testing and Failure Diagnosis chapter. The current secondary air systems are used on vehicles that generally have high emissions at vehicle startup (FIGURE 8-17). Adding air to the exhaust helps heat up the air-fuel ratio sensors, oxygen sensors, and the catalysts very quickly.

FIGURE 8-17 Most vehicles that require a secondary air system use an electric motor to operate the pump. © Jones & Bartlett Learning.

The air-fuel mixture is rich at cold engine start. This is because a cold engine inhibits the liquid fuel

from turning into a vapor so it can burn in the cylinder. Remember that liquid gasoline does not burn. It must be a vapor so it can mix with the oxygen in the air to ignite and burn. The PCM creates the rich mixture by increasing the fuel injector on-time. The ECT sensor is a critical input for the PCM to control the fuel mixture accurately at cold engine start. One result of the rich air-fuel mixture is that unburned hydrocarbons exit the cylinders into the exhaust. The catalyst is also cold and very much below operating temperature, as are the oxygen or air-fuel ratio sensor(s). The use of secondary air during cold engine starts allows for faster warmup of the oxygen or AF sensor(s) and the catalyst(s). Pumping air into the exhaust allows it to combine with the unburned fuel and continue to burn due to the heat of the exhaust gas. This burning of the small amount of fuel provides heat to bring the oxygen or AF sensor(s) and catalyst(s) up to operating temperature as quickly as possible. This allows the PCM to enter closed loop quickly, which reduces exhaust emissions and increases fuel mileage. OBD II secondary air systems often use the following components: An electric motor to pump the air Hoses to connect the pump to the related exhaust connections One-way valves that allow the air to enter the exhaust but block exhaust from entering the system A solenoid or vacuum switching valve to control the amount of air entering the exhaust stream Some systems use a pressure sensor to monitor pressure in the air pump hoses

Secondary Air System Monitor The system may be monitored by operating the air pump during deceleration and noting a change in airAF or oxygen sensor readings. This indicates the pump and related components can pump air into the exhaust stream. An oxygen or AF ratio sensor signal that goes lean when the secondary air system is operated during the monitor indicates that air flow is present and the test passes. No change in sensor signal indicates a possible blockage or pump issue. Engines with two-cylinder banks monitor operation on Bank 1 and Bank 2. A monitor test failure on both banks is usually isolated to the pump or related electronics to operate the pump. A monitor test pass for one bank and fail for the other bank usually indicates the pump is okay. Isolate the cause to a component isolated to that cylinder bank, such as a one-way check valve or damaged air hose. Another monitor strategy uses a pressure sensor in the system (FIGURE 8-18). The pressure sensor detects an increase in pressure when the air pump is operating during the monitor test. Pressure that is too high may indicate a blockage in the air stream or an air-switching valve that is not opening. Pressure that is too low may indicate a leak in the air supply hose portion of the system.

FIGURE 8-18 Some secondary air systems use a pressure sensor to monitor system pressure during operation. © Jones & Bartlett Learning.

Description Diagnosing this system requires following the related DTC diagnostic flow chart. Often, you can use the active test function of the scan tool as part of the diagnostics to verify pump and control valve operation. The one-way check valves are subject to high heat from the exhaust. Failure of these valves can damage the hoses and other components as high temperature exhaust gas is allowed past them and moves upstream of the exhaust toward the fan housing.

Test the Secondary Air System Motor The secondary air motor is tested as follows (FIGURE 8-19):

FIGURE 8-19 Secondary air motor diagnosis is not much different than checking any other type of motor circuit. © Jones & Bartlett Learning.

Use the scan tool output/active test to verify PCM control of the motor. Perform circuit tests to verify voltage and ground are present when the circuit is commanded ON with the scan tool. Isolate circuit faults including an open, high resistance or short to ground and repair as necessary. Replace the motor or repair the related wiring as required. Drive the vehicle according to the secondary air drive cycle to ensure the monitor completes and passes.

Test the Secondary Air System Check Valves The secondary air system uses control valves to control air flow in the system. Check valves are used to prevent exhaust gas from entering the secondary air system. Control valves are used to manage when air should be sent into the exhaust; if duty cycled, they can modulate the flow of air into the exhaust. Some systems use control valves that integrate the check valve (one-way valve) into one component. Boxer and V-type engines will most likely use one check/control valve per cylinder bank (FIGURE 8-20).

FIGURE 8-20 The secondary air system may use check valves, a control valve, or both. © Jones & Bartlett Learning.

Description Check valves may make a popping noise when they fail, as they are allowing exhaust gases into the secondary air system. The heat from the exhaust can damage the air system hoses and other components. Visually inspect the valve and replace if damaged. You can verify operation by using the scan tool to turn the air pump ON, and with the valve removed from its mounting location you can determine whether air flows correctly through it. You can use an air nozzle under light air pressure to determine whether the valve blocks air from going back toward the air pump. Replace any failed check valves. Control valves can usually be commanded ON or OFF using the scan tool. With the air pump ON, verify that no air flows through the valve when it is OFF and closed and that air does flow through when it is commanded ON. Valves that fail the test may be at fault or it could be in the related circuit wiring, relay, or fuse. Check that all system voltages are normal before replacing an electronically controlled valve. Drive the vehicle according to the secondary air drive cycle to ensure the monitor completes and passes before returning the vehicle to the customer. The secondary air system can leak at the following areas: The fan housing System hoses and fittings Check valves Control valves Exhaust manifold to cylinder head surfaces Use of a smoke-generating machine connected to the system can quickly isolate areas where a leak

is present (FIGURE 8-21). A leak can reduce system volume and pressure and could cause the system monitor to fail. If all components appear to function correctly, a leak check of the system is a prudent test to verify all is okay. If any leak is found, repair or replace the related component(s) to eliminate the leak. Recheck the system with the smoke test after repairs to verify that the leak(s) is now repaired. Drive the vehicle according to the secondary air drive cycle to ensure the monitor completes and passes before returning the vehicle to the customer. To inspect and test the secondary air system for air leaks, follow the steps in SKILL DRILL 8-4.

FIGURE 8-21 Use of a smoke test machine can isolate leaks and faulty control or check valves. © Jones & Bartlett Learning.

TECHNICIAN TIP It is okay to test the secondary air system using ambient air. Testing the EVAP system requires the use of nitrogen for testing, as pumping air (oxygen) into the fuel tank and EVAP-related components can lead to a fire or explosion due to a spark from the in-tank fuel pump.

SKILL DRILL 8-4 Inspecting and Testing the Secondary Air System for Air Leaks

1. Obtain your assigned vehicle, smoke machine, and related tools.

Access the secondary air service information. You need a system diagram to review system operation for your assigned 2. vehicle. The service information may or may not provide a procedure for a leak test using a smoke machine. If it does, then follow the procedure. If it does not, continue with the following steps.

3. Locate a spot to connect the smoke machine. The ideal location is to disconnect the hose that connects to the secondary air pump (fan housing). Connect the smoke machine to the hose.

Operate the smoke machine to check for leaks between the air pump and any related control or check valves. If there are 4. any leaks, note them for your RO and show your instructor.

5. Use the scan tool Mode 8 to operate the secondary air control valve(s). This will open the valve or valves (V-type and boxer-type engines may have a control valve for each cylinder bank) and allow the smoke to enter the exhaust manifold(s). Note whether there are any leaks. Use the scan tool to close the valves by turning OFF the output command test of them. Leave the fan to control valve hose disconnected for step 6.

6. It is also possible to check the exhaust for air leaks by connecting the smoke machine to the exhaust at the tailpipe. Use the tailpipe adapter to connect the smoke machine to the exhaust system. Turn the smoke machine ON and check for leaks in the system. Secondary air leaks will be tested up to the control valves or check valves. Smoke coming out of the fan housing hose indicates that the check valve or control valve has failed. On V-type or boxer-type engines, you may be able to use hose pinch pliers to isolate which side/bank of the system has the fault if they are connected with a rubber-type hose. If the connection to the check valve or control valve is a nonflexible hose/metal line, you will have to perform a visual inspection to isolate if one or both valves have failed.

7. Reconnect the hose to the fan/pump housing and any other hoses or components. Torque fasteners as required. Review the smoke test results with your instructor.

8. Use the scan tool to clear any DTCs that may have stored during your testing of the secondary air system. 9. Return all tools to their storage location. © Jones & Bartlett Learning

WRAP-UP Ready for Review The oxygen sensor reads the oxygen content within the exhaust system so the PCM can adjust the fuel ratio within the engine. Heating the oxygen sensor helps get it operating quicker so the PCM can get into closed loop as quickly as possible. Using a DSO helps to visualize the operation of the oxygen sensor so the technician can identify a failure throughout the range of the oxygen sensor. Wide-band oxygen sensors create an exact reading of the oxygen content within the exhaust system so the PCM can adjust the fuel ratio more precisely. The secondary air system introduces fresh air into the exhaust system to help with catalyst conversion. Increasing the air to the catalyst promotes the conversion of emissions to less volatile substances. Using the check valves, the PCM can control when air is introduced into the exhaust system so the engine will not be under a load in situations that are not ideal to emission conversion. When testing the operation of this system, the technician should test the air pump and all valves related to it.

Key Terms AF sensor Abbreviation for the air-fuel ratio sensor. This sensor determines the air-to-fuel ratio based on oxygen levels in the engine exhaust gas. Available Scan tool data that indicate the identified noncontinuous monitor is installed on the vehicle. Bank 1 and Bank 2 An identifier for the location of the fuel trim data (and related AF or HO2S sensor) on the engine. Some manufacturers use cylinder 1 as the location for Bank 1 whereas others may choose the side of a V-type or boxer-type engine layout. Inline engines have only one cylinder bank. Complete Scan tool data that indicate the related monitor has successfully run. It does not mean it has passed, only that the test or tests are complete. Fail Scan tool data that indicate a noncontinuous monitor has run, completed, and failed. HO2S Abbreviation for heated oxygen sensor. This sensor detects exhaust gas oxygen in the form of a varying voltage signal. Incomplete Scan tool data that indicate a monitor test has not run. This may be due to an incomplete drive cycle or enable conditions were not met. Malfunction threshold The limit(s) that monitor data must exceed to set a pending or current DTC. This is found in the related DTC information. Monitor strategy A brief list of information on how and when the monitor runs during engine operation found in the DTC information. Oxygen or A/F sensor heater monitor The OBD II monitor that detects a fault for the heater or heater circuit. Oxygen or A/F sensor monitor The OBD II monitor that verifies oxygen or air-fuel ratio sensor operation is within test limits. Secondary air system monitor The monitor verifies the secondary air system delivers fresh air to the exhaust. Two-trip DTC A DTC that requires two consecutive trips for the malfunction threshold to exceed limits to store a DTC and illuminate the MIL. A pending DTC stores on the first trip.

Review Questions 1. Review the air-fuel monitor test shown on the next page. How long does the air-fuel response time test take? a. 10 seconds b. 60 seconds c. 360 seconds d. 15 minutes or less

© Jones & Bartlett Learning.

Description 2. Enabling conditions for DTC P2A00, AF sensor slow response are shown below. All of the following will inhibit this monitor from running EXCEPT: a. a fuel system DTC. b. the engine is running at 4150 rpm.

c. the vehicle traveling at 45 mph. d. ECT at 80o F.

© Jones & Bartlett Learning.

3. Which of the following may cause an oxygen sensor or air-fuel ratio DTC to store? a. Contaminated MAF sensor b. Exhaust manifold to cylinder head air leak c. Low oil pressure to the VVT control valves d. Turbocharger boost control valve stuck closed 4. The catalyst monitor relies on which sensors to determine catalyst monitor data? a. Air-fuel ratio sensors and/or oxygen sensors b. CKP and oxygen sensors c. ECT and air-fuel ratio sensors d. MAF and air-fuel ratio sensors 5. Which component prevents exhaust gas from entering the secondary air hoses and pump assembly? a. One-way air check valve b. Exhaust back pressure relief valve

c. VVT internal EGR effect d. Secondary air electric pump relay 6. Oxygen sensor testing includes all of the following EXCEPT: a. creating a small vacuum leak to create a lean condition. b. snapping throttle and monitoring reaction time. c. verifying open loop operation. d. verifying sensor approaches 0.1 V for lean and 0.9 V for rich conditions. 7. The secondary air system helps reduce all of the following EXCEPT: a. carbon monoxide. b. hydrocarbons. c. oxide of nitrogen (NOx). d. catalyst warmup time. 8. Refer to the secondary air system diagram shown for a V8 engine. Which of the following is correct? a. The air injection control driver receives B+ from the ECM. b. The air pump motor is ground controlled. c. Connector D74 pin 98 provides B+ to the emissions control valve set. d. The integration relay is source controlled.

© Jones & Bartlett Learning.

Description 9. A failed secondary air check valve may be indicated by all of the following EXCEPT: a. an abnormal increase in long-term fuel trim. b. B1S1 and B2S2 AF or HO2S values are leaner than normal. c. B1S1 and B2S2 AF or HO2S values do not change when the air pump is ON. d. Secondary air can only flow through the valve and into the exhaust stream. 10. The HO2S heater monitor test result data show 88000. This equates to which of the following results? a. Shorted heater circuit b. Open heater circuit c. Approximately 88 Ω

d. Approximately 0.0088 Ω

© Jones & Bartlett Learning.

ASE Technician A/Technician B Style Questions 1. Technician A says the EVAP monitor checks for purge flow volume. Technician B says the EVAP monitor checks for system leaks only. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B 2. Refer to the scan tool screen shot shown on the next page. Technician A says the data for the HO2S switch point voltage have no limit value for this vehicle. Technician B says all the HO2S test results are within normal range. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B

© Jones & Bartlett Learning.

Description 3. Refer to the scan tool information shown below. Technician A says all system tests have passed except the EVAP system, which has failed. Technician B says this vehicle does not have a secondary air system. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B

© Jones & Bartlett Learning.

4. Refer to the EVAP monitor test information shown on the next page. Technician A says the MIL illuminates as soon as a fault is detected. Technician B says the EVAP system is tested one time for each driving cycle. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B

© Jones & Bartlett Learning.

5. Refer to the EVAP monitor information shown for question 4. Technician A says this monitor test will not run if the ambient air temperature is above 85° F. Technician B says this monitor test runs after the vehicle has been driven for 5 minutes or more. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B

© Jones & Bartlett Learning.

6. Refer to the catalyst monitor test information shown below. Technician A says this monitor test will not run if a DTC is stored for an EVAP system leak. Technician B says this monitor test will run with the transmission in second or third gear. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B

d. Neither Technician A nor Technician B

© Jones & Bartlett Learning.

7. Refer to the heated air-fuel ratio sensor heater monitor information shown below. Technician A says the monitor will not run if a DTC is stored for the IAT sensor. Technician B says the monitor can set a DTC within 3 seconds after the heater is turned ON. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B

© Jones & Bartlett Learning.

8. Technician A says the noncontinuous monitors will all run on every drive cycle. Technician B says AF ratio monitor tests run when the engine is ON. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B 9. Refer to the secondary air system monitor enabling conditions shown below. Technician A says this monitor will not run if other system DTCs are stored. Technician B says the engine must be running for this DTC to store. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B

10. Technician A says Mode 6 monitor test results may be displayed in hexadecimal format. Technician B says a Mode 6 test monitor that is incomplete indicates the system has failed the monitor test. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B

© Jones & Bartlett Learning.

CHAPTER 9

Noncontinuous Monitors: Exhaust Gas Recirculation and Catalyst Diagnosis LEARNING OBJECTIVES After studying this chapter, you should be able to: 9-1

Describe the operation of the exhaust gas recirculation system.

9-2

Diagnose exhaust gas recirculation system concerns.

9-3

Describe the operation of the OBD II catalyst system monitor.

9-4

Diagnose catalyst system concerns.

YOU ARE THE AUTOMOTIVE TECHNICIAN A check engine light concern leads you, the technician, to DTC P0420 Catalyst Efficiency Below Threshold. Which of the following will most likely be required for your diagnosis? View KOER data list parameters. Review DTC-related service information. View OBD II Mode 5 data. View OBD II Mode 6 data. Review freeze frame data. Inspect the EVAP system for leaks. Perform a MAP and/or MAF inspection and related testing. Check for an exhaust leak. Inspect HO2S or AF ratio sensors. Verify proper fuel pressure.

The catalyst monitor stores test result data. You will use these data along with the service information to develop a diagnostic strategy. Advanced engine performance diagnosis requires you to understand more than the component operation and related component testing knowledge. The master diagnostic technician can do the following: Review and analyse Mode 6 monitor test results. View PID data and determine the status of inputs and outputs that may affect catalyst operation. Perform applicable output tests to verify whether components that can affect catalyst operation are operating within or out of normal range. Use non-scan tool–based tests, including measuring circuit voltages and viewing input or output oscilloscope waveforms. Refer to service information to develop a strategy-based diagnostic plan that verifies related systems are working correctly and isolating those that are not.

Introduction The catalyst monitor to the novice may be seen as an alert that the catalyst has failed, but it is not. The monitor looks at catalyst efficiency, rather than whether it is okay. Any item that can affect catalyst efficiency must be checked to determine whether it is also okay. The following sections prepare you with exhaust gas recirculation (EGR) and catalyst operation and related test procedures so you can apply the strategy-based diagnostic process and repair the vehicle rather than toss parts at an illuminated malfunction indicator lamp (MIL) diagnostic trouble code (DTC).

EGR Operation 9-1 Describe the operation of the exhaust gas recirculation system.

Exhaust gas recirculation (EGR) functions to reduce oxides of nitrogen exhaust gases that form during the combustion process. Air is made of approximately 79% nitrogen, 20% oxygen, and 1% other gasses. Nitrogen is not part of the combustion process. The combustion process uses fuel expressed as HC (hydrocarbons) and oxygen, and upon ignition creates heat to push the piston down or rotate the rotor in a Wankel engine. The byproducts of perfect combustion would be water vapor and carbon dioxide. Nitrogen would simply pass through the engine and exit as nitrogen. Very high combustion pressures and temperatures cause some nitrogen atoms to combine with oxygen to form NO2, but there may be other combinations; this byproduct is referred to as NOx when describing the burning of fossil fuels. NOx is a major contributor to the reddish-brown haze over major metropolitan areas, but no matter where it occurs it also contributes to the creation of acid rain (FIGURE 9-1). For this reason, the Environmental Protection Agency (EPA) began requiring a reduction in NOx from automotive internal combustions engines and other sources that burn large amounts of fossil fuels, including steel mills and electrical power generating plants, beginning in the early 1970s.

FIGURE 9-1 EGR functions to limit the formation of NOx in the exhaust, which contributes to the brown haze seen in unhealthful air. © Jones & Bartlett Learning.

The difficulty in controlling NOx is that at the same time the fuel and ignition system engineers were trying to reduce HC and CO by keeping the air-fuel ratio near 14.7:1 (stoichiometric ratio), NOx levels are already increasing (FIGURE 9-2). The reason is that as the air-fuel ratio becomes leaner and HC and CO emissions reduce, the combustion temperature increases, as there is less fuel to absorb heat as it enters the combustion chamber during the intake stroke. The leaner mixture also burns faster and at a higher temperature. NOx increases the leaner the mixture goes, until it becomes too lean to support combustion and a lean misfire occurs. This section focuses on systems in use as part of OBD II systems on vehicles from model year (MY) 1996 and later.

FIGURE 9-2 NOx values increase while HC and CO levels decrease as they approach the stoichiometric air-fuel ratio. © Jones & Bartlett Learning.

Description NOx on non-VVT (variable valve timing) engines has primarily been controlled by using an EGR valve and the catalytic converter (FIGURE 9-3). The EGR valve connects the vehicle exhaust gas stream to the intake manifold system. The EGR valve operates to allow a metered amount of exhaust gas to enter the intake system. Exhaust gas is inert, which means it does not contain oxygen, Without oxygen, the

exhaust gas mixes with the incoming air-fuel mixture. The inert exhaust gas takes up some of the volume in the combustion chamber. This reduces the space available for the air-fuel mixture. The PCM controls EGR valve position and at the same time reduces injector on-time. This reduces the fuel amount entering the cylinder during EGR operation because there is less room for the oxygen-rich air charge. It is important to note that both air and fuel are being controlled so that the air-fuel ratio does not become leaner, only that there is a smaller amount of air and fuel in the combustion chamber.

FIGURE 9-3 The EGR valve is often found on non-VVT engines to reduce NOx emissions. VVT engines may also use an EGR valve to provide more NOx reduction than VVT provides alone. © Jones & Bartlett Learning.

At first, it may seem that introducing hot exhaust gas into the engine cylinders during the intake stroke would increase cylinder temperature. That is not the case. Yes, exhaust gas is very hot; however, the compression stroke increases the pressure and temperature of the incoming fresh air charge regardless. The inert (little or no oxygen) exhaust gas takes up space in the cylinder, which reduces the total air-fuel amount (not the ratio) inside the cylinder. This creates a smaller amount of the air-fuel mixture, which reduces the overall temperature inside the cylinder and reduces NOx emission levels. This reduced amount of air and fuel burns cooler, and NOx creation is reduced. Engine power and combustion stability are also reduced when using EGR. EGR is not used under the following conditions: Engine idle, because it would cause misfires or possible engine stall Acceleration, because EGR reduces engine power output Wide open throttle for passing or merging, because EGR reduces power Cold engine operation, because it would promote misfires or engine stalling

EGR is used during steady cruise and some very light throttle increases. This is where NOx creation is the highest. The EGR system works to reduce combustion temperatures, and any NOx that is created is then dealt with in the catalytic converter(s). The EGR valve has been vacuum controlled for many years on many vehicle applications. An applied intake manifold vacuum is used to open the valve diaphragm and allow exhaust gases to flow into the intake manifold (FIGURE 9-4). Pre-computer-controlled EGR valves often relied on exhaust back pressure or the use of vacuum amplifiers and reducers to modulate the intake manifold vacuum signal. These early EGR systems were very crude and caused a great deal of engine performance–related customer concerns, including stalling, surging at a steady cruise, and increased misfires, which increase engine vibrations and reduce power output. You are unlikely to work on these early systems unless you are dealing with a vehicle from around 1973 through the early 1980s. Computerized engine controls allowed the powertrain control module (PCM) to modulate EGR valve position and thus reduce many of the early EGR customer concerns.

FIGURE 9-4 The EGR valve may be vacuum controlled in some applications. © Jones & Bartlett Learning.

OBD II vacuum-controlled EGR systems use PCM control and various back pressure monitoring to control how much the valve opens. For example, Ford uses a Delta Pressure Feedback EGR (DPFE) sensor that monitors exhaust pressures between two points inside the EGR tube that is divided by a fixed restriction (FIGURE 9-5). The data are used by the PCM to control the electric vacuum regulator using a duty cycle voltage to precisely regulate the vacuum at the EGR valve and control EGR flow into the intake manifold.

FIGURE 9-5 Some EGR systems monitor exhaust back pressure to help the PCM precisely meter EGR gases into the intake manifold. © Jones & Bartlett Learning.

Description TECHNICIAN TIP The Ford DPFE EGR system uses a vacuum controlled EGR valve, an electric vacuum regulator, a DPFE sensor, and an EGR tube with a fixed orifice inside it. The PCM modulates the vacuum applied to the EGR valve by applying a duty cycle voltage signal to the electronic vacuum regulator valve (basically a vacuum control solenoid valve). The duty cycle voltage applies a percentage of source voltage to the vacuum regulator valve, which controls the amount of manifold vacuum that is applied to the EGR valve. The DPFE sensor is similar to a MAP sensor, but it monitors two vacuum signals: one before the fixed orifice restriction in the EGR tube and one after. As the EGR valve opens, exhaust gas flows through the EGR tube across the fixed orifice restriction. The opening of the EGR pintle connects intake manifold negative pressure (vacuum) to the EGR tube on one side of the restriction and exhaust pressure is on the other. The DPFE converts these pressures to a voltage signal just like a MAP sensor. The PCM uses these voltage values along with the programming data map to control the electric vacuum regulator duty cycle percentage. This modulates EGR valve position to allow for the correct amount of EGR to reduce NOx while maintaining required engine performance.

Other systems may use an EGR modulator or transducer to help modulate the control of manifold vacuum to the EGR valve. Notice that the EGR modulator valve shown in FIGURE 9-6 is connected to

exhaust pressure on one side and to intake manifold vacuum on the other. The modulator works in conjunction with the EGR vacuum switching valve (vacuum solenoid), which is often duty cycled to also help modulate EGR operation.

FIGURE 9-6 Some EGR systems use an EGR modulator or transducer to help control EGR flow into the intake manifold. © Jones & Bartlett Learning.

Description Many manufacturers use electronic EGR valves. The PCM directly controls the valve by duty cycling the voltage to the valve solenoid(s) (FIGURE 9-7). The duty cycle control allows the PCM to open the valve from a small amount to wide open based on conditions.

FIGURE 9-7 Some EGR systems use an EGR valve that is directly controlled by the PCM. These valves are electronically (versus vacuum) operated. © Jones & Bartlett Learning.

Some designs connect the exhaust gases via a pipe from the exhaust manifold to the intake manifold. Others have them mounted on the cylinder head, and the valve controls access to cylinder head passages that route the exhaust gases into the intake system. No matter the EGR system design, it will most likely clog at some point during the vehicle life cycle. This is because exhaust gas contains water and carbon-based particulates. The water mixes with these particulates and they stick inside the passages, building up over time. This buildup reduces EGR flow and can eventually completely block any EGR gases from reaching the intake manifold (FIGURE 9-8). Function can be restored by cleaning the passages, although it is time consuming depending on system design and access to components.

FIGURE 9-8 Some EGR systems use a pipe to connect the EGR valve to the exhaust while other systems have EGR passages cast into the cylinder head. © Jones & Bartlett Learning.

EGR System Monitor Operation 9-2 Diagnose exhaust gas recirculation system concerns.

OBD II monitors the EGR system as part of the Mode 6 noncontinuous monitors. The monitor functions to ensure that the EGR system can flow the required amount of exhaust gas and that the related components are also functioning correctly. Pre-OBD II systems monitored items including exhaust gas temperature and EGR valve position in an attempt to verify operation; however, these were unable to detect flow issues due to carbon buildup or a problem with the EGR valve opening too little or too much. Most EGR system monitors use a manifold absolute pressure (MAP) sensor to verify sufficient EGR flow (FIGURE 9-9).

FIGURE 9-9 EGR monitor test results are listed as part of overall Mode 6 test data. © AutoEnginuity.

Description Failure of the EGR flow test may indicate a faulty EGR valve, EGR vacuum or electronic controls, EGR pressure transducer, MAP or other sensor fault (e.g., DPFE), or plugged EGR passages. Remember that EGR affects idle stability and power output so the valve cannot be opened as part of the monitor test under these conditions. The engineers designed the monitor to open the valve during a throttle closed deceleration event, such as approaching a red light or to slow for traffic. Opening the EGR valve under this condition is not noticeable to the driver, but the MAP sensor notices a change in intake manifold pressure when the valve is opened. A closed throttle during deceleration creates a very high negative pressure, or vacuum, in the intake system. Opening the EGR valve adds exhaust gas into the intake and raises the pressure. When the MAP sensor detects that the pressure rise indicates there is normal EGR flow, the monitor completes and passes the test. If the EGR valve is opened but there is little or no pressure change, then the monitor completes but the test fails. Most EGR monitors require two consecutive drive cycles to complete and have fail test results before a DTC stores and the MIL is illuminated. Some vehicle manufacturers run the monitor only when a deceleration event allows the PCM to enter fuel cut mode. This mode turns off the fuel injectors during deceleration to increase fuel economy and reduce emissions. Ford vehicles may use a MAP sensor and a DPFE sensor as part of the EGR monitor as seen in FIGURE 9-10. This sensor compares the manifold pressure vacuum to the exhaust pressure that is measured by the DPFE sensor (FIGURE 9-11). The exhaust and MAP signals change as the EGR valve is opened. This one sensor monitors both signals, noting the change between MAP and exhaust pressures as the EGR valve is opened. The data are found under EGR Mode 6 test results. This sensor can be affected by moisture, especially the earlier sensors that used an aluminum housing. Basic DPFE tests include the following:

FIGURE 9-10 EGR monitor diagnostics list the related code(s), description, possible causes, and related tests as part of the diagnostics.

© Jones & Bartlett Learning.

Description

FIGURE 9-11 The Delta Feedback sensor measures the flow of the EGR valve to verify it is operating correctly. © Jones & Bartlett Learning.

5 volt reference present Sensor ground voltage is less than 50mV Signal voltage is 4.5 to 1.1 volts with key on engine off A voltage outside of this range usually indicates a DPFE sensor fault If OK, start the engine and let idle. The voltage should be the same. If not, it is mostly likely due to an EGR valve stuck open or the EGR valve is receiving a vacuum signal, which may be caused by the electronic vacuum regulator or the PCM. Carbon may have plugged the restriction orifice, may need to verify by remoiving it and inspecting. The applicable service information will detail the operation for the EGR monitor of the vehicle you are working on. The most common generic code is P0401 for insufficient EGR flow detected during the EGR monitor test. Other DTCs can store that are specific to a particular component, such as a MAP sensor or EGR position sensor; however, these will most likely set as part of the continuous component monitor and will prevent the EGR monitor from running, as these components are required to be operating normally. Let’s first take a look at inspecting the system components that have not been covered to this point.

EGR Valve Inspection

Vacuum EGR Valves General EGR valve testing is determined by the type of valve: vacuum or electronic. Vacuum-controlled EGR valves open when intake manifold vacuum is modulated through a vacuum switching valve. The PCM controls the strength of the vacuum signal through duty cycle control of the vacuum switching valve. For example, a duty cycle of 75% will modulate the voltage to the vacuum switching valve to about 9 V. This controls how far the vacuum switching valve pintle opens, which controls how much vacuum is applied to the EGR valve. The EGR valve has a flexible diaphragm that forms a sealed chamber. The vacuum hose from the vacuum switching valve connects to the chamber. The negative pressure created from the intake manifold vacuum signal lifts the EGR valve pintle to open the passageway that connects exhaust gas to the intake manifold. To check a vacuum-controlled EGR valve, follow the steps in SKILL DRILL 9-1. SKILL DRILL 9-1 Checking a Vacuum EGR Valve for Operation

1. Obtain your assigned vehicle and related tools, including a hand-operated vacuum pump. 2. Obtain the EGR-related service information for the vehicle, including EGR flow-related DTC diagnostics and the system electrical and vacuum diagrams. 3. Inspect related vacuum lines for proper routing and connections, and no visible cracks or leaks.

4. Locate the vacuum hose that connects to the EGR valve. With the engine OFF, use a hand-operated vacuum pump to determine whether the valve holds vacuum and whether the valve pintle moves when vacuum is applied (you may have to remove the valve from the engine for this part of the test). Replace the valve if it does not hold vacuum or does not open when vacuum is applied. 5. You may be able to test the valve with the engine running. The general procedure is the same as in step 4; however, when you open the valve, the engine will idle very rough or may stall. This indicates the valve opened and the passages are clear from carbon buildup. If there is no change in engine operation when you apply vacuum, the valve is not opening or the valve opened but the EGR passages are clogged with carbon so little or no EGR gases enter the intake manifold. 6. Inspect and test the EGR vacuum switching valve. Review the related wiring diagram. Valves that are ground controlled by the PCM will have source voltage at both valve connector pins when the valve is OFF. Measure this voltage with the key ON engine OFF (KOEO). Note the voltage and compare it to specifications in the service information. 7. If applicable, use the scan tool Mode 8 output test to operate the vacuum switching valve. Monitor the control side of the circuit (usually the ground side). You will note a voltage based on the duty cycle percent. A 50% duty cycle would have between 6 and 7 V present on the control side of the circuit. A 100% duty cycle would have very close to 0 V present on the controls side of the circuit. You can also measure the duty cycle using that function of your digital multimeter (DMM). Note the readings from your test results. 8. EGR back pressure transducers/modulator may be able to be tested if applicable to your assigned vehicle. Refer to the related service information to test these components. The test usually has you isolate the transducer and then use a vacuum pump to verify it can hold a small vacuum. Perform these tests if these components are on your assigned vehicle and note your results. 9. Review your test results and create a repair order (RO) that summarizes your findings. Review with your instructor and let

them know whether the vacuum-operated EGR system on your vehicle is operating normally or requires a repair. © Jones & Bartlett Learning

TECHNICIAN TIP There are some EGR valves that must have back pressure applied for manifold vacuum to open them. Although these are not common on OBD II vehicles, you may encounter one. For these and the testing of any valve, be sure to follow the applicable service information test procedures.

Electronic EGR Valves Electronic EGR valves are usually tested with the scan tool output test (FIGURE 9-12). You can command the valve open with KOEO and then monitor the EGR position sensor parameter ID (PID) data to see how much the valve moves. Both vacuum and electronic valves and related EGR passages can be clogged by carbon buildup. This can sometimes be cleaned to restore normal operation. If you are unable to clean the valve it should be replaced. Note that some cleaners can damage the vacuum chamber diaphragms, the electronic solenoid coil windings, or the position sensor electronics. For this reason, it may be best to replace components rather than try to clean them, which could lead to a comeback situation. To test an electronic EGR valve, follow the steps in SKILL DRILL 9-2.

FIGURE 9-12 Using a scan tool, the technician can see whether the electronic EGR valve is being commanded ON or OFF and determine whether the valve is reacting appropriately. © Jones & Bartlett Learning.

TECHNICIAN TIP Ford DPFE sensor testing is similar to MAP sensor testing. It is critical that you use the correct service procedures for the vehicle you are working on, as some test readings may vary depending on the engine type. Also, this system does have technical service bulletins (TSBs) that may apply for common system-related issues, which can save you time because a resolution has already been found.

TECHNICIAN TIP EGR valve position sensors are not common on OBD II vehicles. Should you encounter this sensor, it is usually a three-wire sensor, with a 5-V reference, ground, and signal wires. The sensor usually has a range of 0.5 to 4.5 V, and the voltage increases as the EGR valve opens. Testing the position sensor is similar to testing a three-wire TPS. There should be less than 50 mV of voltage drop on any of the wires. Actuate the EGR valve and verify that the values change within service specifications. An open or short on the sensor wiring will usually store a DTC.

SKILL DRILL 9-2 Testing an Electronic EGR Valve with a Scan Tool

1. Obtain your assigned vehicle with an electronically controlled EGR valve and a scan tool capable of Mode 8, control of vehicle systems. 2. Obtain the related EGR inspection from the service information. 3. Connect the scan tool to the data link connector (DLC) and turn the vehicle ignition ON.

4. Use the scan tool menu to connect to the PCM and then select Mode 8, control on-board systems (the exact name of the function may vary between scan tool and vehicle manufacturers).

5. Operate the EGR valve (test may not be applicable on all vehicles or scan tools). This is usually done with the engine OFF while monitoring the EGR position data on the scan tool. Look for a change in EGR position when commanded open. 6. An opening valve indicates that the PCM can provide the output signal (usually a duty cycled path to ground). A valve that does not show any movement may be caused by the following: a. Open in circuit wiring b. Faulty valve c. PCM output drive has failed (If this is the case upon circuit and component testing then the PCM and the valve must be replaced.)

7. An opening valve based on a change in EGR position indicates the valve is okay; however, there may still be issues with proper EGR operation. A DTC for lack of EGR flow or a vehicle that has failed an emissions inspection test for high NOx indicates that the EGR passages may be restricted or plugged due to carbon buildup. This may be confirmed with a visual inspection of the EGR passages and/or using a smoke machine connected to the vehicle exhaust and noting smoke at the EGR valve connection port. 8. Complete your electronic EGR valve test by powering down the scan tool and turning the vehicle ignition OFF. Return the scan tool and any other tools used to their proper storage location. Create a repair order documenting the EGR valve test and the related test results. Review your findings with your instructor. © Jones & Bartlett Learning

System Leaks or Blockage EGR systems can develop leaks in the vacuum lines, EGR valve gaskets, and EGR-related plumbing (e.g., the pipe that connects the exhaust manifold to the EGR valve on some vehicles). A smoke machine is an excellent tool to check for leaks in some of these components. Connecting the smoke machine to the exhaust tailpipe can help you determine whether any exhaust-related EGR components, including the EGR base gasket, have a fault. Vacuum lines can be checked by connecting the smoke machine to the intake system. Look for smoke leaking from EGR-related vacuum lines, at the fittings, and where the line

connects to a component. EGR blockage inspection is usually indicated by an insufficient EGR flow DTC. If your inspection and testing show that all EGR components are operating normally you will have to inspect for the cause of a blockage. Usually you must remove the EGR valve to inspect for blockage at the valve (FIGURE 9-13). The blockage can be full or partial and can extend into the passages on both the exhaust and the intake side (FIGURE 9-14). That type of blockage requires extensive cleaning with throttle body cleaner and round wire brushes. Some wire brushes can be used with a handheld drill to snake through the passages. Some manufacturers have TSBs or related procedures in their service information for cleaning the EGR passages.

FIGURE 9-13 EGR carbon buildup can be cleaned using intake cleaner and wire brushes. © Jones & Bartlett Learning.

FIGURE 9-14 EGR diagnosis includes verifying the passages are clogged by carbon buildup. Effective EGR requires open passages from the exhaust to the intake. © Jones & Bartlett Learning.

Variable Valve Time and EGR The EGR monitor has almost vanished from use on gasoline engines in the last few years, with very few vehicles using an EGR system. Most engines now use variable valve timing, which can create an internal EGR effect by keeping the exhaust valve open during the intake stroke to draw in exhaust gas when required (FIGURE 9-15). The open exhaust valve during the intake stroke draws exhaust gas into the cylinder.

FIGURE 9-15 VVT engines sometimes still need EGR to help meet emission standards. If an EGR or VVT system failure occurs, the technician must fix that before evaluating the output of the engine. © Jones & Bartlett Learning.

EGR valves have been common on many hybrid powertrains because those engines often use an Atkinson cycle engine. This has the engine operating most often within a narrow operating range as lean as possible, so EGR is required on these engines. EGR valves are now reappearing on some nonhybrid vehicles even though they have VVT; however, they are also using the Atkinson cycle. An example is the 2018 Camry 2.5 L direct injected with port injection. This engine has electronically controlled VVT on both intake and exhaust camshafts; however, the engine uses an EGR valve with an EGR cooler (similar to what is found on diesel engines).

Atkinson Cycle Engines James Atkinson patented the Atkinson Cycle Engine in 1882. The focus of the variations in his engine designs from the traditional 4-cycle gasoline engine was the use of short intake stroke and a long power stroke. This was done with opposing piston designs at first, and then a complex connecting rod design that allowed for a short compression stroke but a long power stroke. The idea was to reduce fuel use and simplify engine design through the use of reed valves for intake and exhaust rather than a camshaftoperated valve train. Modern use of the Atkinson cycle is an adaption of the reduced intake stroke idea and applying it to the familiar 4-stroke piston gasoline engine. Variable valve timing is used on the intake camshaft. Retarding intake valve timing reduces the intake charge and also holds the intake valve open during part of the compression stroke. This pushes some of the air-fuel charge back into the intake manifold and reduces overall compression in the cylinder. The air-fuel mixture pushed back into the intake manifold is drawn into the next cylinder that is on the intake stroke. This reduces fuel use and

emission output. Atkinson cycle engines were primarily used in hybrid applications such as the Toyota Prius and Ford Fusion and Escape (FIGURE 9-16). The Atkinson cycle has found application in non-hybrid vehicles within the last few years. The lean mixtures used in Atkinson cycle engines create more NOx than a catalyst can handle, and the use of VVT is limited or nonexistent on the exhaust camshaft to provide an internal EGR effect since the intake valve is also open on each cylinder during part of the compression stroke. Most Atkinson cycle engines use an EGR valve to help reduce NOx levels.

FIGURE 9-16 The Toyota Prius and Ford Escape Hybrid use Atkinson cycle engines to improve fuel efficiency and provide a modulated output that synchronizes with the electric motor for total power output to the drive wheels. © Jones & Bartlett Learning.

OBD II Catalyst Systems Operation 9-3 Describe the operation of the OBD II catalyst system monitor.

Catalytic converter basics were introduced in the MAST Automotive Engine Performance text. The content presented here is focused on OBD II level vehicles from 1996 and later. The PCM monitors the primary catalyst for proper operation at the appropriate time during the drive cycle. Four-cylinder engines usually have one primary catalyst and a secondary catalyst just a little farther downstream in the exhaust system (FIGURE 9-17). The primary catalyst is usually located very close to the exhaust manifold—or may even be part of the manifold. The catalyst must reach operating temperature very quickly to reduce emissions, at temperatures of 400° to 600o F. Placement of the primary close to or part of the exhaust manifold makes this possible.

FIGURE 9-17 Inline engines often incorporate the main catalyst into the exhaust manifold for quick heat-up, and they use one or two additional catalysts just downstream from the main. © Jones & Bartlett Learning.

Boxer and V-type engines use a primary catalyst for each cylinder head and, like the AF sensors, are identified as Bank 1 or Bank 2 on the scan tool. Bank 1 is usually on the same side as Cylinder 1. These engines usually have a shared secondary catalyst or a secondary catalyst for each cylinder bank (FIGURE 9-18).

FIGURE 9-18 V-type and boxer engines usually have a Bank 1 and a Bank 2 primary catalyst. © Jones & Bartlett Learning.

Description

Catalyst Operation The catalyst is designed to oxidize carbon monoxide (CO) and unburned fuel (HC) into carbon dioxide (CO2) and water (H2O). It reduces NOx to oxygen and nitrogen. The catalyst uses three precious metals (platinum, palladium, and rhodium) to promote the reactions required. Most catalysts also include cerium for its ability to store and release oxygen to assist in the reduction of NOx and oxidation of CO and HC (FIGURE 9-19). The catalyst is constructed of a honeycomb substrate that is coating with the precious metals embedded into the coating. A catalyst promotes a reaction but is not used up by the reaction; therefore, the precious metals of the catalyst can last the life of the vehicle. Most catalysts are designed so that NOx is reduced first as this frees the oxygen from the nitrogen. The free oxygen is then used to oxidize the CO and HC. The use of cerium ensures that there is the correct amount of oxygen, by absorbing excess and releasing it when there is not enough.

FIGURE 9-19 The catalyst functions to promote reactions that convert pollution-type gases into non-pollution type gases. © Jones & Bartlett Learning.

Description The catalyst monitor determines whether the catalyst is operating as designed to reduce hydrocarbon, carbon monoxide, and oxide of nitrogen emissions (FIGURE 9-20). The test is done once per driving cycle for most vehicles when conditions are met; for this sample vehicle, it is a one-trip DTC. Other vehicles may use two-trip logic. The monitor test relies on monitoring the oxygen levels after the primary catalyst. Inline engines usually have only one primary catalyst, whereas V-type engines have a Bank 1 and a Bank 2 primary catalyst (FIGURE 9-21).

FIGURE 9-20 The catalyst is monitored as part of the OBD II Mode 6 noncontinuous monitors. © Snap-on Incorporated.

FIGURE 9-21 Some applications have more than one catalyst, which can allow for one to fail but the other to operate correctly. Always check both of the catalysts when diagnosing a fault. © Jones & Bartlett Learning.

The PCM monitors the oxygen storage capability of the catalyst(s) using the front AF ratio sensor and usually an oxygen sensor after the primary catalyst (some systems use an AF ratio sensor after the catalyst) (FIGURE 9-22). The front AF sensor is primarily for AF ratio fuel trim operation. The catalyst monitor compares the AF ratio sensor signal with the post primary catalyst oxygen sensor voltage values. A catalyst that can store and release oxygen at the required levels to promote proper exhaust emission control will have a very steady value. The value may be anywhere between 0.1 and 0.9 V but will be steady, which indicates that the catalyst oxygen levels are stable. This indicates that the catalyst is functioning normally. A catalyst that is unable to maintain steady levels of oxygen will allow excess exhaust pollutants into the air and will have an unsteady voltage value. An oxygen or AF sensor reading after the catalyst that varies in sync with the PCM fuel trim varying the air-fuel ratio indicates that the catalyst is not storing and releasing oxygen properly and may be deteriorated, damaged, contaminated, or has been removed.

FIGURE 9-22 The PCM monitors the AF ratio sensor and the post catalyst oxygen sensor to determine the oxygen storage capacity of the catalyst. © Jones & Bartlett Learning.

Description The catalyst monitor runs after the oxygen sensor or AF ratio sensor monitors have completed and passed, operating normally, and will store a DTC (usually P0420) and related Mode 6 monitor test results (FIGURE 9-23). DTCs related to components that can inhibit proper cylinder combustion will not allow the catalyst monitor to run. Also, there are several enable conditions, including engine speed, closed loop operation, and others, that must be within the correct range for the catalyst monitor to run.

FIGURE 9-23 Catalyst monitor test results can be found as part of the Mode 6 test results.

© Jones & Bartlett Learning.

Catalysts can be damaged due to overheating during a misfire condition. This can overheat the honeycomb substrate causing it to melt or disintegrate. An engine that is burning engine oil due to worn piston rings or valve guides can contaminate the substrate with a coating of carbon-based soot that impairs the catalyst from functioning to reduce emissions. The catalyst can be damaged due to being struck by objects on the road, which can impair exhaust flow or break apart the catalyst substrate. Some vehicle owners remove the catalyst hoping to increase horsepower, and catalyst theft has become a problem in many areas because a used catalyst is worth money at auto recycling centers. Rather than installing a replacement, a section of exhaust pipe is installed in place of the missing catalyst.

Catalyst System Monitor DTC Cause 9-4 Diagnose catalyst system concerns.

Any time the catalyst monitor drive cycle completes, it stores Mode 6 test data. You can view this on the scan tool, and it is very helpful even if a DTC is not stored. For example, if a vehicle has failed an emissions inspection for excess exhaust emissions yet there are no DTCs, you can view the catalyst Mode 6 test results to see if the data indicate the catalyst is well within the normal range or is near the limit for setting a DTC. A catalyst monitor failed test result should not lead you to immediately condemn the catalyst (FIGURE 9-24).

FIGURE 9-24 A catalyst-related DTC indicates catalyst efficiency is outside normal limits. It does not mean the catalyst has failed. © Jones & Bartlett Learning.

The technician must verify that systems related to proper catalyst operation are all okay before replacing a catalytic converter. Systems that affect catalyst operation include the following: Exhaust leaks that can affect the AF sensor readings and/or allow outside air to enter the catalyst AF ratio sensor(s) or oxygen sensor not operating correctly EGR (if applicable) not operating correctly Excessive oil consumption that creates a buildup of carbon soot on the catalyst substrate Very rich mixtures or engine misfires that cause the catalyst substrate to overheat and melt or break apart Secondary air systems that pump air into the exhaust during closed loop operation

Any component that can affect fuel trim can also affect catalyst efficiency. Also, accurate test results rely on accurate air-fuel and oxygen sensor operation. Catalysts are expensive. Follow diagnostic trouble flow charts thoroughly and ensure that fuel trim is normal and that the related air-fuel ratio and oxygen sensors are functioning normally. An AF sensor that is not functioning correctly can put the catalyst out of balance, which will not allow it to store and release oxygen correctly. Check for evidence of oil consumption issues. Check the oil level and ask if the customer has been adding oil to the engine at a higher than normal rate. Excessive oil burning in the combustion chambers can lead to a contaminated catalyst due to the oil film coating and turning to an insulating layer of carbon on the catalyst substrate. The carbon blocks the catalyst material from reacting with the harmful exhaust gases so they exit into the air (FIGURE 9-25). The carbon can build up to the point that the catalyst clogs. The catalyst can sometimes revive if the condition is corrected and the carbon burns off the catalyst substrate. Overly rich conditions can cause the catalyst to overheat. The substrate honeycomb structure can melt into a blob of material, which can lead to a loss of power due to the exhaust restriction it creates. It can also disintegrate and blow out of the exhaust system leaving little or no material in the catalyst housing. The cause of the rich condition must be corrected before replacing the catalyst or the new catalyst will also fail. Fuel trim readings must be within normal limits. Also, a customer who has used a non-factoryapproved PCM performance-based software update could cause this condition, as it may allow too much fuel and thus raise the catalyst temperature beyond normal limits.

FIGURE 9-25 Carbon buildup and catalyst substrate overheating can lead to catalyst failure. © Jones & Bartlett Learning.

Too little or too much EGR can cause the exhaust gases to be out of balance. This can lead to a catalyst DTC, but the cause is not the catalyst. Use of the Mode 6 EGR test results can assist you in

determining if this may be the cause. Test values that are very low or very high but not enough to set an EGR monitor DTC indicate that there may be a problem, like a valve that is opening too much or the EGR flow impeded by carbon buildup and must be inspected. It is important to verify that related systems that can affect catalyst efficiency are working normally or are outside normal limits and require further inspection before condemning one or more catalytic converters. To check items to validate catalyst monitor failure, follow the steps in SKILL DRILL 9-3.

Case Study: P0420 Code on a Vehicle A 2010 Kia Rio is in for a check engine light ON concern. The technician obtains DTC P0420, catalyst efficiency exceeds thresholds. The technician views Mode 6 data with the scan tool and notes the test results on the repair order. This vehicle has a four-cylinder inline engine, so there is only one cylinder bank. The technician observes the AF ratio sensor values and the post catalyst oxygen sensor values. The AF sensor values are changing in small increments, and the post catalyst oxygen sensor is mirroring the changes. The technician snaps the throttle and observes the sensor readings. Again, the AF ratio sensor shows a rich mixture as does the oxygen sensor. It appears that the catalyst may not be operating normally. SKILL DRILL 9-3 Checking Items to Validate Catalyst Monitor Failure

1. Exhaust leaks ahead of the AF or oxygen sensors create inaccurate air-fuel ratio readings for the PCM. A failed exhaust manifold gasket, cracked exhaust manifold, or exhaust leak at a joint before the catalyst reduces catalyst efficiency. Exhaust leaks can be found by performing a smoke test of the exhaust system. Connect the smoke machine to the exhaust pipe. (If there is dual exhaust, do the bank that has the fault. If both banks have a fault, you must check both sides of the exhaust.) Check for leaks throughout the exhaust with focus on the exhaust manifold and exhaust gasket to cylinder

head areas. Leaks may present at AF or oxygen sensor mounting locations and exhaust system joints. Repair any leaks, clear the P0420 DTC, and then perform the catalyst drive cycle. Once the catalyst monitor completes, you can review the monitor test data and verify whether the catalyst is okay or may require further inspection.

2. Inspect the AF sensors for proper operation. Perform the scan tool test to test the AF sensor. This test increases and decreases injector on-time, and you can monitor AF sensor reaction to the change in the air-fuel ratio. Faulty AF sensors should be replaced because their data are used by the PCM to evaluate catalyst efficiency.

3. Inspect the oxygen sensors for proper operation. This requires the use of a digital storage oscilloscope (DSO). Most oxygen sensors are now used only in the post catalyst position, although older OBD II vehicles also used them ahead of the catalyst. Each sensor will need to be tested if there are more than one on the affected cylinder bank. Test each one separately. Test each sensor for response to a lean mixture by creating a vacuum leak. The sensor voltage should go low. Use throttle body cleaner and spray a small amount where you created the vacuum leak. The sensor should indicate a rich mixture (high voltage, above 0.75 V). Test the sensor for response time. Reconnect the vacuum hose where you created the vacuum leak and let the sensor response stabilize. Disconnect the vacuum line again and quickly snap the throttle open. Freeze the DSO screen where the oxygen sensor changed from low voltage (less than 0.25 V) and increased to over 0.75 V. The response time must be less than 100 ms (0.01 s). Replace any oxygen sensor that fails any part of the test.

4. Verify that the EGR system is functioning normally. A stuck closed EGR valve can raise NOx levels, which can affect catalyst efficiency because the catalyst is designed to work within a window of reducing NOx to nitrogen and oxygen and then oxidize fuel and carbon monoxide molecules. A stuck open EGR that is allowing a very small amount of EGR upsets the AF ratio and affects catalyst efficiency.

5. Check the oil level to determine oil consumption concerns. If it is below the add mark, check with the customer to see when the last oil change was and whether the customer has been adding oil on a regular basis. An engine that is burning oil in the combustion chamber due to worn piston rings, valve guides, or valve stem seals can create a carbon film in the

catalyst. The carbon buildup seals the catalyst metals from having contact with the various exhaust gases, and it also impedes the catalyst’s ability to store and release oxygen. This condition can set DTC P0420 and may also result in a vehicle that fails an emission test. An engine with two cylinder banks that has a P0420 DTC for only one of the two banks most likely does not have an oil consumption issue, as the wear would usually be on both cylinder banks of components. However, it may be worth inspecting the spark plugs to look for oil fouling in one of the cylinders of the affected bank.

6. Misfires that allow unburned fuel into the catalyst can damage the catalyst, as can a leaking injector that allows unburned fuel into the exhaust. The fuel can burn in the catalyst and melt the substrate. This damage requires replacing the catalyst and repairing the fault that created it. Check the misfire counts to see if one or more cylinders has misfires, although they may not be high enough to set a misfire-related DTC. 7. Secondary air systems that pump air into the exhaust cause the PCM to react as if there is a lean mixture. This may set a fuel trim too rich DTC if severe enough. The secondary air fan (air pump) should be OFF once the engine has been running for 1 to 2 minutes under most normal conditions. Verify that the pump is OFF once the vehicle has reached normal operating temperature. A pump that is still ON will need to be diagnosed for the cause. A faulty secondary air control valve (one-way valve, on some vehicles it is a check valve) can allow ambient air to enter the exhaust even if the fan is OFF. These valves can be checked using a smoke machine. With the engine OFF, connect the smoke machine to the air pump hose that connects to the check valves. There should not be any smoke coming from the exhaust when the system is OFF. If smoke is detected in the exhaust, inspect the valves and replace them if they have failed. 8. Create a repair order of your findings and review it with your instructor. Return any test equipment to its storage location. © Jones & Bartlett Learning

This vehicle does not have an EGR valve and related EGR passages. It does use VVT on the exhaust camshaft for the internal EGR effect. The technician uses the scan tool control on the VVT and notes that it does change on command. The technician checks the engine oil level and notes that it is very low. This vehicle has over 135,000 miles, so the technician asks the service advisor to contact the customer to see if the customer has been adding oil to the engine on a regular basis. The service advisor returns in a few minutes and states that the customer drives around 300 miles per week and has been adding a quart of oil about every 2 weeks. The technician does a quick check for oil leaks and does not see any evidence of a leak that would create that much oil usage. The technician removes the spark plugs and they appear original with worn electrodes and slight oil fouling. The technician performs a compression test and notes readings of 110, 108, 124, and 106. Dividing the lowest number by the highest number, 106/124 = 85.4% so there is more than a 10% difference between the highest and lowest cylinder. This is evidence of piston ring wear. The technician performs a leakdown test and notes that three of the four cylinders are in the marginal range. Only the cylinder with the highest compression reading is normal. The technician also notes that the cylinder leakage is into the crankcase area. This indicates worn rings. The technician performs one more test to completely verify what he suspects may be affecting the catalyst efficiency: carbon buildup from oil usage. The technician removes the AF sensor and uses a viewing scope to look inside the catalyst. The technician can see that the catalyst substrate is all black in color. Replacing the catalyst on this vehicle would be an expensive but temporary repair. The new catalyst would be coated with carbon over time and the catalyst efficiency DTC would set again. The customer must decide whether to renew the engine. The technician presents the findings and recommendations for the service advisor to price out and discuss with the customer.

Catalytic Converter Heat Test The catalyst can be tested for efficiency using an infrared temperature sensor (FIGURE 9-26). The catalyst temperature varies internally as the reactions take place inside it. In pure theory, the catalyst reactions absorb heat as part of the process of scrubbing the emissions from the exhaust gases. To use an infrared thermometer to test catalyst operation, follow the steps in SKILL DRILL 9-4.

FIGURE 9-26 Catalytic converters can be tested using an infrared temperature sensor. © Jones & Bartlett Learning.

Remember, you can also use the scan tool data list PIDs to view AF and oxygen sensor readings to determine if the catalyst oxygen levels are stable or abnormally fluctuating, just like the PCM software does as part of the catalyst monitor. You can also use the scan tool output commands to vary the air-fuel ratio rich and lean to see how the catalyst oxygen storing handles these changes. Remember that the catalyst is not consumed by the reactions, it just promotes them when conditions are correct. A damaged catalyst that is clogged or the substrate is broken apart will have to be replaced. TECHNICIAN TIP This test has many proponents and almost as many who state it can be inconclusive. The test is unobtrusive, so you may want to perform it as part of your overall tests to determine whether the catalytic converter requires replacement.

SKILL DRILL 9-4 Using an Infrared Thermometer to Test Catalyst Operation

1. Test-drive the vehicle to bring the catalyst up to normal operating temperature.

2. Place the vehicle on the lift.

3. Maintain engine rpm at 1500 to 2000 to maintain catalyst operation and heat load.

4. Raise the vehicle to access the catalysts.

5. Use an infrared temperature tool to measure the catalyst inlet and outlet temperatures.

SAFETY TIP Do not touch the catalyst due to its high temperature. Also, keep your hands clear of the accessory drive area since the engine is running. 6. The inlet temperature should be about 100o F higher than the outlet temperature. a. The catalyst reaction absorbs heat, so the outlet side is cooler than the inlet side. b. Perform the test on each of the catalysts on the vehicle. 7. Note your findings on a repair order and review them with your instructor. Return any tools to their storage location. © Jones & Bartlett Learning

Replacing a catalytic converter that has failed requires the following: The root cause of the failure has been corrected. A factory original catalyst can be installed. Use of an after-market catalyst may require that its performance has been verified and has an approval number that can be viewed when it is installed on the vehicle (FIGURE 9-27).

FIGURE 9-27 Aftermarket replacement catalytic converters may have to meet state standards and are identified with an approved number on the housing.

Install the new catalyst and perform a thorough test drive based on the catalyst monitor drive cycle. Once the monitor is complete, review the Mode 6 test results and ensure that the test data are within the normal range. TECHNICIAN TIP A shop tech who has use of a five-gas emission analyzer can use the analyzer to view exhaust emission data to assist in catalyst operation. This can be helpful in determining whether the catalyst is operating as designed or has been damaged. The technician can also compare before and after repair emission readings to ensure the catalyst and other systems are operating within normal limits.

WRAP-UP Ready for Review Noncontinuous monitors allow for PCM observation of emission control devices that do not operate all the time. The EGR valve allows burnt exhaust gas to be reintroduced into the combustion chamber to help decrease the temperature of the exhaust gases. The EGR can be operated in two ways: electronic and vacuum. Electronic EGR is highly precise and can provide feedback to the PCM about the operation of the EGR valve. Vacuum is the simplest form of EGR control, but it does not provide feedback through the vacuum line. The Delta Pressure Feedback EGR (DPFE) sensor measures the flow of exhaust gases when the vacuum EGR valve operates so the PCM can determine whether the EGR valve is operating properly. The catalytic converter (CAT) helps convert the exhaust fumes into harmless CO2 and H2O. Using a heavy metal catalyst, the CAT converts the engine exhaust output on a molecular level to harmless fumes out the tailpipe. The PCM monitors the CAT conversion process with HO2 sensors, which are located before and after the CAT. The HO2 sensors measure the oxygen content of the fumes before and after to do a comparison so it can measure the effectiveness of the CAT. If the CAT is not effective, the PCM can set a DTC alerting the technician to the CAT failure. The catalyst monitor is a noncontinuous monitor because it needs certain conditions to be correct before it runs.

Key Terms Atkinson cycle engine An engine cycle that uses a longer effective exhaust stroke than intake stroke to reduce exhaust emissions. This type of engine is widely used in hybrid electric vehicles. Delta Pressure Feedback EGR (DPFE) sensor A sensor for pressure differential within an exhaust system to verify EGR operation. Duty cycle The percentage of one period of time in which the circuit is powered ON. EGR valve position sensors A sensor located in the EGR valve that monitors the position of pintle within the component. The sensor may be analog or digital. Exhaust back pressure Pressure buildup in the exhaust system related to restriction of flow of exhaust fumes through the system. Exhaust gas recirculation (EGR) A valve that allows a controlled amount of exhaust gas into the intake manifold during a certain period of engine operation. Used to lower nitrogen oxide exhaust emissions. NOx A sensor that detects oxygen ions originating from nitric oxide (NOx) from among the other oxygen ions present in the exhaust gas. Stoichiometric ratio The optimum ratio of air to fuel for combustion—14.7 parts air to 1 part fuel by weight.

Review Questions 1. Review the catalyst monitor test shown. How long does the catalyst test monitor the data in this vehicle example? a. 10 seconds b. 60 seconds c. 360 seconds d. 15 minutes or less

© Jones & Bartlett Learning.

Description Description 2. Enabling conditions for DTC P041900, insufficient EGR flow detected, are shown. All of the following will inhibit this monitor from running EXCEPT: a. a fuel system DTC. b. the engine running at 2150 rpm. c. the vehicle traveling at 72 mph. d. IAT at 12o F.

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3. All of the following could affect a catalyst monitor test EXCEPT: a. a contaminated MAF sensor. b. an exhaust manifold to cylinder head air leak. c. low oil pressure to the VVT control valves. d. a P0456 EVAP system large leak detected. 4. The catalyst monitor relies on which sensors to determine catalyst monitor data? a. Air-fuel ratio sensors and/or oxygen sensors b. CKP and oxygen sensors c. ECT and air-fuel ratio sensors d. MAF and air-fuel ratio sensors 5. Which component prevents exhaust gas from entering the combustion chamber? a. One-way air check valve b. Exhaust back pressure relief valve c. VVT on the intake camshaft d. EGR valve 6. The catalyst functions to minimize all of the following harmful exhaust gases EXCEPT: a. carbon monoxide. b. carbon dioxide. c. hydrocarbons. d. oxides of nitrogen. 7. The EGR system reduces which of the following emissions? a. Carbon monoxide molecules b. Hydrocarbon molecules c. Oxide of nitrogen (NOx) molecules d. Carbon dioxide molecules 8. Which of the following sensors is usually related to the EGR monitor?

a. MAP b. ECT c. CKP d. IAT 9. A failed catalyst may be indicated by which of the following? a. Short-term and long-term fuel trim value decrease b. B1S1 and B1S2 AF or HO2S values almost identical c. B1S1 HO2S values fluctuate between 0.13 and 0.87 V at a steady 1500 rpm d. B1S2 HO2S values fluctuate between 0.38 and 0.42 V at a steady 1500 rpm 10. The oxygen sensor heater test result shown below indicates this test is which of the following? a. Fail b. Monitor incomplete c. Pass d. Inconclusive

ASE Technician A/Technician B Style Questions 1. Technician A says the EGR monitor checks for EGR flow. Technician B says the EGR monitor checks for EGR valve position for all types of EGR valves. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B 2. Two technicians are discussing the EGR monitor test results shown below. Technician A says the test value indicates this monitor test value is too high, the monitor result will be Fail, and a DTC will store. Technician B says the test is monitoring the pressure change when the EGR valve is opened to verify the passages are not plugged or the valve is not functioning. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B

3. Technician A says a noncontinuous monitor status of Complete indicates the monitor has passed all related tests. Technician B says a noncontinuous monitor status of Complete indicates related test data values are stored. Who is correct?ble a catalyst DTC may be stored. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B

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Description 4. Refer to the EGR monitor strategy shown below. Technician A says the MIL illuminates as soon as an EGR flow fault is detected. Technician B says the EGR system is tested one time for each driving cycle. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B 5. Refer to the EGR monitor information shown below. Technician A says this monitor test will not run if engine rpm is above 2000. Technician B says this monitor test runs during fuel cut. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B

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6. Two technicians are discussing the catalyst monitor test results shown below. Technician A says the test is a Pass result. Technician B says this monitor will not run if there is an air-fuel ratio sensor fault. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B

© Jones & Bartlett Learning.

Description 7. Refer to the EGR monitor information shown below. Technician A says an EGR valve that is stuck closed could cause the monitor test to fail. Technician B says the monitor must fail on two trips before the MIL turns ON. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B 8. Technician A says the noncontinuous monitors will all run on every drive cycle. Technician B says EGR and catalyst monitor testing occur when the engine is running but the vehicle is not moving. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B 9. Technician A says the EGR and catalyst monitors will run even if there is a DTC for an ECT fault. Technician B says the EGR and catalyst monitors both use the post catalyst (B1S2) oxygen sensor to determine system operation. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B 10. Technician A says Mode 6 monitor test results can be viewed only if the monitor test has failed. Technician B says a Mode 6 test monitor that is complete indicates the system has passed the monitor test. Who is correct? a. Technician A

b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B

© Jones & Bartlett Learning.

CHAPTER 10

Noncontinuous Monitors: Evaporative Emissions System Diagnosis LEARNING OBJECTIVES After studying this chapter, you should be able to: 10-1 Analyze the operation of the evaporative emissions system. 10-2 Analyze EVAP system monitor test results. 10-3 Analyze EVAP purge flow. 10-4 Diagnose evaporative emission system concerns.

YOU ARE THE AUTOMOTIVE TECHNICIAN A check engine light concern leads you, the technician, to DTC P0456, evaporative emissions system small leak detected. Which of the following will most likely be required for your diagnosis? View KOER data list parameters. Review DTC-related service information. View OBD II Mode 5 data. View OBD II Mode 6 data. Review freeze frame data. Inspect EVAP system for leaks. Perform MAP and/or MAF inspection and related testing. Check for an exhaust leak. Inspect HO2S or AF ratio sensors. Verify proper fuel pressure.

Introduction OBD II EVAP codes are common and often fall into two common diagnostic categories. The first is a customer who forgets to install or tighten the fuel cap. This can cause an EVAP leak-related diagnostic trouble code (DTC) to store, or on some vehicles, illuminate an instrument cluster icon that looks like a fuel cap, reminding the owner to install or tighten the fuel cap. The second is an EVAP system fault. This may be a system leak, large or small, or may be a purge flow fault. Your understanding of the various EVAP system designs and related components is critical to applying the strategy-based diagnostic process, identifying the cause of the fault, and then making the repair.

Evaporative Emissions System Overview 10-1 Analyze the operation of the evaporative emissions system.

The evaporative emissions system (EVAP) functions to store fuel tank hydrocarbon (HC) vapors in a storage container and then draw those vapors into the intake manifold at the appropriate time. Drawing the vapors from the storage container is called purging the EVAP system. The EVAP system functions as follows: HC vapor from the vehicle fuel tank must be vented as the fuel expands due to temperature changes. HC vapor that enters the atmosphere reacts with sunlight and is a major component of photochemical smog, so it must be stored to prevent this. EVAP systems were required on California vehicles beginning in 1970, and in the rest of the country in 1971. HC vapor is stored in the EVAP vapor storage canister: The canister is filled with activated charcoal, similar to a fish tank filter. The HC molecules are attracted to the charcoal, similar to when you rub a balloon on your shirt and the static electricity charge holds the balloon in place. OBD II EVAP systems use a vent valve located on the fuel tank vent line after the storage canister and is used to seal the system during the monitor leak test. A powertrain control module (PCM)–controlled purge control valve connects the storage canister to the intake manifold and allows the HC vapors from the canister to mix with the intake air for burning during the combustion process. OBD II monitoring for EVAP system vapor leaks and correct purge flow have been required since 1996. Non-OBD II EVAP systems may have to be inspected for leaks (and repaired if they fail) as part of state or local emissions tests.

OBD II EVAP System Operation OBD II EVAP systems are monitored for vapor leaks, and that system can purge the stored vapor from the canister to the intake manifold. Purging allows the HC vapors to mix with the incoming air. The PCM decreases injector on-time during EVAP purge to maintain the target air-fuel ratio. Feedback from the airfuel ratio sensor is used by the fuel monitor to provide adjustments—viewed on the scan tool parameter ID (PID) data as short- and long-term fuel trim. This allows the PCM to achieve the best air-fuel ratio for current engine operating conditions and related EVAP HC vapor. The EVAP leak monitor requires that the system is sealed during the monitor test (FIGURE 10-1). Sealing the EVAP is done through use of a nonvented fuel cap, a PCM-controlled purge control valve, and a PCM-controlled canister vent valve.

FIGURE 10-1 The EVAP system stores hydrocarbon vapors from the fuel tank so they are not released into the atmosphere. Once the engine meets certain criteria, the hydrocarbons are reintroduced into the combustion chamber. © Jones & Bartlett Learning.

TECHNICIAN TIP Control valves such as the purge and vent valves are inductors. Inductors can fail open or shorted. A failed open inductor (the coil winding inside the component that creates the magnetic field) will not damage an engine control unit (ECU), as there is no current in the circuit. A shorted coil increases circuit current and can damage the control circuit inside the PCM. This is indicated when the PCM is unable to provide an output duty cycle signal to the purge valve or turn the vent valve ON. An ohms test can verify that the coil is shorted. Always replace the PCM and the related inductive component when a short is the cause. Replacing only the PCM will allow the failed shorted coil in the purge or vent valve to damage the new PCM, creating an expensive comeback situation.

EVAP System Nonvented Fuel Cap

The fuel cap is nonvented so it can seal the fuel filler neck and the on-board refueling vapor recovery (ORVR) system hoses. Some vehicles do not have a fuel cap, instead using a fuel filler neck that incorporates a valve that opens when the gas pump nozzle is inserted and reseals when it is removed (FIGURE 10-2).

FIGURE 10-2 Some vehicles do not use a fuel cap, instead using a filler neck that opens when the fuel nozzle is inserted during refueling. © Jones & Bartlett Learning.

EVAP System Purge Valve The EVAP system is sealed by the purge valve on the engine side (FIGURE 10-3). The purge valve is usually located near or on the intake manifold. Most purge valves have two vapor hose connections. One hose connects to the EVAP canister. There is usually a metal pipe that connects the purge control valve hose to another section of hose that then connects the metal pipe to the EVAP vapor storage canister. The other hose connects the control valve vapor path to the intake manifold intake air stream, usually before the throttle body to prevent a high vacuum load on the EVAP system during purge operation. When the purge valve is OFF, it is closed so no vapors from the vapor canister enter the engine. At appropriate times, usually after engine warm-up and the fuel system is in closed loop control, the PCM duty cycles the purge control valve to modulate the rate of HC vapor purge from the storage canister. The purge valve duty cycle percent may be indicated in the Mode 1 PID data, or it may only show that the purge valve is active (ON) or inactive (OFF).

FIGURE 10-3 The purge control valve is usually ground controlled. You can view the purge duty cycle using a DMM or a DSO by

connecting the positive lead to the purge control valve control signal and the negative lead to an engine ground point. © Jones & Bartlett Learning.

Description Purge valve duty cycle can be monitored using the duty cycle function of your digital multimeter (DMM) or a digital storage oscilloscope (DSO). Connect the positive test lead to the control pin (usually the ground side of the purge circuit) (FIGURE 10-4) and the negative test lead to ground. Set the DMM to measure duty cycle to view the percent value. Most manufacturer and some generic scan tools allow the technician to operate the purge control valve using Mode 8 output control. This allows the technician to verify PCM control of the control valve on demand as part of system and component diagnosis.

FIGURE 10-4 The EVAP purge valve is usually located on or near the intake manifold. © Jones & Bartlett Learning.

The DSO will display the duty cycle control square wave. Most DSOs offer a duty cycle measurement to be displayed along with the waveform (FIGURE 10-5). To test the EVAP system purge control valve, follow the steps in SKILL DRILL 10-1.

FIGURE 10-5 Most DSOs offer measurements such as duty cycle to be added to the display. Courtesy of Pico Technology Ltd.

SKILL DRILL 10-1 Testing the EVAP System Purge Control Valve

1. Obtain a DMM and/or DSO, a scan tool, vacuum pump, and assigned hand tools from your instructor. 2. Reference the related EVAP purge control valve, including inspection procedure, wiring diagram, and whether the purge control valve on your vehicle can be controlled using the output/active test Mode 8 function of your scan tool. 3. Identify the control side of the control valve circuit. This is the portion of the circuit that connects to the PCM. It is usually on the control valve ground path, though there can be source controlled circuits.

4. Connect the DMM or DSO positive lead to the control side of the circuit at the purge control valve using an appropriate back probe tool. Connect the negative lead to engine ground. 5. Connect the scan tool to the vehicle and turn the ignition ON, engine OFF. Access Mode 8 output state control/active test and the purge control valve from the list of available items. Activate the control valve. You should hear the control valve operating—usually a faint ticking sound.

6. Set the DMM to measure duty cycle and the value should display in percent (%) on the screen. Using a DSO, set the voltage scale appropriately (the OFF voltage is source voltage). You can use the auto setting for the time scale or select 100 ms as a starting point. The DSO will display the waveform. Many DSOs allow you to add a measurement such as duty cycle. Select this if applicable and duty cycle percent will also display with the waveform. Review your test results with your instructor.

7. The DMM duty cycle and DSO wave form validate PCM control of the purge control valve. The purge control valve making a ticking sound validates that it is cycling. If it is not cycling, there may be a fault with the control valve. Turn the Mode 8 active test OFF.

8. The purge control valve can be checked for a resistance value to validate that the control valve is okay. Turn the ignition OFF. Disconnect the purge control valve connector. Using appropriate test connectors, measure the resistance of the purge control valve coil and compare to service information specifications. Reconnect the purge control valve connector and review your findings with your instructor. 9. You can also verify that the purge control valve opens and closes properly. Connect a vacuum pump to the purge control valve hose that connects to the intake manifold. Apply vacuum with the control valve OFF. The vacuum pump should hold a steady vacuum. If it does not, the valve may be stuck open. Turn the ignition ON and use the scan tool (if applicable; if not, you can provide a ground path to the control valve if it is ground controlled and it will turn ON) to activate the control valve. The applied vacuum should drop to 0, indicating the valve has opened. 10. This completes the purge control valve skill drill. Return all tools to their storage location. Verify all electrical connectors are connected and the ignition is OFF. © Jones & Bartlett Learning

EVAP System Vent Valve A PCM-controlled vent valve is used on the EVAP storage canister vent line. This vent line is what allows the fuel tank to maintain a pressure that is nearly the same as atmospheric pressure. The vent valve is located after the storage canister. The vent valve is normally open so the fuel vapor area in the fuel tank can expand or contract depending on ambient air temperature and barometric pressure changes. As the

temperature increases, fuel vapors expand and enter the storage canister. The HC molecules cling to the activated charcoal, and any other gases escape to the atmosphere. When the ambient temperature cools, the space inside the tank contracts and ambient air can enter the system to keep tank pressure equal to ambient pressure. The ambient air that enters the system also carries some of the HC molecules back into the tank. This process helps prevent the storage canister from totally filling with HC vapor. The canister size and related amount of charcoal storage are based on the size of the fuel tank (FIGURE 10-6). The vent valve can be inspected for an open or short using a DMM on the ohms setting. A short in the vent valve solenoid may damage the PCM output control circuit, requiring replacement of both components. Vent valves that are not integral to the EVAP storage canister can usually be tested to verify that they are open when OFF and closed when energized. This can be accomplished using one or more of the following methods:

FIGURE 10-6 The EVAP canister is usually located under the vehicle near the fuel tank. © Jones & Bartlett Learning.

Run the EVAP monitor vent valve test using Mode 8 (may not be available on early OBD II vehicles). Use a vacuum pump to verify that the valve seals when energized. Use a smoke machine to verify that the vent valve is open when OFF and closed when energized. Many manufacturers offer an EVAP leak test that is accessed from the Mode 8 output state/active test menu. The leak test closes the vent valve and then duty cycles the purge control valve to apply vacuum to the EVAP system (some systems apply a small amount of pressure rather than vacuum). A vent valve that does not close will result in little or no pressure change during the test. The fuel tank pressure sensor will show little or no PID data change. You can then verify whether the vent valve is at fault by using the smoke machine. Connect the machine to the EVAP test port or to the purge line that connects

to the EVAP storage canister at the purge valve. Use the scan tool to close the vent valve. (You can also use a jumper lead to ground on the vent valve circuit if the scan tool test is not available.) Smoke emitting from the vent valve indicates it is not closed and may have failed. Some vent valves can be replaced, whereas others are integrated into the EVAP storage canister. These may require replacing the EVAP storage canister assembly.

EVAP Monitor Test Results Analysis 10-2 Analyze EVAP system monitor test results.

The EVAP leak monitor may be handled for most vehicles in one of three methods: Applying a vacuum to the EVAP system when the engine is running Applying pressure or vacuum to the EVAP system using a leak detection pump (LDP) Sealing the EVAP system after engine shutdown and monitoring natural vacuum level The leak monitor functions to determine that the EVAP canister, related hoses, and fuel cap seal are all operating normally. Most leak monitors can determine whether a small leak is detected or a large leak is present. A leak as small as 0.1 mm can be detected in some systems. A large leak is usually related to a disconnected EVAP-related hose, a loose or missing fuel filler cap, or a very damaged component, such as a torn hose or cracked vapor canister. TECHNICIAN TIP Some vehicles offer a fuel cap indicator light if the fuel cap is left off or loose. This can eliminate the need for a visit to an automotive repair facility for a MIL ON condition that was caused by a loose fuel cap.

EVAP Vacuum-Type Leak Monitor The vacuum-type EVAP leak monitor was one of the first types applied to vehicles when OBD II went into effect in 1996. This is an easy test to perform by the PCM and is done while the engine is running. The test runs as follows: The vent valve is closed to seal the system from outside air. The purge valve is duty cycled to apply engine vacuum to the EVAP system. A fuel tank pressure sensor, similar to a MAP sensor but with a very narrow pressure measurement range, detects small pressure changes in the EVAP system (FIGURE 10-7).

FIGURE 10-7 The fuel tank pressure (FTP) sensor operates like a MAP sensor with a very narrow pressure range, and is located on the fuel tank. © Jones & Bartlett Learning.

The EVAP system is put under a very small vacuum. A properly functioning EVAP system quickly allows negative pressure to build and reach the level that indicates the system is free from leaks. A small leak is indicated when negative pressure builds but is not able to reach the pass threshold value, or it may take too long to reach the value. A large leak is indicated when very little or no change in pressure occurs during the leak test. A small leak usually sets DTC P0456 and a large leak stores DTC P0455 for most vehicles. Some vehicles may use other DTC codes, and there are DTCs for related components, including the vent valve and fuel tank pressure sensor; however, these are usually part of the component monitor. The EVAP monitor usually requires two consecutive trip failures for a DTC to store. Every time the EVAP monitor runs and completes, Mode 6 test data stores. The data can be useful for diagnosing and verifying your repair work. TECHNICIAN TIP This type of EVAP test is not favored by the Environmental Protection Agency (EPA) and California Air Resources Board (CARB) since a leak at a fitting, where a pipe joins a hose, can be eliminated when the vacuum helps seal the connection. Most EVAP monitors use a fuel tank pressure (FTP) sensor, similar to a MAP sensor. The EVAP fuel tank pressure sensor has a very narrow range compared to a MAP sensor, but the construction is the same. The sensor uses three wires, one is a 5-V reference, one is ground, and one is for the signal to the PCM (FIGURE 10-8). To diagnose an FTP sensor, follow the

steps in SKILL DRILL 10-2.

FIGURE 10-8 The fuel tank pressure sensor is similar to a three-wire MAP sensor, though the FTP is calibrated to measure pressures in a very narrow range to detect EVAP system leaks. © Jones & Bartlett Learning.

Description SKILL DRILL 10-2 Diagnosing a Fuel Tank Pressure Sensor

1. Obtain your assigned vehicle, scan tool, DMM, and applicable hand tools from your instructor. 2. Obtain the FTP sensor wiring diagram and inspection procedure.

3. Access the FTP sensor. It may be part of the EVAP storage canister or part of the fuel pump module. Most vehicles offer an access panel under the rear seat cushion. Trucks and SUVs may require dropping the fuel tank to access the fuel pump module.

4. Identify the wires at the FTP sensor. Turn the ignition ON. Use the DMM to verify the 5-V reference, signal voltage, and that the ground has less than 50-mV drop to a known good ground. Review your results with your instructor.

5. Connect the DMM to the FTP signal wire to monitor voltage. Use the scan tool to run the EVAP leak monitor test. This will place a negative pressure on the EVAP system and fuel tank, causing the FTP signal value to decrease. Note: Some sensors may be removable from the pump module or EVAP storage canister. It may be possible to use a handheld vacuum pump to verify that the FTP reacts to a change in pressure. Review your results with your instructor.

6. Turn the ignition OFF. Refer to the service information FTP inspection procedure. Some sensors can be checked for a resistance value. If this is the case, measure the resistance per the inspection procedure and compare your results to the specifications. Review your results with your instructor. 7. A sensor that does not react to a change in pressure will need to be replaced. A reference voltage, ground, or signal wiring that has more than 50-mV drop between the sensor and PCM indicates resistance in the wiring that will affect the FTP output signal. Check connectors and the wiring harness for damage or corrosion. Review your findings with your instructor. 8. Once all tests are complete, reinstall any parts removed and return tools to their storage location. © Jones & Bartlett Learning

The EVAP monitor usually requires a moderate temperate range to run. Temperatures much below freezing and above 90o F are usually out of range for performing the engine running vacuum test. This is important to note, as there may be times of the year, based on the type of weather, where the EVAP monitor may not run for an extended period of time. This can make the repair of EVAP-related DTCs seasonal in areas with extended cold or very warm temperatures, such as in Maine in the winter or in southern Arizona in the summer.

Leak Detection Pump Type EVAP Monitor

Many current vehicles use a leak detection pump to test the EVAP system for leaks (FIGURE 10-9). Chrysler and Mitsubishi began to use a leak detection pump EVAP test in 1994. Some systems apply pressure to the system and others apply a small vacuum. These vehicles incorporate a small pump module assembly mounted on or near the EVAP canister.

FIGURE 10-9 Many EVAP systems currently use a leak detection pump to test for system leaks. © Jones & Bartlett Learning.

Description The positive pressure-type system covered here is based on the Chrysler/Mitsubishi system used when OBD II was introduced (FIGURE 10-10). This system uses a small pump assembly that uses engine vacuum for pump operation and operates as follows:

FIGURE 10-10 The Chrysler-style leak detection pump uses engine vacuum to operate the pump and apply a very small amount of pressure to the sealed EVAP system. © Jones & Bartlett Learning.

Description Description The Chrysler/Mitsubishi leak detection pump-type test begins after a cold soak engine start. Engine vacuum is applied to a sealed chamber to move a spring-loaded diaphragm and close the vent valve. The vent valve and purge valve remain closed during the leak monitor test. The PCM turns the control valve ON and OFF to cycle the pump diaphragm up and down to pressurize the EVAP system. A control switch detects the movement of the diaphragm, an input to the PCM. The pump diaphragm spring is calibrated to about 1″ of water pressure (0.44 psi) and it stops moving once this pressure is reached in the EVAP system. The PCM monitors input from the control switch for how fast the diaphragm is moving and, once stopped, how long it remains stopped as part of the EVAP leak test. A diaphragm that keeps moving indicates a large leak. Movement that becomes slow, but takes too long to reach a stopped position, or if once stopped, starts moving again after a very short time period, indicates a small

leak. Once the EVAP leak monitor completes, the vent valve is opened and pressure releases and the monitor results are stored in the Mode 6 test data. The vacuum-type system described is based on the Toyota system used on many of its vehicles. This system uses an electrically operated vacuum pump that is located in the vapor canister assembly. The test functions as follows after the engine is OFF for several hours (FIGURE 10-11):

FIGURE 10-11 This EVAP system uses a leak detection pump to apply vacuum to the system to determine if any leaks are present. © Jones & Bartlett Learning.

Description Test A: Measure atmospheric pressure using the canister pressure sensor. Test B: The leak detection pump valve moves to open a fixed orifice (vacuum resistance) to calibrate the values and ensure the system is functioning normally. Test C: The vent valve turns on to seal the system, and the pump operates to create a negative pressure in the EVAP system. This part of the test is where the system can pass the test or set a small or large leak DTC. Test D: The purge valve opens and normally will create a quick increase back to atmospheric pressure, indicating the purge valve operates normally.

Test E: The system takes one more reference pressure, a repeat of part B, to ensure test results are accurate. This test will not run if the ambient temperature, measured using the intake air temperature data, is below 40o F or higher than 105o F. Many manufacturers use an LDP-type EVAP monitor. The positive pressure type is usually preferred by the emissions regulating agencies. A positive pressure test is more likely to fail a system for a leak at a fitting, especially where a hose attaches to a fitting, like the vacuum hose on the purge valve from the metal purge line coming from the vapor canister. The negative pressure (vacuum) LDP can actually seal a small leak at fitting during the test, though this is not common enough for these types of systems to be abandoned. They are still in use on many vehicles. The related service information will detail LDP operation and whether it is a positive or negative pressure system.

Engine OFF Natural Vacuum EVAP Leak Detection The engine OFF natural vacuum (EONV) EVAP leak test does not rely on a vacuum pump or an engine vacuum. This test is used on many Ford and Honda vehicles as well as others. The system is set up like the engine vacuum–based EVAP test and uses a fuel tank pressure sensor. This test does not use the purge valve to place a vacuum on the system. Instead, this test takes advantage of the natural action of the fuel tank absorbing heat during the day and from driving due to exhaust heat transfer to the fuel in the tank. The EONV test runs after the vehicle is parked and the engine is OFF. The PCM monitors ambient temperature; once the temperature has dropped enough, it will begin the test sequence. The PCM closes the vent valve to seal the EVAP system. The PCM then monitors the fuel tank pressure sensor for a drop in pressure as the fuel cools overnight and creates a negative pressure in the EVAP system. A large leak is detected if there is little or no pressure drop indicated from the take pressure sensor data. A small leak is indicated if the pressure drops but does not reach system okay (pass) threshold levels. It is not uncommon for this test to take several hours to complete. This test cannot run when ambient temperatures remain high in the evening, around 100o F or higher, or if it is too cold. TECHNICIAN TIP Some vehicles operate the purge valve and then look for a change in air-fuel ratio or oxygen sensor signals that indicate a rich condition due to the hydrocarbon vapors being added to the intake manifold air charge. Refer to the service information for your vehicle to determine actual purge monitor operating parameters.

EVAP Purge Flow Monitor Analysis 10-3 Analyze EVAP purge flow.

The vent valve allows fresh air to enter the vapor canister during vapor purging, and it allows air to enter or exit from the tank as the ambient temperature causes changes in vapor pressure in the fuel tank. The activated charcoal in the vapor tank has an electrical charge that attracts and holds the hydrocarbon vapors to the outer surface of the charcoal. During purge, fresh air is drawn in through the vent valve. The movement of the air dislodges the hydrocarbon molecules from the charcoal and they are drawn into the intake manifold through the open purge valve. The EVAP system monitor includes a purge test to verify that the purge valve functions to transfer the stored HC vapors from the storage canister to the engine for burning in the cylinders during engine operation. EVAP purge occurs as follows: The vent valve remains open. The PCM determines that driving conditions support the addition of EVAP vapors to be introduced into the intake manifold. The PCM uses duty cycle control to open the purge valve and precisely control the amount of purge vapor that enters the intake manifold. Purge continues at varying duty cycle values during vehicle operation. The EVAP purge flow monitor performs a test to verify the purge flow is present (FIGURE 10-12). This example performs a very simple two-step test:

FIGURE 10-12 EVAP purge flow is also monitored as part of the EVAP monitor test.

© Jones & Bartlett Learning.

Description Step 1: The purge valve is opened fully and the PCM monitors the FTP sensor for any drop in pressure. A small pressure drop indicates that the purge valve opened and there is a large flow of vapor to the engine that is measurable by the FTP and completes the test. If no pressure drop is measured by the FTP, the monitor continues to step 2. Step 2: When no pressure drop is detected during step 1, the PCM then commands the vent valve closed to seal the system. If a pressure drop occurs, this indicates the purge valve is operating and the test passes. If no pressure drop occurs, this indicates the purge valve is not opening and the test completes with a failed result. This example requires two consecutive trip failures to set a DTC.

EVAP System Faults and Related Diagnostic and Repair Procedures 10-4 Diagnose evaporative emission system concerns.

The EVAP system can at first seem very difficult to diagnose (FIGURE 10-13). Much of this is because technicians either try to shortcut the diagnostic process and go straight to parts replacement, such as a fuel cap or vent valve, or they fail to follow the strategic diagnostic process and integrate the service information flow chart for step-by-step DTC diagnosis. Most EVAP faults are related to one or more of the following:

FIGURE 10-13 EVAP system diagnosis often involves using a smoke machine to isolate the cause of leak-related DTC. © Jones & Bartlett Learning.

Damaged or missing fuel cap seal Damaged vapor hose or line Fuel tank fuel pump module seal or loose lock ring

Vent valve fault Purge valve fault Canister damage Leak detection pump fault, if equipped Fuel tank pressure sensor fault Diagnosis tools include the scan tool, DMM, and smoke machine with nitrogen supply tank (FIGURE 10-14).

FIGURE 10-14 The smoke machine assists in finding leaks in the EVAP system. © Jones & Bartlett Learning.

SAFETY TIP Do not use shop air when pressurizing the smoke machine for a leak test. Shop air introduces oxygen into the fuel tank, which can create an explosive mixture with the fuel vapor. A spark from the fuel pump or fuel level sensor circuits inside the fuel tank could cause a small explosion that sprays burning gasoline all over the shop. Use nitrogen to pressurize the smoke machine. This will eliminate this hazard.

Case Study: Work through a P0440 Code on a Vehicle Step by Step

Fuel systems should be tested with a smoke machine connected to a nitrogen tank, since introducing shop air into the fuel tank could lead to a fire or explosion from an ignition source, such as the fuel pump. Nitrogen is an inert (noncombustible) gas and is safe to use for smoke-based leak identification. The smoke usually has a dye in it so you can use an ultraviolet light to help locate the leak. To use a smoke machine to find an EVAP leak, follow the steps in SKILL DRILL 10-3. TECHNICIAN TIP If a purge flow issue is being diagnosed, be sure to smoke test the purge valve and the hose that connects to the intake manifold, as this hose may have a leak, not fit properly, or in rare cases be blocked.

SKILL DRILL 10-3 Using a Smoke Machine to Find an EVAP Leak

1. Connect the smoke machine to the system. Usually this can be done at the purge control valve line that connects to the vapor canister.

2. Use the scan tool active test to close the vent valve.

3. Verify the fuel cap is tight and leave the fuel door open (if equipped, as some vehicles use a capless fuel filler neck and do not have a fuel cap).

4. Turn on the smoke machine and open the nitrogen tank to no more than 20 to 40 psi.

5. Use the ultraviolet light to check for leaks. a. Note: Some smoke machines have a flow gauge. The gauge indicates flow of smoke into the system. The gauge ball will be very close to or at 0 of no leak is present.

6. When the leak is found, turn OFF the smoke machine.

7. Repair the source of the leak.

8. Recheck with the smoke machine to ensure that the leak is repaired.

9. Use the scan tool active test to run the EVAP leak check monitor, if applicable, and verify the test completes and passes. © Jones & Bartlett Learning

Use of the scan tool, smoke machine, and following the service manual diagnostics will lead you to the cause of the concern. Shortcutting the process, especially with the EVAP system, often leads to a customer comeback. The FTP sensor is tested in the same manner as a MAP sensor and is covered in Chapter 3 of this text. The vent and purge control valve testing include inspecting the coil for correct resistance. If okay, check that system voltage is present and that the PCM ground control functions when using the applicable scan tool output command test (FIGURE 10-15). The scan tool also offers PID data for the EVAP FTP sensor, vent control valve, and purge control valve ON or OFF status. Many manufacturers recognize that the EVAP monitor can be difficult to run so they offer a scan tool-activated EVAP monitor test, usually located as part of the scan tool special test menu. Following the strategic diagnostic process allows you to isolate the cause of an EVAP monitor DTC accurately and efficiently.

FIGURE 10-15 The scan tool offers EVAP tests, including PID FTP sensor and vent and purge valve command status. © Jones & Bartlett Learning.

Fuel Cap Testing The fuel cap can cause an EVAP leak DTC. There is a seal on the cap near the thread area so that it seals against the filler neck. This seal can stretch or tear over time and allow fuel vapors to escape into the air. This failure can cause an EVAP leak monitor test to fail and set a small or large leak DTC. A visual inspection is usually all that is required to verify seal condition. More difficult to diagnose are internal cap faults or cap damage that prevents the cap from sealing properly. The use of a smoke machine may be able to isolate the cause of the fault to the cap. A shop that performs emissions tests that include testing the fuel cap for leaks can use the cap check function of the emissions analyzer to test a fuel cap for a leak. A fuel cap leak check tool is also available for this purpose. It should be noted that this tool costs approximately $1000. A repair facility that does a great deal of emissions failure diagnosis or EVAP leak diagnosis may find this tool worthwhile, especially when a smoke test cannot isolate the fuel cap as the cause of the fault.

WRAP-UP Ready for Review The EVAP system allows for the recapture of fuel fumes so that they are not released into the atmosphere. Most EVAP systems use a purge solenoid and vent valve to seal the system and when commanded put the system into a negative pressure environment. The FTP sensor is used to measure how much vacuum is present in the system, and the PCM uses this sensor to verify the integrity of the system. The EVAP system operates only under certain conditions based on the fuel level in the tank, engine temperature, and ambient temperature to determine its needs to the EVAP monitor. LDP systems use a vacuum pump to generate the negative pressure within the system so the PCM can monitor the decay within the system to verify integrity. ENOV systems use the laws of physics to determine the pressure change within the system after the vehicle has cooled down. A smoke machine is used to generate smoke that is then put into the system to visually see a leak that is present. Some vehicles allow a service bay test that will use a scan tool to force the PCM to run the EVAP monitor while the vehicle is in the service bay. Capturing the fuel fumes and reintroducing them into the engine allows the engine to burn the fumes without releasing them into the environment.

Key Terms Canister vent valve A solenoid that allows fresh air to enter the evaporative system during a purge event. Also used for an evaporative system monitoring test. Engine OFF natural vacuum (EONV) EVAP leak test A test that runs after the vehicle is parked and the engine is OFF. The PCM monitors ambient temperature; once the temperature has dropped enough, it will begin the test sequence. The PCM closes the vent valve to seal the EVAP system. The PCM then monitors the fuel tank pressure sensor for a drop in pressure as the fuel cools overnight and creates a negative pressure in the EVAP system. Evaporative emissions system (EVAP) A system used to capture vapors or gases from an evaporating liquid. EVAP vapor storage canister A device used to trap the fuel vapors. The fuel vapors adhere to the charcoal until the engine is started, and engine vacuum can be used to draw (purge) the vapors into the engine so that they can be burned along with the air-fuel mixture. Fuel tank pressure sensor (FTP) A sensitive pressure sensor mounted in the fuel tank or EVAP system and used to monitor the system for leaks. Leak detection pump This system uses a small pump assembly that uses engine vacuum for pump operation, and it places the system into a vacuum situation which then the PCM measures FTP decay to determine if the system has a leak. Purge control valve A valve used to control the flow of evaporative emissions from the charcoal canister to the intake manifold.

Review Questions 1. Review the EVAP monitor test shown below. How long does the leak check portion of the test take? a. 10 seconds b. 60 seconds c. 360 seconds d. 15 minutes or less

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Description 2. The monitor description for DTC P0455 and P0456 EVAP large and small leak are shown below. Which of the following is correct? a. The EVAP leak test occurs during a drive cycle. b. The engine is running at 2150 rpm. c. The purge valve is opened for 10 seconds. d. The vent valve is always open during the monitor test.

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3. The vent valve allows the EVAP system to do which of the following? a. Prevent the release of HC vapors into the atmosphere b. Control HC vapors from the storage tank into the engine during purge c. Control pressure inside the EVAP storage tank d. Close the EVAP system during leak check monitor operation 4. Most EVAP monitors use which type of sensor? a. Pressure sensor b. Position sensor c. Flow meter d. HC saturation sensor 5. The purge valve is modulated using which method to control stored HC vapors entering the intake manifold? a. One-way air check valve b. Duty cycle c. Pulse width modulation d. ON or OFF using a purge control valve relay 6. Engine OFF natural vacuum (EONV) EVAP systems can run the leak test under all of the following conditions EXCEPT: a. an ambient temperature below approximately 75º F. b. an ambient temperature above the freezing point of water. c. the vehicle operating at a steady speed above 30 mph for 3 minutes or more. d. with fuel in tank above ¼ level. 7. The EVAP canister stores which of the following emissions? a. Carbon monoxide molecules b. Hydrocarbon molecules c. Oxide of nitrogen (NOx) molecules d. Carbon dioxide molecules

8. Refer to the EVAP purge valve information shown below. Which of the following can cause DTC P0441? a. Short to ground between relay pin 2 and connector A21 pin 46 at the ECM b. Open EFI number 1 fuse c. Open between relay pin 3 and EFI-MAIN 1 fuse d. Short to ground between VSV connector C104 pin 2 and C106 pin 65 at ECM

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Description 9. The MIL may turn ON to indicate all of the following EVAP system faults EXCEPT: a. fuel cap loose. b. EVAP storage tank saturated with fuel. c. purge flow below normal level. d. a small leak present due to a damaged vapor line. 10. The EVAP system monitor may not run for all of the following EXCEPT: a. ambient temperature too high. b. fuel cap loose. c. fuel level too high. d. fuel level too low.

ASE Technician A/Technician B Style Questions 1. Technician A says the EVAP monitor checks for purge flow volume. Technician B says the EVAP monitor checks for system leaks only. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B 2. Technician A says the EVAP test will not run if the ambient temperature is too high. Technician B says some leak detection pumps create a positive pressure, some a negative pressure (vacuum). Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B 3. Refer to the scan tool information shown below. Technician A says all system tests have passed except the EVAP system, which has failed. Technician B says this vehicle does not have a secondary air system. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B

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Description 4. Refer to the EVAP monitor test information shown on the next page. Technician A says the MIL illuminates as soon as a fault is detected. Technician B says the EVAP system is tested one time for each driving cycle. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B

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Description Description 5. Refer to the EVAP monitor enabling conditions shown below. Technician A says this monitor test will not run if the ambient air temperature is above 105° F. Technician B says this monitor test runs after the vehicle has been driven for 5 minutes or more. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B

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6. Refer to the EVAP monitor test information shown below. Technician A says this monitor test will not run if the tank is full. Technician B says this monitor test will run if the ambient temperature is below freezing. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B

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Description Description 7. A technician is diagnosing a vehicle with P0456, small EVAP leak detected. Technician A says most scan tools can run an EVAP leak check with the vehicle in the shop stall. Technician B says a smoke machine connected to the exhaust system can help isolate the location of the EVAP leak. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B 8. Technician A says some EVAP tests run when the engine is OFF. Technician B says some EVAP monitor leak tests run when the engine is running. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B 9. Refer to the EVAP system monitor test results shown below. Technician A says the purge valve may

be stuck closed causing this condition. Technician B says the test limits were exceeded by 0.366 mmHg. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B

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10. Technician A says Mode 6 monitor test results may be displayed in hexadecimal format. Technician B says you must use a conversion table to identify the Test ID and Component ID. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B

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Description

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CHAPTER 11

Engine Emissions Testing and Failure Diagnosis LEARNING OBJECTIVES After studying this chapter, you should be able to: 11-1 Describe the chemistry of combustion as it relates to air-fuel mixture ratios. 11-2 Explain emissions inspection and maintenance testing methods. 11-3 List possible causes of a failed onsite emissions test.

YOU ARE THE AUTOMOTIVE TECHNICIAN A vehicle has failed an emissions test due high levels of HC and CO. Which of the following will most likely be required for your diagnosis? KOER data list parameters DTC-related service information Mode 6 data Mode 7 data Freeze frame data Inspecting for intake system air leaks Performing MAP and/or MAF inspection and related testing Checking for an exhaust leak Inspecting HO2S or A/F ratio sensors Verifying proper fuel pressure Inspecting the catalyst Determining whether an approved catalyst is installed Verifying catalyst operation

Introduction Automotive emissions testing at the consumer level has been in use since the 1970s. Automotive manufacturers and the scientific community were researching the effects of vehicle emissions by the 1960s. Water and air quality had suffered greatly because there were few regulations in place to control pollution, no matter what the source. The pollution issue gained enough traction that the Environmental Protection Agency (EPA) was created in 1970. A few years earlier, California had begun to implement laws as a means to task automotive manufacturers and other industrial emissions sources with reducing their pollution. The fuel shortages created by political situations with OPEC (Organization of the Petroleum Exporting Countries) and Iran in the 1970s, along with pollution control legislation, saddled the automotive industry with the need to reduce emissions and increase fuel economy. Areas where fuel had to be imported relied on small, economical vehicles from Europe and Japan. Meeting emissions standards allowed companies such as Datsun, Honda, Nissan, Volkswagen, and Fiat to tout their fuel mileage without the need to downsize engines or vehicles like the American manufacturers had to do during the 1970s and into the 1980s. It was an interesting and challenging time for vehicle manufacturers, but by the mid-1980s, computer controls allowed for much greater engine performance while maintaining or increasing fuel economy.

Perfect and Incomplete Combustion 11-1 Describe the chemistry of combustion as it relates to air-fuel mixture ratios.

Vehicle emissions testing is an integral part of a goal to continually improve air quality (FIGURE 11-1). Vehicle emissions testing is usually required in metropolitan areas where the EPA has determined they consistently exceed maximum limits for pollution levels related to automotive emissions. The three primary pollutants are:

FIGURE 11-1 Some locations require loaded mode testing when measuring emissions levels. These tests can measure HC, CO, and NOx emissions. Two-speed idle tests do not have the engine under load, so NOx is usually not measured. © Jones & Bartlett Learning.

1. Hydrocarbons (HC) (unburned fuel) 2. Carbon monoxide (CO) 3. Oxides of nitrogen (NOx) There are additional exhaust gasses monitored during the emissions test procedure, including oxygen (O2) and carbon dioxide (CO2). Particulate matter pollutants from gasoline-fueled vehicles are not measured under current test procedures. The simplified chemistry of combustion is HC (fuel) + O2 (air) = H2O (water) + CO2. Unfortunately, this is not yet possible in the internal combustion engine. Factors in design allow HC molecules to escape

unused during the combustion process. Fuel and air do not always mix at the ideal ratio, causing the formation of CO rather than CO2 during a rich mixture. High temperatures force nitrogen in the air to bond with oxygen and form oxides of nitrogen. This pollutant, NOx, reacts with sunlight and the air to form the brown haze in areas where pollution levels are high or the polluted air is trapped by mountains or temperature factors.

Early Efforts to Control Vehicle Emissions Air pollution was becoming a problem in large cities by the 1950s. There were no pollution controls on vehicles or other sources, such as coal-fired electrical plants and steel manufacturing. Large cities such as Los Angeles and San Francisco (California), along with New York City (New York), began to issue unhealthful air alerts. These were called smog alerts in California. The first effort to deal with the problem was to eliminate the road draft tube used on internal combustion engines. This tube allowed blowby crankcase gases to vent directly to the atmosphere through a tube connected to the crankcase that aimed the vapors at ground level (FIGURE 11-2). The HC levels from a road draft tube are extremely high, often over 1000 ppm during engine idle. With no fuel tank vapor control, no NOx control, no crankcase vapor control, and no exhaust catalysts, the air became saturated with vehicle emissions, making the pollution visible in the air.

FIGURE 11-2 The road draft tube was used through approximately 1962 and allowed crankcase vapors to vent into the air. © Jones & Bartlett Learning.

Description The first pollution control was the crankcase vapor control system, or positive crankcase ventilation system (FIGURE 11-3). Routing the vapors through a metered air leak in the PCV valve allowed the crankcase vapors to enter the intake manifold so the HC would then become part of the air-fuel mixture

instead of being released into the air. This also helped extend the life of the engine oil, as the blowby gases did not linger in the crankcase to contaminate the oil.

FIGURE 11-3 The positive crankcase ventilation system was introduced in the early 1960s and eliminated the road draft tube. © Jones & Bartlett Learning.

California began efforts to reduce vehicle emissions with the use of the smog pump in model year 1966. Most engines were required to use a belt-driven air pump that sent fresh air into the exhaust manifold(s) and promoted further burning of any remaining air-fuel mixture by adding more oxygen and using the heat of the exhaust (FIGURE 11-4). California required evaporative emissions fuel vapor storage tanks in model year 1970, and the EPA required them for the rest of the country in model year 1971.

FIGURE 11-4 The belt-driven smog pump was required on most 1966 California vehicles and helped reduce HC and CO exhaust emissions. © Jones & Bartlett Learning.

NOx controls were first introduced around 1972. These included methods to reduce ignition timing along with the use of exhaust gas recirculation (EGR) systems. All of these early systems relied on thermo-vacuum control and simple speed sensing electronics to operate vacuum switching valves to control ignition timing and operate the EGR valve. Unfortunately, the systems did not work very well. Owners complained of vehicle stalling, surging at high speeds, reduced power, and poor fuel mileage. The fuel mileage, which just a few years before very few customers cared about, became the main concern when OPEC nations stopped sending oil to the United States due to support for the Egyptian and Israeli war in October 1973. Gasoline prices almost doubled overnight, and there were gas shortages. Many cities had to enact odd-even rationing for gasoline sales. If it was November 2, your license plate had to end in an even number so you could buy fuel. If your plate ended in an odd number, you had to wait until the next day. As much as the oil crisis served to focus public attention toward fuel use and the related pollution associated, Ford and General Motors were working in earnest to meet

upcoming emissions regulations that would take effect in the 1970s and beyond. Henry Ford II cut Ford’s racing programs in 1970 to use those funds for research on smaller, fuelefficient, and cleaner vehicles. GM’s Ed Cole led his engineering team in the development of the catalytic converter that debuted on many vehicles in 1975. By the late 1970s, small electronic control units (ECUs) were being introduced to control ignition timing and fuel control. The introduction of the oxygen sensor in 1980 was the beginning of feedback fuel control systems, used first by GM. The 1970s and 1980s are referred to as the “malaise era” of vehicles, as performance was scarce and the easiest way to improve fuel economy was to reduce the size and weight of vehicles. This was called downsizing and allowed the switch from V8s to smaller engines—V6 and inline 6- and 4-cylinder engines. The first oil shock in 1973 and the second in 1979 due to the Iranian Revolution and their boycott of selling oil to the United States, along with taking U.S. embassy personnel hostage, doubled the price of gasoline again. Gasoline was around $0.35 per gallon in September 1973 and by fall of 1979 it was $1.20. That may sound cheap today, but incomes were not high. The minimum wage was $2.25 per hour in 1979, and interest rates were over 18%. The advancements in computer technology allowed a renaissance in the 1990s. Carburetors disappeared, replaced with electronic fuel injection and engine control modules (ECMs) that were allowing for more performance, reduced emissions, and good fuel economy. As a reference, a 1975 Ford 7.6-L or Cadillac 8.2-L V8 engine produced barely 250 horsepower. Who could imagine that these same companies were offering engines under 4-L that produce nearly 400 horsepower and achieve very low emissions with very good fuel economy.

Carbon Dioxide and Climate Change While oxygen and CO2 are not pollutants, CO2 levels have been increasing for the past 110 years or so as fossil fuels are used to power electricity-generating stations and motor vehicles. This increase in CO2 levels in the atmosphere traps heat and is one of the contributors to an overall increase in global temperatures. Automakers are working to reduce CO2 levels from internal combustion engines, primarily by focusing on engine and drivetrain efficiency and reducing vehicle weight. The most effective way to reduce all emissions is to reduce the amount of fuel used, so smaller, yet powerful engines are taking the place of the larger engines used in the past. Soon we may be discussing electric motor kilowatt output in hybrid assist or pure electric drivetrains in all types of vehicles, not just from Tesla. TECHNICIAN TIP Diesel vehicles use a particulate filter, and these have been found to be so effective that their use may be applied to gasoline engines in the near future.

Air-Fuel Ratio and Emissions Levels The air-fuel ratio affects emissions output levels and catalyst efficiency. The ideal air-fuel ratio, or stoichiometric ratio of 14.7 parts of air to 1 part of fuel, results in low levels of HC and CO emissions but very high levels of NOx. This air-fuel ratio is also very close to the peak of CO2, which is an indicator of engine efficiency. Notice that CO2 levels drop as the mixture gets richer or leaner, and as the engine is not burning the fuel at peak efficiency (FIGURE 11-5).

FIGURE 11-5 The air-fuel ratio has a direct effect on emissions levels and catalyst efficiency. © Jones & Bartlett Learning.

Description TECHNICIAN TIP The stoichiometric air-fuel ratio of 14.7:1 is considered the most efficient in terms of fuel use, power, and low emissions. However, advancements in fuel delivery with direct gasoline injection, use of air-fuel ratio sensors, variable valve timing (VVT), turbocharging, PCM hardware and software advances, along with overall engine design improvements allow engineers to run very lean mixtures under light load conditions. These mixtures in an older engine would create very high NOx levels. The use of VVT and gasoline direct injection (GDI) allow for a very lean mixture in consideration of the whole combustion chamber

volume, though in reality the dish in the GDI piston is in effect a smaller combustion chamber. Therefore, less fuel is used, resulting in lower overall emissions levels and very high fuel economy. It also reduces CO2 emissions, which is now a goal to reduce the amount of carbon released into the atmosphere.

Rich air-fuel ratios increase HC and CO emissions but are required when increased performance is needed for acceleration or passing situations. Lean air-fuel ratios reduce CO emissions but have higher NOx emissions. Some vehicles use two or more catalysts to deal with HC, CO, and NOx emissions to allow for a wider performance range while still keeping these emissions levels within EPA and California Air Research Board (CARB) limits. Viewing emissions levels on a 5-gas analyzer or reviewing an emissions inspection report provides valuable information for diagnosing what may be the cause of an emissions test failure due to excess emissions in one or more areas (FIGURE 11-6). NOx failures may be caused by the following:

FIGURE 11-6 The 5-gas analyzer assists by displaying the current postcatalyst emissions levels so the technician can determine if a rich or lean mixture, or possible component fault, is the cause for abnormal emissions levels. © Jones & Bartlett Learning.

EGR system fault (if equipped) VVT fault (if VVT is used on the exhaust camshaft to create the internal EGR effect) Fuel system too lean Ignition timing too advanced Modified PCM software Catalyst contamination or failure

An EGR fault usually increases NOx emissions. EGR valves that do not open or EGR passages that are plugged allow increased combustion temperatures and higher NOx emissions. VVT on the exhaust cam is often used to keep the exhaust valve open during the beginning of the intake stroke, allowing exhaust gas to enter the cylinder. This is called the internal EGR effect. VVT faults can impair camshaft timing changes and may be caused by an oil control valve, camshaft position sensor, or VVT actuator. A fuel system that is too lean can cause an increase in NOx emissions. Reduced fuel pressure due to a worn fuel pump, clogged fuel filter, or kinked fuel line may be the cause. Also, air-fuel ratio sensor inaccuracy or clogged fuel injectors (or on older fuel injection vehicles, a fuel rail pressure regulator that is stuck open) can reduce fuel pressure. Many of these faults may also cause a fuel system too lean diagnostic trouble code (DTC). Advanced ignition timing usually increases NOx emissions levels. Ignition timing is not adjustable on most on-board diagnostics second generation (OBD II) vehicles. A fault in the crankshaft position sensor or sensor tone ring/trigger wheel may create ignition timing errors. Modified PCM software to increase power output usually alters the ignition timing and can increase NOx emissions. A contaminated or damaged catalyst will not function to reduce NOx into nitrogen and oxygen. The catalyst is suspect once all other systems are verified to be functioning normally. Very lean conditions will result in cylinder misfire conditions. This will be indicated by very low NOx and CO levels and high HC and oxygen levels since there is little or no fuel combustion during a misfire event. Continued driving with misfires can damage the catalysts. High HC and CO levels with low oxygen and NOx levels indicate a rich mixture fault. This may be caused by high fuel pressure, leaky injectors, use of the wrong fuel injectors, an air-fuel ratio sensor fault, or a contaminated or damaged catalyst. To use the 5-gas analyzer to view emissions levels, follow the steps in SKILL DRILL 11-1. SKILL DRILL 11-1 Using the 5-Gas Analyzer to View Emissions Levels

1. Obtain your assigned vehicle, a scan tool, and use of the 5-gas emissions analyser from your instructor. Install wheel chocks so the vehicle cannot roll forward or backward and apply the parking brake.

2. Position the vehicle so the 5-gas exhaust analyser probe can be inserted into the exhaust system tail pipe(s). (Dual exhaust-equipped vehicles are best analyzed using an analyzer probe in both exhaust outlets.)

3. View the emissions levels on the analyzer with the engine OFF. Most of the emissions levels should be very close to 0 parts per million (ppm) or 0%. Oxygen should be 20% to 21%. This is a quick way to verify that the analyser is intaking ambient air and there is no residual exhaust gas or one or more contaminated filters in the unit. (Analyzers require calibration, usually every few days, to be accurate for emissions testing.)

4. Start the engine and note the readings. A cold engine with cold catalysts will have high levels of HC and CO, and low NOx that slowly begins to lower as the PCM enters closed loop control and the catalysts reach operating temperature.

5. Once the engine is at normal operating temperature, use the scan tool Mode 8 Output state control/Active test to alter injector on-time (this function may be listed under air-fuel ratio test or injector volume test). Increase the injector on-time to create a rich mixture. You should note that HC and CO levels increase and oxygen levels decrease.

6. Decrease the injector on-time. You should note that the HC and CO levels decrease and oxygen levels increase. Also, note that CO2 levels decrease as you change the air-fuel ratio above or below the stoichiometric air-fuel ratio. Repeat altering injector on-time (duration) to view this if necessary.

7. Exit the scan tool Mode 8 testing menu. Perform a short catalytic converter stall test by firmly applying the brakes and placing the vehicle in drive. Press the accelerator to load the engine to the torque converter stall point (usually about 1500–2200 rpm) for a maximum of 20 seconds. Note the emissions readings. NOx should increase due to the very high engine load, and oxygen levels reduce due to NOx creation. After this test, allow the engine and transmission to cool for at least 2 to 3 minutes before repeating.

8. Turn the engine OFF. Create a misfire condition by removing one fuel injector connector or disabling ignition to one cylinder by disconnecting the coil for that cylinder. Start the engine. Note the exhaust readings. Oxygen levels will be much higher than normal due to the misfire (oxygen is not being consumed due to the absence of fuel or spark), and CO2 will be lower than normal. HC may be higher than normal if the fuel was not cut to that cylinder (most PCMs disable the fuel injector for an affected cylinder that has a misfire condition).

9. Review your results with your instructor. This completes this skill drill. Return all equipment and the vehicle to their storage locations. Leave the emissions analyzer on for 10 to 20 minutes so all exhaust gases are purged from the system. © Jones & Bartlett Learning

Emissions Inspection and Maintenance Testing Methods 11-2 Explain emissions inspection and maintenance testing methods.

Vehicle emissions testing methods and requirements vary by geographic location. Very rural areas may not do any vehicle emissions testing, whereas very populous cities may require one or more different types of emissions testing depending on the vehicle type and model year. Emissions testing includes the following: 1. 2. 3. 4.

Two-speed idle test IM 240 dyno test ASM 15/25 dyno test OBD II DLC emissions test

Emissions, or smog, testing usually requires a detailed visual inspection to verify some or all of the following: Verify vehicle identification number (VIN), model year, engine data, emissions data label. Verify that all required emissions equipment is installed as designed. Verify any engine- or emissions-related modifications are legal for the applicable vehicle. Visually inspect for fluid leaks. Perform a visible smoke test. Verify the malfunction indicator lamp (MIL) turns ON, then turns OFF after engine start. A licensed smog inspector will perform the visual inspection and the other parts of the testing. A smog inspector is licensed by the state where the testing is required and performed. The license usually requires attending a smog inspector course, though some are now using web-based (online) courses for this. The applicant must pass the related smog test exam and may also be required to have ASE certifications in A6 (Electrical and Electronics), A8 (Engine Performance), and L1 (Advanced Engine Performance). Some states may have a smog inspector license and a smog inspector and repair license. A smog inspector can only test vehicles and is not certified to repair vehicles that fail a smog test. A technician with a smog inspector and repair license can do both. The smog test begins by verifying the VIN and other vehicle information on the supplied vehicle registration form issued (usually) by the Department of Motor Vehicles (DMV). It is important that all the information matches, especially on older vehicles where you cannot use the bar code scanner to input the vehicle data. TECHNICIAN TIP Although it may not seem like a big deal to verify the VIN, model year, and other data such as engine size, the smog inspector is responsible for verifying that the vehicle on the registration is the one that is in their smog check service lane. Some customers may try to substitute a similar vehicle or they may have made an engine swap. Never take anything for granted; always verify.

Most smog techs use an emissions test form to note all the vehicle information (FIGURE 11-7). This form usually has a checklist similar to what the smog tech will input on the smog test machine for the related emissions equipment that could be on a vehicle.

FIGURE 11-7 Most smog technicians use a form to check off items or make notes as they perform the visual inspection. © Comzeal images/Shutterstock.

The underhood emissions label lists which systems the vehicle should have (FIGURE 11-8). This label provides the vehicle model year (MY), emissions certification level (CA or EPA, or both), EVAP type, engine size, and the emissions equipment on the vehicle. The sample shown in Figure 11-8 is for a 2020 MY Ford vehicle EPA and California standards. It has 2.5 liter engine equipped with a three-way catalyst (TWC), heated air-fuel ratio sensor (HO2S/WR), heated oxygen sensor (HO2S), exhaust gas recirculation and evaporative emission control (EVAP).

FIGURE 11-8 The underhood emissions label shows the vehicle model year, emissions application, and what emissions control devices are installed. © Jones & Bartlett Learning.

The smog inspector will verify this equipment is on the vehicle and check off the applicable boxes on the form. The inspector will note if any equipment is missing or modified. Missing equipment will usually result in a vehicle failing the smog test visual inspection. Modified can apply to replacing an original equipment item with an aftermarket replacement. A common example is the installation of a cold air intake in place of the original unit. Smog-compliant aftermarket components will have a CARB executive order (EO) number (FIGURE 11-9).

FIGURE 11-9 Aftermarket components may require an EO number showing they are certified for use on emissions-controlled vehicles. © Jones & Bartlett Learning.

The smog inspector can verify whether a component is approved by visiting the related website to determine if it has an EO number. Note that some states may allow certain aftermarket parts without an EO number. This is why smog technicians are licensed—the process of going through the related coursework trains them for what is required to correctly perform a smog inspection in their area. The tech will check for any fluid leaks that would present a danger to running the vehicle during the smog test (FIGURE 11-10). Large oil, coolant, transmission, or fuel leaks are all reasons to abort the inspection and recommend those be repaired first. You do not want to risk damage to the test equipment or vehicle during the test procedure.

FIGURE 11-10 Check for leaks as part of the smog inspection. A large leak could lead to engine or test equipment damage during the inspection.

The smog inspector may need to perform a visible smoke test at the exhaust before the emissions sniffer probe is installed (FIGURE 11-11). The exhaust should essentially be invisible during this test. Dark blue smoke indicates engine oil burning, and dark black smoke indicates a very rich fuel condition. Large amounts of white smoke can indicate coolant is getting into the cylinders. Follow your state guidelines to review the results of this test if required and when to pass or fail this portion of the test.

FIGURE 11-11 A visible smoke test is performed to see if large amounts of particulates are present. © Ody_Stocker/Shutterstock.

At the appropriate time during the test, verify the MIL turns on when the ignition is turned ON and that the MIL turns OFF after engine start (FIGURE 11-12). Follow test procedure guidelines for your state if the MIL does not turn ON at all or does not turn OFF after engine start.

FIGURE 11-12 The smog inspection usually requires verifying MIL operation. © Jones & Bartlett Learning.

Two-Speed Idle Test The two-speed idle test has been used for many years. The limitation of this test is that it is unable to measure NOx because there is almost no engine load during the test. This test focuses on HC and CO emissions and usually uses only a 4-gas analyzer. It is usually performed in areas that exceed federal pollution standards—but not by much. It may also be performed on antique vehicles if they are required to be inspected. TECHNICIAN TIP Some vehicles in areas where a dyno test is usually performed can only be tested using a two-speed idle test. These include all-wheel drive, full-time four-wheel drive, and some hybrid vehicles.

The two-speed idle test is done by connecting an rpm pickup sensor, either on a spark plug wire or the type that can detect rpm without an ignition connection, and inserting the gas analyzer sniffer probe into the tailpipe. The 2500 rpm test is usually done first, then the idle test. This is done to ensure the engine and catalyst are at normal operating temperature. Note that this, like all the tests, includes the visual inspection items (FIGURE 11-13).

FIGURE 11-13 The two-speed idle test operates the engine at idle and at 2500 rpm during the tailpipe emissions measurement portion of the test. © Jones & Bartlett Learning.

IM 240 Emissions Test The Inspection and Maintenance (IM) 240 test is designed to mimic the EPA’s Federal Test Procedure (FTP). The test takes 240 seconds, or 4 minutes, of dyno time (FIGURE 11-14). A great deal of research went into this test with respect to the smog tech being able to follow the drive pattern to successfully complete the test. Although 4 minutes is not a long time, it can seem like a long time on the dyno, especially when the smog tech must follow the speed trace as the test proceeds. The difficulty lies in the different ways various vehicles react to accelerator input and braking. Yes, braking. During this test, you must rapidly decelerate from about 35 mph to 0, and then continue the rest of the test. The test aborts if the smog technician is unable to follow the trace, requiring the tech to try again.

FIGURE 11-14 The most common IM 240 drive cycle is shown. The test takes 4 minutes of dyno time to complete. © Jones & Bartlett Learning.

It takes a great deal of practice to do this drive cycle in a variety of vehicles. The advantages of this test are that it does test for all three pollutants—HC, CO and NOx—and does so by mirroring the FTP’s test. This test usually requires connection of the emissions analyzer to the OBD II connector for applicable vehicles, use of the exhaust sniffer pipe, and use of an rpm detection device when the OBD II connector is not available. The smog tech must also secure the vehicle for the dyno portion of the test. The dyno places a load on the driveline to simulate the vehicle driving under the actual conditions. Most dynos have a built-in scale to measure the weight over the axle that will be on the dyno rollers. The analyzer uses the measured weight to adjust load and also to verify that the vehicle is within weight specifications for the type that was entered into it. This is done to ensure accurate test results and to make substituting a vehicle for the one that should be tested more difficult. Once the vehicle weight is taken, the vehicle is placed on the rollers. The vehicle must then be secured for the dyno test. It is recommended that all vehicles be strapped by the frame to the tie-down eyelets to keep the vehicle from moving off the dyno rollers during the test. This is because the front wheels can also steer, and if the steering wheel is turned during the test, either by the smog tech or any other reason, the

vehicle can lurch forward off the dyno (FIGURE 11-15). This could cause a great deal of damage, injury, or even death. Strap the vehicle down using appropriate tie-downs connected to the vehicle subframe and to the tie-down eyelets provided on the dyno. Once the vehicle is secured, the smog tech can then proceed with the test. Note that if the temperature is above 70o F, most areas require the use of an approved fan to force air through the radiator during the test.

FIGURE 11-15 All vehicles must be strapped down during emissions dyno testing. © Jones & Bartlett Learning.

ASM 15/25 IM Testing The ASM 15/25 test was created to simulate the IM 240 test but in a much simpler format for the smog tech operating the vehicle on the dyno. Rather than operating the vehicle over a wide range of speeds, in acceleration and deceleration conditions, the smog tech brings the vehicle to 15 mph and then when indicated accelerates to 25 mph. This is much easier for the tech, although it still requires practice to get it right. The low-speed 15-mph portion of the test has the vehicle under heavy load with the goal of measuring NOx emissions. The second portion of the test is at lower load and is focused on measuring HC and CO. The vehicle is placed on the dyno as described for the IM 240 test. The OBD II connector is connected on applicable vehicles and, if needed, an engine rpm sensor is used. The engine rpm is critical in that the driver is not to shift gears during the test for automatic vehicles. Manual transmission vehicles require the smog tech to shift to the appropriate gear, usually second for the 15-mph portion and third for the 25-mph portion. To perform a dyno-based emissions test inspection, follow the steps in SKILL DRILL 11-2. SKILL DRILL 11-2 Performing Dyno-Based Emissions Test Inspection

1. Obtain a vehicle and a related emissions test inspection form if one is used in your shop.

2. Check the vehicle for any large oil, fuel, or coolant leaks. Do not test a vehicle that has any of these conditions. They must be corrected before the vehicle can safely be used on the emissions dyno.

3. Drive the vehicle onto the dyno. Front-wheel-drive (FWD) vehicles will need to use come-along tie-down straps to secure the vehicle so it does not try to drive off the dyno during the test. Also, use wheel chocks at the rear wheels and apply the parking brake. Rear-wheel-drive (RWD) vehicles have the front wheels chocked and are tied down to the dyno at the rear of the vehicle. You must chock the front wheels as well to ensure the vehicle does not come off the dyno during the test. Leave the engine ON and turn traction control systems OFF for the test.

4. Begin the emissions inspection. Review the underhood label and the emissions handbook to verify what emissions components should be installed on the vehicle. Verify that each item is there—EGR valve and catalyst, for example. If they are missing or modified, note that on the inspection form.

5. Perform any functional tests if required. This may include testing an EGR valve using a handheld vacuum pump or checking ignition timing on an older vehicle.

6. Input the data into the emissions analyser. Your inspection form helps you along with this. Many states want you to use bar code scanners for the VIN. This helps eliminate cheating, where one vehicle runs the dyno test but the VIN and other data are for a different vehicle. Note that this type of cheating can result in fines or a felony conviction for emissions test fraud in many areas. Complete each portion of the input to continue to the next step.

7. Connect the OBD II cable from the analyser to the vehicle (for 1996 and newer vehicles). Older vehicles may require an rpm sensor be used to monitor engine rpm during the test. You may need to use an electric fan placed in front of the vehicle during the test if the temperature is above approximately 70º F. Insert the exhaust probe into the vehicle exhaust tailpipe. Dual exhaust vehicles require a probe for each side of the exhaust. Use the dual exhaust adapter and second probe if required.

8. Set the emissions analyzer screen to the dyno portion of the test. Position yourself in the driver’s seat, then place the vehicle in drive (or in a manual transmission, first gear). When prompted by the analyser, accelerate to the designated speed. For manual transmissions, this usually requires a shift to second or third gear. Leave automatic transmissions in drive. Note that if engine rpm is too high or too low, the analyzer will abort the test.

12. Test the fuel cap for leaks if required. This requires removing the fuel cap and installing it, with an adapter if needed, onto the cap test device on the analyzer. The analyzer will then test the cap by placing a small amount of pressure on it. Remove the cap and reinstall on the vehicle after the test is complete.

13. The analyzer will complete the test and then prompt you to drive the vehicle off the dyno while the test results print out. Some analyzers will display test results on the monitor, others only on the official printout.

14. Remove wheel chocks and any tie-downs. Disconnect the OBD II cable and any other devices connected to the vehicle during the test. Carefully store them on the analyzer’s storage system to prevent damaging them.

15. Carefully drive the vehicle off the dyno. Complete any paperwork and the repair order. Attach the emissions results printout to the RO and emissions test form. This completes this skill drill. © Jones & Bartlett Learning

Emissions Handbook Every smog tech should have a resource to quickly look up how to test ignition timing, EGR, and EVAP systems. These items often must be checked on 1995 and earlier vehicles that do not have OBD II as part of a smog inspection. Also, these resources have charts for every vehicle made, showing what emissions equipment should be on the vehicle based on engine, California or federal, and other possible variations. This is a great help to verify that the underhood label is correct or if it is missing.

Emissions System Standards California has the most severe air pollution problems due the number of vehicles in use and geography that is conducive to trapping the pollutants in the populated areas. The EPA was established in 1970 under President Nixon to deal with polluted air and water. Water in the Great Lakes was unfit to swim in, unregulated chemical dumping was turning lakes and rivers into contaminated drinking water, and air pollution was causing smog alerts in many California cities. When CARB was created under Governor Ronald Reagan to deal with the air pollution issue, California began to establish standards that were stricter than the EPA, since California’s air problems were bigger than those in most other areas in the United States. Other states have adopted California’s emissions standards in an effort to reduce pollution. Technicians once referred to EPA standard vehicles as 49-state vehicles, but that is no longer

the case. The underhood emissions label shows the EPA and California emissions standards that the vehicle meets (FIGURE 11-16).

FIGURE 11-16 The underhood emissions label includes the EPA and California emissions standards that the vehicle conforms to. © Jones & Bartlett Learning.

Note that a vehicle that does not meet the California standard will state that on this label (FIGURE 1117). These vehicles cannot be sold new by a dealer in California or other states that have adopted the CARB emissions standards. They can, however, be brought into these states as used vehicles, for example if a person moves to California from another location.

FIGURE 11-17 New vehicles that are not assembled with California emissions components or related PCM software cannot be sold new in California or in other states that have adopted the California standards. © Jones & Bartlett Learning.

The EPA uses alphanumeric designations for their emissions standards. CARB uses abbreviations as shown in TABLE 11-1. Tier 1 and TLEV vehicles were common on early OBD II vehicles; however, these designations were not used after MY2003. The other designations continue to be used; however, the standards change for applicable model years. Some of the designations are based on how long the vehicle will be under a factory emissions warranty. What this means is that the manufacturer is stating that its ULEV, or SULEV, will still meet emissions standards at 150,000 miles or 15 years. If a system or component fails, then that affects emissions levels, and it will be under warranty during that time period or mileage limit. Zero-emissions vehicles are currently either hydrogen fuel cell or full electric. TABLE 11-1 CARB Abbreviations Tier 1

No longer used after MY2003

TLEV

Transitional Low Emissions Vehicle (no longer used after MY2003)

LEV

Low Emissions Vehicle

ULEV

Ultra Low Emissions Vehicle

SULEV

Super Ultra Low Emissions Vehicle

ZEV

Zero Emissions Vehicle

Much of this is also a chess game for manufacturers. Tesla sells only electric vehicles. This earns them emissions credits that they can sell to other manufacturers. For example, Fiat Chrysler Automotive (FCA) and General Motors (GM) have purchased over $2 billion in ZEV credits for use in their U.S. and European operations. This also affects other automakers. For example, car companies may want to sell more high-performance vehicles or full-size trucks, but to meet their overall emissions standards, they would need to offset those vehicles that pollute more by selling more ULEVS and SULEVS or ZEVs (if they manufacture any). All regulations are subject to change due to technology taking longer to achieve the desired standard, a breakthrough that allows a standard to be met earlier, or policy change based on current leadership at the federal and state levels. As technicians, it is our job to ensure vehicles are maintained and repaired so they continue to meet the standards they were designed for.

Emissions System Diagnosis 11-3 List possible causes of a failed onsite emissions test.

Vehicles can fail an emissions test for the following reasons: Missing or modified emissions-related components MIL is ON Too many incomplete monitors Emissions levels are excessive A system failed its functional test A combination of these A visual inspection where the smog tech notes a modified component without an EO number or where there is a missing component will require that the modification be undone and restored to original specifications or an approved component be used. A MIL ON condition requires that the related DTC diagnostics be followed. Too many monitors incomplete will require the customer to drive the vehicle for a few days and then bring it back. If the customer is erasing DTCs, then the monitors will reset to incomplete and the vehicle will fail again. Ask the customer whether anyone erased DTCs recently to turn off the MIL, or if a recent MIL ON repair was made. Do not assume the customer did this, but be sure to discuss it to prevent this type of comeback. Excess emissions level diagnosis where no DTC has set requires using the smog test results to narrow your diagnostic focus as follows: Excessive HC, CO, and NOx normal or below normal, oxygen above normal Misfire Partially clogged injector Lean condition Low fuel pressure Vacuum leak Unmetered air Faulty MAP or MAF Engine mechanical issue Faulty HO2S or A/F sensor Failing catalyst Excessive HC and CO; NOx, CO2, and oxygen below normal Rich mixture High fuel pressure Faulty HO2S or AF sensor Exhaust manifold leak Faulty secondary air system Faulty catalyst Excessive NOx EGR fault (if equipped) Plugged passages EGR valve stuck closed EGR valve cannot open fully EGR-related component fault VVT Fault Faulty VVT actuator

Faulty VVT control valve Timing chain installed incorrectly Cooling system fault Incorrect thermostat Low coolant level Cooling fans or clutch fan fault Faulty catalyst These listed items require application of the diagnostic process based on the service manual information for each. Testing of these systems has been covered in MAST: Automotive Engine Performance, which serves as an additional reference, and this text. Your understanding of the chemistry of combustion as presented in MAST: Automotive Engine Performance is not something you can just learn and then forget about. Here is the real-world application for using that simplified formula. For example, if HC and CO are elevated but oxygen is at a normal or higher level compared to other vehicles you have tested, would you look at rich condition or the catalyst? A rich condition would use up most of the oxygen, if not all of it during the combustion process, right? Yet this vehicle has oxygen in the exhaust. This could indicate an exhaust leak ahead of the HO2S or AF sensor, or it could indicate a faulty catalyst. The ability to use your engine performance knowledge is what is going to enable you to diagnose smog inspection emissions level failures. Systems that fail a functional test require following the related diagnostics for that system (FIGURE 11-18). Use the service information as your guide and any additional information from your engine performance textbooks and related course notes. A combination of failures requires you take care of them, usually in this order:

FIGURE 11-18 An emissions failure requires a focused diagnostic process to successfully isolate the cause. © Jones & Bartlett Learning.

Description 1. 2. 3. 4.

Modified or missing components DTC diagnosis Completion of all monitors Repair systems that fail functional tests

Once these are complete, drive the vehicle to verify the MIL is OFF and the monitor tests have completed and passed. If all is okay, check emissions levels (most dyno-based tests allow you to do a pre-check test); if okay, do the actual emissions test. If emissions levels are still high, continue diagnoses based on the current emissions level readings.

Case Study: Emissions System Failure A customer has brought their car in for emissions test failure diagnosis. It was tested at a “Test Only” station, as many vehicles with high emissions levels and test failure rates are often required to be tested at test-only stations. The reason is that vehicles with high emissions level profiles can be a prime target

for false failures or forced failures if a test station has an interest in also making money from the related suggested repairs in order to pass. The vehicle has very clean HC and CO levels; however, NOx failed at the 15-mph heavy load test and is higher than average at the 25-mph test portion (FIGURE 11-19). The technician does a thorough visual inspection to verify all emissions components are present, there is no tampering, and the catalysts are present and, if replaced, have the correct EO/CARB part number. The catalysts have not been replaced.

FIGURE 11-19 A 1996 Toyota Camry failed emissions for high levels of NOx. © Jones & Bartlett Learning.

Description The 5S-FE engine in this vehicle uses an EGR system to help control NOx along with two 3-way catalysts. The technician connects the vehicle to the emissions analyzer to verify current emissions levels. Since NOx is the focus, the technician performs a torque converter stall test to load the engine and create NOx. The NOx levels are much higher than normal and verify that the condition is current and not intermittent. The technician begins by verifying EGR valve operation. This EGR system uses a back-pressure transducer and an EGR vacuum switching valve. The technician starts the engine and uses a handheld vacuum pump to operate and open the EGR valve. The engine stalls when the technician applies vacuum to the valve. This indicates that the valve and related EGR ports are okay, as the EGR gas was able to enter the engine at idle and dilute the mixture to the point the engine stalled. The technician refers to the service information for EGR system inspection (FIGURE 11-20). Even though a DTC has not stored, the DTC diagnostics for the EGR system provide a thorough step-by-step process for verifying system component operation. The technician applies vacuum to the EGR vacuum solenoid (VSV) and then commands the VSV ON with the scan tool Mode 8 output state/active test. The vacuum drops, indicating the VSV is okay. The technician then continues component testing, moving to the EGR transducer (modulator) valve (FIGURE 11-21).

FIGURE 11-20 Service information provides emissions system operation and test procedures. © Jones & Bartlett Learning.

Description

FIGURE 11-21 The service information provides details on component tests, such as the EGR vacuum modulator for this vehicle. © Jones & Bartlett Learning.

Description The technician performs the vacuum modulator test. The modulator passes the first test. but at 2500 rpm there is no resistance to air flow, failing that test. The technician replaces the modulator. The technician performs a stall test again while watching emissions analyzer NOx levels and they are now at 83 ppm during this test. This indicates the EGR system is now working normally again. The technician performs the EGR OBD II drive cycle to ensure the monitor is complete and the results are okay. The technician completes the RO and attaches printouts of the emissions readings to support before and after emissions levels. The customer will have to take their vehicle back to the test-only station for another test, but it should pass now. This completes this emissions repair.

WRAP-UP Ready for Review Vehicle emissions standards are to limit the amount of unmonitored pollutants released into the atmosphere. The major greenhouse gases that an internal combustion engine creates are oxides of nitrogen, hydrocarbons, particulate matter, carbon monoxide, and carbon dioxide. Incomplete combustion can be caused by an engine misfire, poor fuel quality, or a mechanical problem with the engine. There are three major emissions testing standards: two-speed idle test, IM 240 test, and ASM 15/25 IM testing. Emissions testing is used to verify the engine is operating at the standards at which it was designed to operate in relation to the model year of the vehicle. The emissions handbook will give the specifications of the vehicles produced in each model year. The MIL will give the technician the ability to diagnosis accurately and quickly the failed component within the system.

Key Terms 5-gas analyzer A tool that uses sensors to measure the level of gases in the exhaust stream. ASM 15/25 dyno test Acceleration Simulation Model dyno-type emissions test. Usually a shorter and easier to perform dyno-based emissions drive pattern with the vehicle operated at 15 mph under heavy load and 25 mph at light load. California Air Research Board (CARB) The state organization charged with protecting the public from the harmful effects of air pollution and developing programs and actions to fight climate change. Carbon dioxide (CO2) A colorless, odorless gas that exists naturally in the air, it also results from burning a hydrocarbon fuel, contributing to global warming. Carbon monoxide (CO) A colorless, odorless gas that is highly toxic and causes asphyxiation when inhaled. It is produced through incomplete fuel burning, such as with vehicle emissions. Environmental Protection Agency (EPA) A U.S. federal government agency that deals with issues related to environmental safety. Hydrocarbons (HC) Microscopic unburned fuel particles that contribute to photochemical smog and help form ground-level ozone. IM 240 dyno test A very thorough drive cycle test for the Inspection and Maintenance (smog) emissions system test. This test mirrors the EPA Federal Test Procedure (FTP) test drive cycle. OBD II DLC emissions test Later OBD II vehicles may be eligible for this test, in which the emissions analyzer connects to the DLC and reviews OBD II monitor test results to determine if the vehicle passes or fails. This test still requires a visual inspection and smoke test. Oxides of nitrogen (NOx) A vehicle emission that contributes to ground-level ozone, they are produced when nitrogen and oxygen react during combustion, given sufficient temperatures and pressures. Forms include nitrogen oxide and nitrogen dioxide. Oxygen (O2) A colorless, odorless reactive gas, the chemical element of atomic number 8 and the lifesupporting component of the air. Two-speed idle test A nondynamometer-type emissions test, performed at 2500 rpm and engine idle speed to measure exhaust emissions.

Review Questions 1. A vehicle has failed a loaded mode dyno-type emissions test for excess NOx emissions levels. Which of the following could be the cause of the failure? a. Electric EGR valve duty cycle ON percent is too high. b. No carbon is present in the EGR passages. c. The EGR pressure transducer diaphragm damaged. d. Tires of incorrect size were installed, causing an increased load on the engine. 2. The vehicle report on the next page shows that this vehicle failed a two-speed idle emissions test. Which of the following could cause this failure? a. EGR valve stuck closed b. Lazy oxygen sensor c. Low fuel pressure d. Misfire in cylinder 1

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Description 3. The customer is upset that their vehicle failed the emissions test. Why did this vehicle fail the emissions test based on the results shown below? a. Failed A/F sensor b. Failed HO2S c. Gas cap seal failed d. Monitors incomplete

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Description 4. This vehicle failed an emissions test (results on the next page) for all of the following reasons EXCEPT: a. a faulty catalyst. b. MIL ON. c. excess CO2. d. excess NOx.

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Description 5. A misfire during loaded mode emissions testing may be indicated by which of the following on a preOBD II vehicle? a. Excess CO2 emissions b. Excess NOx emissions c. A stuck closed EGR valve d. Excess oxygen levels 6. Pre-OBD II vehicles may require all of the following during some state/municipal emissions tests EXCEPT: a. an ignition timing inspection. b. an EVAP leak check. c. a monitor status check d. a gas cap leak check. 7. Most of the following can cause excess HC levels EXCEPT: a. a faulty oxygen or A/F sensor. b. an ignition misfire. c. resistance in the ECT sensor circuit. d. a cylinder 3 fuel injector open circuit. 8. Most of the following are required tools for the smog inspector’s toolbox EXCEPT: a. a portable 5-gas analyser. b. a handheld vacuum pump.

c. a timing light. d. locking hose pinch pliers. 9. The vehicle test report shown below indicates which of the following? a. MIL is ON failure. b. Emissions components modified. c. NOx emissions levels too high. d. Air cleaner type is incorrect.

© Jones & Bartlett Learning.

Description 10. Clean piping refers to which of the following? a. Running the vehicle under load to clear carbon out of the engine and exhaust system b. Cleaning the gas analyzer sniffer probe c. Substituting a vehicle for the one that should be tested d. Performing a hard reset on the gas analyzer and performing gas bench calibrations

ASE Technician A/Technician B Style Questions 1. Refer to the smog check report shown below. Technician A says diagnosing the cause of this failure may be easier after reviewing the OBD II EGR Mode 6 test results. Technician B says a faulty oxygen sensor could cause this test result. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B

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Description 2. Refer to the smog inspection report shown below. Technician A says clogged EGR ports could cause this test result. Technician B says that a faulty catalyst could cause this test result. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B

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Description 3. Refer to the smog inspection report shown below. Technician A says that a slow-reacting oxygen sensor could cause this test result. Technician B says installation of an unapproved aftermarket catalyst could cause this test result. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B

© Jones & Bartlett Learning.

Description 4. Refer to the two-speed idle test results shown below. Technician A says the vehicle is running lean. Technician B says the catalyst may have reached a higher temperature for the second fast idle test. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B

© Jones & Bartlett Learning.

Description Description 5. Refer to the emissions label shown below. Technician A says this vehicle does not have an EVAP system. Technician B says that this vehicle uses VVT for EGR. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B

d. Neither Technician A nor Technician B

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6. Refer to the emissions label shown below. Technician A says this vehicle uses a secondary air system. Technician B says this vehicle meets U.S. and California emissions regulations. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B

7. Technician A says a missing emissions label requires that you fail the vehicle since it is impossible to determine the emissions equipment that should be present. Technician B says an aftermarket air intake and air cleaner always result in a failed emissions test visual inspection. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B 8. Technician A says all-wheel-drive vehicles require use of the two-speed idle test instead of a dynotype test. Technician B says erasing DTCs to turn OFF the MIL will allow an OBD II vehicle to then pass an emissions test, where emissions levels are below threshold limits. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B 9. Technician A says a gasoline vehicle with visible blue or black smoke after the applicable test procedure can still pass if the emissions levels are below threshold limits. Technician B says nonOBD II vehicles require performing an EVAP pressure test for system leaks. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B 10. Refer to the underhood emissions label shown below. Technician A inspects ignition timing and notes it is 13o BTDC and fails the timing test results for the functional test. Technician B says this vehicle

requires an EVAP leak test as part of the emissions inspection. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B

© Jones & Bartlett Learning.

© Jones & Bartlett Learning.

CHAPTER 12

Engine Noise, Vibration, and Harshness Diagnosis LEARNING OBJECTIVES After studying this chapter, you should be able to: 12-1 Describe noise, vibration, and harshness concerns and applicable diagnostic tools. 12-2 Isolate the cause of top-end engine noise. 12-3 Isolate motor mount failures. 12-4 Determine the cause of engine detonation and preignition. 12-5 Interpret engine fluid issues affecting engine performance. 12-6 Analyze the integrity of the cylinder head gasket.

YOU ARE THE AUTOMOTIVE TECHNICIAN A vehicle has come in with an engine noise that is more apparent when the engine gets up to operating temperature. Once the engine reaches operating temperature, the valve cover has a metallic noise coming from it. What should the technician do first? Determine whether the noise is from the timing chain because of wear. Check the oil and top it off if it is low. Remove the valve cover because the noise is coming from this location.

Introduction Noise, vibration, and harshness (NVH) issues have existed since vehicles were first manufactured. Many early vehicles had the engine bolted to the vehicle frame, which may have been wood or cast iron with little more than a piece of leather to help isolate vibrations. Customers were not concerned with the noise and vibrations. That was how the vehicles were at the time, so no one knew that NVH causes could be isolated or eliminated. It was not until the 1930s that engine mounts were used, along with suspension bushings and rubber body mounts to isolate NVH. Today’s vehicles are much more sophisticated, using balance shafts in engines, active engine mounts, and even the vehicle sound system to dampen or eliminate NVH. Hybrid and electric vehicles are so quiet in EV mode that other noise (e.g., tire tread) must now be a major consideration during vehicle design. The use of aluminum and carbon fiber helps save weight but also creates new NVH issues that must be corrected. Technicians become involved when a component fails, such as an engine mount, and it must be diagnosed and repaired.

Diagnosing Engine Noises 12-1 Describe noise, vibration, and harshness concerns and applicable diagnostic tools.

The ability to pinpoint engine noises improves with the use of special tools and techniques. Try listening for noises at different locations on the engine. Use an automotive stethoscope, electronic chassis ear, mini electric engine ear, or a long piece of fuel or heater hose to locate the leak. An automotive stethoscope uses a long, solid metal probe that when held against a solid component transfers the sound to the earpieces. If a suspected noise is underneath a cover, place the stethoscope against a nearby bolt or solid component, enhancing noise transmission. Noise transfer is more discernable through a solid object rather than covers made of metal, plastic, or composite material. For example, an engine with a suspected timing chain slap is better isolated to your ear when placing the stethoscope tip against a front cover bolt or against the block to cover the mating surface, rather than on the middle of the cover. This technique holds true when searching for any vehicle noise using a stethoscope. If a stethoscope is not available, substitute a long screwdriver or extension in its place. When using any of these tools around a running engine, observe caution (FIGURE 12-1). Place the end of the tool just forward of your ear, against your skull. Avoid letting the tool near your inner ear because its vibrating components may cause damage.

FIGURE 12-1 These listening tools will allow the technician to pinpoint the source of the noise, which the tech can use to diagnose what is causing it.

© Jones & Bartlett Learning.

To locate air pressure noises, such as vacuum or exhaust leaks, modify the stethoscope. The metal rod of a stethoscope is often removable. With the metal rod removed, the transfer tube connects to the earpieces on one end and is open on the other. Place the open end of the tube where the leak is located. If the transfer tube is too short to reach the intended location, remove the transfer tube and install a piece of vacuum tubing cut to the desired length. Attach the vacuum tubing to the stethoscope and continue testing. SAFETY TIP Use caution when using any tool, such as a stethoscope, around moving engine parts to prevent personal injury. An electronic engine ear, or chassis ear, powered by an internal battery, uses an ultrasensitive microphone providing a full range of sound. Mounted on a flexible shaft, a sensor tip allows access to hard-to-reach areas. To help pinpoint noise and vibrations, the tool includes an inductive metal probe that can be used similarly to a stethoscope. Some tools include a long cable (some up to 16 feet) and a metal clamp to secure the probe during a test drive. A version of the tool is available with wireless transmitters and is much easier to connect the microphones for use. A volume control allows the user to adjust sound level heard through headphones or earbud style earphones easily, overcoming shop noise. The wireless version uses a receiver that amplifies the signal and plays it through a speaker. A wire tachometer is an inexpensive tool that can be used to determine the rpm at which a noise or vibration is occurring. Have an assistant operate the engine at a slowly increasing rpm until the concern occurs, or if it occurs at most times, focus on where it is at its most extreme. Extend the tachometer wire by turning the top of the tool clockwise and note the vibration of the wire. Extend and retract the wire to locate the spot where the wire vibrates with the greatest frequency. Once you have the wire tachometer set to the maximum wire vibration, you can then read the rpm indicator on the tool. This indicates the rpm at which the noise and vibration are greatest and can help you isolate the cause to a first- or secondorder vibration. A first-order noise would have an rpm reading that matches the engine rpm. This indicates it is happening once every crankshaft revolution. A second-order vibration would occur at every other crankshaft revolution and could indicate a camshaft or valve train–related fault. A half-order vibration would occur twice per crankshaft revolution. Using this tool can quickly assist you in isolating the rpm range where the noise or vibration occurs so you can quickly focus your diagnosis to the engine crankshaft–related components or valve train components. It can also eliminate those and focus on causes that can create noises at uneven intervals, such as a damaged flexplate or front engine accessory drive component. To practice using various NVH diagnostic tools, follow the steps in SKILL DRILL 12-1. SKILL DRILL 12-1 Using NVH Diagnostic Tools: Automotive Stethoscope, Chassis Ear, and Wire Tachometer 1. Obtain your assigned vehicle and a technician’s stethoscope. 2. Clean the stethoscope ears with an alcohol swab or with rubbing alcohol on a cotton ball or a small, clean towel. This will ensure they are clean for use in your ears. 3. Start the engine on your vehicle and use the stethoscope to listen at the following locations: a. Alternator pulley bearing: Normal is a whirring noise; bad is a grinding sound. b. Rocker/cam cover near the timing chains or cylinder 1 if overhead valve (OHV) and not overhead cam (OHC): Normal is light noise from cam to lifter/rocker action and timing chain noise; bad may include tapping from a collapsed lifter or

misadjusted rocker clearance and timing chain slap due to worn timing chain guides. c. The EVAP purge valve solenoid: Normal is a ticking sound from duty cycle activation of the solenoid; bad may be no noise or a buzzing without any ticking. 4. This completes the technician’s stethoscope section of the Skill Drill. Shut the engine OFF. Clean the stethoscope ear buds with an alcohol swab or cotton ball and return them to their storage location. 5. Obtain the chassis ear toolkit from your instructor. Note that there are variations of the chassis ear tool. This Skill Drill is based on the most common type, which uses wireless microphone transmitters and a receiver unit. There are units that use wired transmitters, and some units can connect to a digital storage oscilloscope (DSO) so you can view the sound waves on the scope display. 6. With the engine OFF, install the chassis ear transmitters to the alternator housing one to the top of the rocker cover and one to the radiator support. 7. Start the engine. Use the chassis ear receiver to listen to the sound from each transmitter. The sound from each location should be similar to what you heard with the stethoscope. Note that the sound from the microphone attached to the radiator support should be almost inaudible since there should not be any sound emanating from it. The chassis ear is an excellent tool to isolate the source of a noise issue. 8. Shut the engine OFF. Remove the chassis ear transmitters and return them to the chassis ear storage box. Turn OFF the chassis ear receiver if necessary. Return the chassis ear to its storage location. 9. Obtain a wire tachometer and a 1-ounce stick-on wheel weight. With the engine OFF, clean a small area of the crankshaft pulley and then attach the 1-ounce weight to the pulley at the flat part of the outer edge. Note that you may need instructor assistance to locate where to install the stick-on weight. Once it is installed, start the engine to verify that the weight remains in place. When okay, move on to the next step. 10. With the engine running you may feel a slight vibration. If not, slowly increase engine speed until you feel the vibration. Once you feel the vibration, use the wire tachometer. Place the tachometer on a flat surface, such as the top of the instrument panel. Measure the vibration by extending the wire out of the housing until the wire is vibrating in sync with the vibration you feel. You may have to extend and retract the wire slowly to note the point at which the wire vibrates with the greatest movement. 11. Once you have adjusted the wire so it is vibrating at its greatest movement, note the rpm reading indicated on the tachometer housing. This reading should be very close to the engine rpm when you did the measurement. This indicates a first-order vibration, as the vibration occurs with every crankshaft revolution. If we were able to install the weight on a camshaft sprocket, it would be at every other crankshaft revolution and would indicate a second-order vibration. The wire tachometer is a very simple, but effective, device to isolate the rpm at which a vibration is occurring. From this, you can then focus on which components are rotating at that speed in relation to engine rpm. 12. Turn the engine OFF. Remove the stick-on weight from the crankshaft pulley. Return the wire tachometer to its storage location. Review your findings with your instructor to conclude this Skill Drill. © Jones & Bartlett Learning

TECHNICIAN TIP

Some DSO manufacturers, such as Pico Scope, offer an NVH accessory kit. This allows the technician to view the waveform of a noise using a microphone that sends a signal to the DSO (FIGURE 12-2). This often requires inputting some information into the DSO, including crankshaft pulley diameter and the diameter of the pulley of the component you suspect has the noise, such as an alternator pulley. This allows you to see the rpm of the alternator when the noise occurs at its greatest amplitude.

FIGURE 12-2 A digital storage oscilloscope can be equipped with a microphone to then display the sound waveform for NVH diagnosis. © Jones & Bartlett Learning.

Determining the Noise Location After determining that the engine noise is abnormal, the next step is determining the location and cause of the particular sound. The art of engine noise diagnostics is eliminating all the possibilities that could cause the noise down to one. This step is critical to proper diagnosis and involves the use of the stethoscope, engine or chassis ear, or a solid metal tool. When using these tools, remember the sound is always the loudest when the tool is closest to the source of the noise. Common noise locations include the following: 1. 2. 3. 4. 5.

Fuel injector(s) Top end of engine Bottom end of engine Front of engine Rear of engine

Fuel Injector Noise Fuel injectors are a common source of an engine ticking noise complaint, which is often a result of normal operation. Fuel injectors are electronic solenoids that rapidly open and close during operation, making a ticking noise. Gasoline direct injection (GDI) fuel injectors are by nature much louder than a standard fuel-injected engine (FIGURE 12-3). The increase in operating noise levels is a combination of the piezoelectric injectors and the camshaft-driven high-pressure fuel pump control solenoid located on the body of the fuel pump. Due to the extremely high fuel pressure, the solenoids that control fuel pressure by turning ON and OFF, both at the high pressure fuel pump and at injectors, must be much stronger and consequently noisier. Also, when turning high pressure ON and OFF a “water hammer” effect occurs, similar to the reverberating noise the pipes in your house make when shutting the water off abruptly from a faucet. To verify normal noises during use, compare the sound to another like vehicle, if available. If injector noise is determined to be excessive or irregular, use a listening device to isolate the noise to a particular fuel injector(s).

FIGURE 12-3 A GDI injector operates at a higher voltage and a higher pressure than a conventional fuel injector. Verify which fuel delivery type is used on the vehicle as part of your noise diagnosis. © Jones & Bartlett Learning.

Top-End Engine Noise A clicking or light tapping noise that gets louder with engine rpm is most likely a lifter or valve train noise. Top-end noises have several causes: low oil level or pressure, worn or damaged parts, or if the vehicle has mechanical lifters, excessive valve lash. An engine with mechanical lifters will require the valve cover removal and checking or adjusting the clearances following the manufacturer’s recommended procedure.

Verify oil level and condition when beginning your engine noise diagnosis. If the oil level was low, retest after adding oil. If the noise is still present, check base-engine oil pressure. The top end of the engine is typically last on the lubrication circuit, so low oil pressure has a pronounced effect on valve train components. Camshaft and valve train concerns are common sources of top-end engine noise, such as ticking, knocking, or rattle. These sounds occur during every other turn of crankshaft (camshaft speed is one-half of crankshaft speed) rotation. The frequency of the noises, therefore, will be slower than engine rpm. Placing an engine ear or stethoscope on the valve cover bolts will help isolate a top-end valve train noise. Move the tool around the valve cover, and if a V-type engine, test for noises on the opposite bank as well. If you are verifying the noise is coming from under a valve cover, the cause needs to be determined. To pinpoint the source of the noise, remove the valve cover(s) and visually inspect for wear, loose components, or out-of-adjustment valves, if applicable (FIGURE 12-4). If the visual inspection fails to turn up a result, using caution due to hot pressurized oil, run the engine with the valve cover to isolate the noise if possible. Do not operate the engine for extended periods of time with the valve covers off. Doing so could lead to loss of oil and a potential combustible (liquids that burn at temperatures above working temperature) hazard created when engine oil (even synthetic) contacts the hot exhaust manifold.

FIGURE 12-4 Inspecting the components on the top end of the engine will help the technician determine whether there is a mechanical fault, or on engines requiring valve lash inspection, a clearance issue that requires adjustment back to specification. © Jones & Bartlett Learning.

TECHNICIAN TIP

Some engines require valve lash adjustments at prescribed service intervals. Verify valve clearance if there is top-end noise on these types of engines. Adjusting the clearance back to specified values may eliminate the noise issue.

Not all noises that occur with every other crankshaft revolution are top-end noises. Since a power stroke occurs only with every other crankshaft revolution in a four-stroke engine, piston slap can also be the cause of noise occurring at half of crankshaft speed. Piston slap occurs at the top of the power stroke from the piston striking the cylinder wall during the initial combustion event, becoming significantly more audible as the piston-to-cylinder wall clearances increase due to wear. Piston slap is typically loudest after a cold engine start (engine OFF for 6 to 8 plus hours) with light to medium acceleration. As the engine reaches operating temperature, the pistons expand, reducing the piston-to-bore clearance, and therefore the noise. TECHNICIAN TIP Piston slap diagnosis. Engines using aluminum pistons and cast-iron blocks experience different expansion ratios when the engine is started cold that change as it warms to operating temperature. Aluminum expands approximately five times faster than cast iron, requiring larger clearances when cold. The additional clearance results in the hollow piston slap sound being louder with a cold engine. As the engine warms, the piston expands, reducing the clearance, and the noise subsides. To verify the noise is piston slap, with a cold engine, start and run it for 15 to 20 seconds. Listen, and remember the sound and intensity of the noise. Shut the engine OFF, remove all the spark plugs, and add a couple of squirts of oil into each cylinder. Reinstall the spark plugs, start and run the vehicle again, and compare the noise levels before and after adding oil. The addition of the oil reduces the clearance of the piston to cylinder wall briefly. If the oil significantly reduces the noise level for about 30 seconds, the noise is piston slap. If there is no difference, piston slap is not the cause of the noise, and additional diagnosis is required to find the cause.

Bottom-End Engine Noise Bottom-end noises are typically a louder, deeper, ticking or knocking noise due to the weight of the components involved. Bottom-end noises occur with every crankshaft revolution. Common sources of a bottom-end noise include the crankshaft, connecting rod(s) and bearings, piston pins, and damaged piston rings. To determine whether the noise is coming from the lower end, place the listening tool against the oil pan or the lug bosses on the cylinder block. A noise that is the loudest when testing from a boss is an indication of a bottom-end noise requiring some engine disassembly to inspect for damage and wear of the components.

Front-of-Engine Noise Engine noises that originate from the front of the engine can be internal or external. Common causes of a squeal, chirp, whine, or hoot noise originating from the front of the engine usually indicate a faulty frontend accessory drive (FEAD) component. To isolate the noise to a FEAD component, remove the belt(s) and operate the engine. If the noise is no longer present, visually inspect all the FEAD components for wear, signs of rust from failed bearings, and the drive belt(s). Belt noises can occur from contamination by coolant, oil, power steering fluid, chemicals, and mud. A badly worn belt can cause a squeal due to a lack of tension, or make a ticking, tapping, rattle, or whining noise. Another testing method involves spinning the pulleys by hand and checking for looseness or by attempting to rock the pulley back and forth (FIGURE 12-5).

FIGURE 12-5 Accessory drive belts, tensioners, and pulley bearings may be the source of engine noise. © Jones & Bartlett Learning.

The process for FEAD noise detection includes the following steps: 1. Remove the accessory drive belt(s). 2. Perform a visual inspection and spin all moving components by hand, feeling for and listening for any roughness or binding as well as a loose pulley indicating a bearing failure. 3. If the visual inspection does not produce a fault, start the engine. 4. Increase the engine rpm to where the symptom occurs. 5. If the vibration/noise is duplicated during this test, the belt(s) and accessories are not sources. 6. If the vibration/noise is not duplicated during this test, install the accessory belt(s), one at a time, to help locate the source. 7. Visually inspect the vibration damper for separation at the rubber/elastomeric damper; if the damper has failed, the engine’s power pulses will be transferred to the belt tensioner and can create a belt squeal and/or excessive serpentine belt movement and slap. Internal front-of-engine noises are usually a ticking, tapping, rattle, or slapping noise from timing drive components. Use the listening device on the cover bolts or bosses to isolate the noise. Removal of the engine front cover may be necessary to inspect internal engine components. Overhead camshaft engines often use long timing chains with hydraulically actuated timing drive components to keep the proper tension on the chain. A lack of oil pressure or a leaking hydraulic tensioner prevent correct timing chain tension, increasing wear and noise. As the timing drive components continue to wear, the timing chain becomes longer, until the tensioner is unable to reduce the slack anymore, resulting in timing chain slap and knock. Reduced tension also causes the timing chain to smack against the nylon timing chain guide, instead of running smoothly against it, increasing wear. An overtensioned timing belt or a failed

timing belt tensioner or idler pulley can cause a whining/whirring noise that increases with rpm. TECHNICIAN TIP A squeak that varies with rpm and load may be due to a failed front damper. The squeak occurs as the damper rotates. Replacement of serpentine belt(s), tensioners, and other FEAD components, or applying belt dressing, will fail to change the sound.

Additional Front-of-Engine Noises Manufacturers are turning to specialized alternator pulleys to reduce belt-drive system vibrations, increase belt and tensioner life, and improve engine efficiency. Decoupler pulleys are high-tech pulleys that provide belt-drive power to the alternator during acceleration and cruising speeds. During deceleration they decouple (or disengage). The decouplers’ design intent is to remove the stress placed on the belt and tensioner that occurs on a solid pulley alternator. During rapid deceleration, the rotating mass of the alternator opposes the force of the engine and continues to drive the system forward. By continuing to power the system forward, the rotation places additional stress on the belt and tensioner, requiring additional tension to prevent the belt from slipping. One-way clutch (OWC) pulleys and the overrunning alternator decoupler (OAD) both appeared in the late 1990s, collectively referred to as alternator decoupler pulleys (ADP) (FIGURE 12-6). The OWC was the first method to allow the alternator to freewheel on deceleration, followed by the OAD. The OWC and OAD operate by locking in one direction but freewheeling in the other. The OAD system is more advanced than the OWC and includes a tuned spring to dampen natural belt vibrations.

FIGURE 12-6 This OAD pulley allows for the limiting of vibrations of the drive upon engine deceleration. © Jones & Bartlett Learning.

OAD pulleys produce various front-end engine noises mistakenly diagnosed as an internal engine fault. Grinding, knocking, and buzzing noises are common when an OAD fails internally, or because of a failed bearing. ADPs are normal wear items and have an expected service life that matches the belt, depending on their use. Some decoupler pulleys are serviceable separately whereas others require alternator replacement. Refer to a parts listing for the vehicle being serviced. When servicing the belt, replace the OAD and belt tensioner also. Replacing these components is often overlooked, causing noise issues later. The most common noise is a buzzing noise during shutdown resulting from a failed bearing. To diagnose a bearing, bring the engine speed to 2500 rpm and shut the engine OFF while at this speed. Listen for a buzzing noise lasting for approximately 5 to 10 seconds after shutting the engine OFF. If a buzzing is heard, and found to be coming from the ADP, replace the decoupler if available, along with the pulley, belt, and tensioner. OEMs do not sell the decoupler separately. However, it is available in the aftermarket and requires special tools for replacement. Follow the instructions for replacement supplied with the pulley. Other noises that occur are a grinding or knocking noise that varies with accessory load. Additional loads from the air-conditioning (A/C) compressor or the power steering pump during a tight turn may cause the noise to occur or intensify. Misdiagnosis of the fault as the accessory often occurs since the noise occurs or becomes louder when engaged. A light knocking or grinding noise from a failed OAD

combined with an engine performance problem can be incorrectly identified as an internal engine concern. To diagnose, remove the pulley cover to gain access to the center of the pulley for additional testing of the OAD using the special tools from the kit. After removing the cover, inspect for metal shavings, indicating an internal OAD failure. Install the proper tool from the kit and place it on the alternator shaft. Using a torque wrench attached to the tool, turn the pulley in both directions. Rotational torque in the drive direction specification is 9 to 13 in-lb, including a spring feeling during rotation of an ADP pulley. Both decoupler pulleys should rotate freely in one direction and lock in the opposite direction. An OAD design will have a spring feel due to the tuned spring. If the OAD pulley slips in the drive direction, spins freely in both directions, or locks when turning in both directions, it requires replacement. Failure of the pulley to operate correctly may produce a knocking or grinding noise.

Rear-of-Engine Noise A cracked or loose flywheel/flexplate is a common cause of noise originating from the rear of the engine. In some instances, the cracks are visible using a borescope after removing an inspection plug or starter. To check, attempt to turn over the engine manually using the flywheel or flexplate while feeling for excessive looseness. If access is limited, or the borescope procedure is inconclusive, removal of the transmission for a visual inspection may be required. Some engines may have timing drive components at the rear of the engine, which can be the source of noise (ticking, knocking, or rattle). Use an engine ear or stethoscope on the rear of the engine if you suspect the noise is internal to the engine (FIGURE 12-7). Remember to move the listening device around to try to find where the noise is the loudest. Place the listening device on solid objects, not covers, to help find the noise. If you determine the noise is internal to the rear of the engine, some disassembly may be required to inspect for wear or damage.

FIGURE 12-7 An engine ear or stethoscope can help you find the source of a noise in the engine.

Using the Speed of the Noise to Isolate a Fault To aid in correctly identifying an engine noise, pay attention to the engine rpm when the noise is occurring. Valve train noises are generally loudest up to approximately 1500 rpm. Rod knocks are the loudest when increasing load and rpm, usually at speeds over 2500 rpm. Rod knock intensifies by increasing and decreasing rpm between 2500 and 3500 rpm. Known as “feathering” the accelerator pedal, this often creates a distinctive double knock due to increased rod bearing clearances as the crankshaft changes speed.

Valve Train Noises 12-2 Isolate the cause of top-end engine noise.

Valve and hydraulic lifter noise produce a clicking sound at half of engine speed, most noticeably at idle when oil pressure is at its lowest. Typically, as rpm climbs, oil pressure increases, reducing the noise. The primary causes of valve train noises are increased clearances due to wear, misadjusted mechanical lifters or shimmed buckets, or a faulty hydraulic lifter. A clicking or tapping noise that increases with engine speed to about 1500 rpm is typically valve train or lifter/follower noise. A low oil level, sludge, or dirt and contamination of the oil are the primary causes of valve train noises. Low oil pressure is the second most common cause of top-end noises. Verify oil level and condition first. Use caution when attempting to clean a severely sludged engine by flushing. The possibility of overloading and plugging the oil filter during the cleaning process exists. A clogged oil filter results in oil bypassing the filter, causing significant internal engine damage that was not present before flushing. The best method for sludge removal, assuming it is not excessive, is to allow the engine oil to perform the cleaning gradually, over a period of time. To clean the engine, slowly increase the rate of oil and filter changes. However, if sludged badly enough, cleaning may not be an option, leaving engine replacement as the only option. Valve train noise, besides being an audible concern, also restricts the engine from creating power. When a valve train noise is present, the valve timing events are not correct, resulting in a loss of performance and a rough idle, or misfire, due to excessively loose or tight valve lash. Low oil pressure can also cause tapping noises. The valve train is at the end of the lubrication circuit, and as pressure drops it affects the top end of the engine significantly. Low oil pressure also traps air in hydraulic circuits such as a lifter, resulting in excessive clearances between the camshaft and the valve train, causing tapping or clicking. Varnish from poor oil maintenance can also cause the clearances to increase due to sticking components. Incorrect oil viscosity or contamination of the oil from sludge can lead to increased wear, galling, or seizing of followers, rocker arms, or pushrods; this eventually leads to valve train clicking or chattering noises. Adjustable valves require periodic maintenance. Loose valves cause tapping noises. Tight valves are quiet. Valves that are too loose open later, close earlier, and restrict the amount of air pulled into the engine. If the intake valves are too tight, they open too soon and stay open too long (close late), allowing more air into the cylinder than needed. Exhaust valve problems offer similar results: when loose, they open later and close earlier, trapping excessive air into the cylinder. Exhaust valves that are too tight open too soon and stay open too long. Tight valves limit when the valve is seated, reducing important contact time with the valve seat (FIGURE 12-8). Seat contact time allows heat to transfer from the valve to the cylinder head. Insufficient valve seat time overheats the valve, leading to burning.

FIGURE 12-8 Periodic valve adjustment allows for the engine to operate at peak efficiency, thus increasing performance and mileage. © Jones & Bartlett Learning.

To verify valve train noise, remove the valve cover(s) if accessible. Start and run the engine with the valve cover off. Continue inserting feeler gauges between each rocker arm/follower and valve tip, increasing the thickness until reducing or eliminating the noise. TECHNICIAN TIP When adjusting valves, it is better to err on the side of caution, by setting the valves a little loose rather than too tight. Exhaust valves that are too tight will not stay seated in the head long enough to dissipate heat, leading to a burnt valve.

Timing Chain Noise The timing chain is located at the front of the engine and attaches to a set of gears that connects the crankshaft to the camshaft(s) (FIGURE 12-9). The camshaft(s) and crankshaft both have gears, also known as sprockets, that engage the links in the timing chain. Timing chains (or belts) and gears maintain the correct relationship between one or more camshafts and the crankshaft. The gears are positioned on the camshaft or crankshaft with a keyway or locating dowel. Other designs do not use a key or dowel and rely only on the clamping force of the attaching bolt and a diamond washer. Some engines may have an additional timing chain at the rear of the engine connecting a jackshaft to the camshaft.

FIGURE 12-9 Timing chains stretch and wear over time, and related components, such as the guides, also wear over time and can fail, leading to front engine noise. © Jones & Bartlett Learning.

Teeth on the camshaft and crankshaft gears mesh with teeth on the timing chain to maintain timing. The opening and closing of the valves must be timed to the crankshaft rotation. Precise synchronization of the camshaft and crankshaft (sync) is necessary for combustion. Modern engine design has trended toward increasing the use of overhead camshaft engines. Overhead camshaft engines may be either a single overhead camshaft (SOHC) or a dual overhead camshaft (DOHC) design. Moving the camshaft(s) to the top of the engine has increased the length of the timing chain and the complexity of the timing chain tension arrangement. Most designs use a timing chain tensioner(s) and nylon chain guides to maintain the correct tension on the chain resulting from normal wear and to reduce noise. The chain guides may be fixed or movable, and they aid in controlling harmonic movement caused by the length of the chain. Most engines use a fixed guide on the drive side of the chain that connects to the camshaft. A movable guide is located on the idle side of the chain and usually includes a tensioner. Tensioners operate off either oil pressure or spring tension to maintain the proper adjustment on the drive side of the chain. Over time the timing chain can stretch and wear, tensioners can fail, and chain guides can break. Timing chains are designed to last longer than a timing belt but require proper maintenance to prevent issues from occurring. Timing chains are primarily one of two designs: a double roller or silent type. Steel rollers act as a bearing as the chain moves over the gears and guides. Using roller chains reduces friction and wear on the gears. Roller chains are dependent on oil that is clean and the correct viscosity. Debris and grit, a result of improper maintenance, will cause accelerated wear. Silent chains offer reduced costs to manufacture and produce less noise during operation. Therefore, silent chains are found on most current engines. During operation, the silent chain slides against the gear instead of rolling

over it. Pins hold the links together on a silent chain, allowing the chain to pivot between the links. Silent chains are also more flexible that roller designs. Total timing chain failure breakage is rare; however, elongation or stretch is common. Roller chain wear occurs in the supports. As the silent chain wears, slack develops at the pivot points where the pins hold the links together. The links do not wear. Instead, the holes that the pins pass through in the links and the pins themselves wear. The timing chain and nylon guides wear during normal operation. Tensioners take up the slack on the idle side of the chain, helping to keep the chain tight. Chain tensioners have a limited range of movement. Eventually, the chain stretches or the guides wear beyond the ability of the hydraulic tensioner to take up the slack, and the timing chain begins to rattle. A tensioner will not restore cam timing or prevent noise in a stretched chain. The chains eventually become so loose they whip back and forth against the guides, and possibly the timing cover, causing the noise. The constant slapping of the loose chain can eventually lead to failure of the guides, tensioner, or chain. Timing chain noise is most prominent on startup. A failed tensioner, low oil pressure, or an oil filter that does not contain an anti-drainback valve may cause the timing chain to jerk or make noise when starting the engine. The jerking increases wear of the guides and chain and may break the nylon guides. If timing chain wear is not excessive, the noise may decrease as oil pressure increases. Building oil pressure moves the hydraulic tensioner out, taking up the slack in the chain. Oil pressure is low initially after starting, and then builds as the pump pushes oil through the engine. Often, after the engine warms up, the intensity of the noise will decrease or dissipate completely as oil pressure builds and the oil thins, flowing better. If the noise disappears or diminishes after running for a few minutes, the tensioner is just hiding it. A problem still exists with the timing chain or guides, requiring attention. An excessively loose timing chain, arising from a failed tensioner, chain guide, or a stretched timing chain, often produces a knocking noise when the chain hits the cover or guides (FIGURE 12-10). The sound is metal-to-metal contact or a metal-to-nylon slapping, knocking noise. The sound can be constant or intermittent. Failure to repair the fault may result in metal contamination of the engine oil as the chain wears into the cover. Tensioners and guides fail from contaminated oil, or low oil pressure, preventing the hydraulic components from operating correctly. Damaged timing chain gears with missing or broken teeth can cause a ticking, tapping, or rattling noise. Excessively worn or damaged chain guides, or a faulty tensioner, result in erratic cam timing and poor engine performance. A loose or stretched timing chain results in erratic engine performance as the camshaft-to-crankshaft timing is constantly changing from incorrect tension. A loose or stretched timing chain will result in retarded cam timing.

FIGURE 12-10 A loose timing chain can cause a front-engine noise. The cause may be a chain that has stretched beyond normal limits or is damaged, or worn or damaged chain guides and tensioners. © Jones & Bartlett Learning.

Causes of premature chain or tensioner failure are commonly lubrication related. Improper oil viscosity, extended maintenance intervals, or a lack of oil changes are the primary culprits. Cheap, inferior oil filters failing to catch debris are another cause of oil-related issues. Manufacturers may specify only a synthetic oil to meet the lubrication requirements of an engine. Oil that fails to meet the required specifications will cause timing chain wear. Proper oil use is even more critical on GDI engines. GDI engines place an extra load on the timing chain by using a camshaft-driven high pressure fuel pump. Engine designers have switched to low viscosity synthetic oils, which produce quicker oil flow while reducing friction. Low viscosity oil flows faster than heavier oil, especially when cold. The lower viscosity synthetic oil pressurizes the hydraulic tensioner quickly on startup, keeping the chain tight, reducing breakage, and helping to prevent the chain from jerking or jumping time. If a timing chain noise is suspect, check the oil level and quality. To diagnose possible timing chain noises, use a stethoscope or an engine ear. Place and move the probe on the top and sides of the timing chain cover. If you hear a metal-to-metal scraping, slapping, or knocking sound behind the cover, suspect a loose timing chain. Install a manual oil pressure gauge, and check base oil pressure when the engine is at operating temperature. If the oil pressure is within specification, engine disassembly will be required to verify and repair the problem. To correct, replace the tensioner(s), chain guides, and timing chain. Inspect the cam and crankshaft sprockets for wear; look for missing, damaged, or sharp teeth and, if necessary, replace any worn sprockets.

Motor Mount Faults 12-3 Isolate motor mount failures.

Motor mounts support the vehicle’s powertrain while insulating the passengers from noises and vibrations produced while the engine is running. All engines and transmissions generate both noise and vibration due to reciprocating components. Typically, the engine’s vibration characteristics are most noticeable at idle. Shifting gears causes the most noticeable movement. The powertrain mounts act as an insulator to control both of these issues. When a mount fails, it typically transmits the noise and vibration to the passengers. A mount that fails can also induce problems other than vibration and noise due to excessive movement of the powertrain. Transverse mounted engines (sit sideways in the engine compartment) also usually incorporate strut rods to control engine movement when placing the vehicle in gear, and during acceleration or deceleration. When placing the transmission in gear, torque passes through the engine to the transmission, causing the powertrain to rotate. When putting the transmission in drive, the front of the engine lifts, pulling on the front mount while placing downward pressure on the rear mount. When shifting the transmission into reverse, the load changes, and now torque lifts the rear mount while pushing down on the front mount. The addition of torque or strut rods limits this movement and helps prevent damage to the motor mounts. Worn or damaged motor mounts allow excessive movement of the engine, creating abnormal noises or a loud bang and harsh engagement when placing the transmission in gear. Contact can also occur between moving and stationary components while driving the vehicle, due to worn mounts. Tearing of exhaust flex pipes or the fresh air inlet tubing is often a result of excessive engine movement also. Motor mount technology has and continues to evolve. Older, rear-wheel-drive vehicles with inline engines commonly used a simple three-point mounting system of a rubber block mounted between two pieces of steel. A mount was located on each side of the engine, with a third mount in the center of the transmission tail shaft. Newer vehicles may use hydraulic, hydroelastic, hydromounts, or active motor mounts. Hydro-style mounts have a hollow chamber that is typically filled with hydraulic fluid (some may use a glycol fluid) to absorb and reduce vibrations, preventing transmission to the chassis and passengers. These mounts are found most often on 4-cylinder and V6 engines, along with some diesel engines, due to their inherent rough idle qualities. They may also appear, however, on luxury vehicles, which use larger engines, to increase the level of satisfaction associated with those vehicles. Some higher end mounts use an internal valve similar to a shock absorber, or an electronic solenoid, to change the mount’s ability to dampen vibrations that vary with engine rpm.

Diagnosing Standard Motor Mounts Several methods exist to test and verify motor mount operation. Before testing, perform a visual inspection. Check for loose or cracked brackets, missing bolts and nuts, and collapsed or torn rubber in the mounts. Inspect for fluid leaks. Oil and power steering fluid may degrade the rubber over time, tearing or collapsing it under engine torque. Check hydro-mounts for fluid leaking from the mount itself, which is an indication of failure. Using a pry bar to check the mounts, apply pressure while watching for movement, separation of the rubber from the metal, or physically broken motor mounts; these are also unacceptable. After the visual inspection, additional testing may be required. One test involves two technicians; one watches the engine while the other shifts the vehicle from drive to reverse slowly and repeatedly (FIGURE 12-11). While performing this test, ensure the parking brake is applied, chock the drive wheels, and apply the service brakes. Another test involves brake torqueing the engine in gear while watching for excessive movement. Remember that the engine mount design is intended to allow slight movement up

and down; this does not indicate a failed mount. In the case of excessive movement, however, suspect a probable mount failure.

FIGURE 12-11 Standard motor mounts can fail, causing noise during acceleration as the engine lifts off the mount. © Jones & Bartlett Learning. Photographed by Keith Santini.

SAFETY TIP Follow all safety precautions when performing these procedures. Apply the emergency brake, and have an assistant keep a foot on the brake at all times. Stand to the side of the vehicle, not directly in front of it, while watching the engine. Due to cramped engine bays with limited visibility, perform the transmission engagement test with the vehicle on a rack, in the air, without loading the engine. A view from underneath may allow monitoring of mounts that are difficult to see from the top of the engine compartment. Have an assistant move the shifter, with a foot on the brake, while looking for excessive movement. Another method for detecting a broken motor mount is to lift the engine slightly using either a floor jack or large pry bar to eliminate or change an engine vibration. With the engine running, apply slight upward pressure on the engine using a floor jack. Install a block of wood between the floor jack and the engine to prevent damage to the engine. Use care when lifting the engine. The idea is not to raise the engine and lift it out of its mounts. Apply only a slight upward pressure, supporting a small amount of the engine’s weight, checking to see whether the vibration has altered. If the vibration and shake have changed, close inspection of the mounts will be required. Moving the block of wood and jack to different locations before performing this procedure may help to isolate the faulty mount. Use a pry bar to apply

slight pressure to the engine from the top side. Before prying, verify that the location of the pry bar will not cause damage to the engine or vehicle at the prying point. Placing a block of wood under the prying point will help protect the vehicle also. Do not pry on plastic or composite engine parts; use extreme caution around fluid lines and keep the pry bar away from moving components and belts when prying. Physical damage to the mounts does not have to be present to create a vibration. Improper installation of the mounts can create a binding in the rubber of the mount transferring engine vibrations to the chassis and then to the driver. Incorrect installation of the mounts or attaching hardware, or not allowing the engine to neutralize before tightening the bolts to the specification, can all lead to vibration transfer to the chassis. When replacing a mount, lift the weight from it before removal from the engine or transmission. Use caution when lifting the engine or transmission with an engine support bar, transmission jack, floor jack, etc. Use an insulator to protect the lifting point, and visually inspect the area to verify that no damage will result during the process. Verify the proper procedures in the service information. Some engine and vehicle combinations require removal of the intake plenum, radiator shroud, or cooling fan, allowing the engine to be lifted enough to gain the clearance needed to access and replace the mount, for example. Whenever replacing or tightening a mount after service, hand-tighten the attaching bolt and nuts. Start the engine and move the shift lever through the gears, pausing briefly in drive, neutral, and reverse. This procedure neutralizes the engine, transmission, and exhaust-preventing binding of the rubber mounts. Place the transmission back in neutral or park, shut the engine OFF, and torque the bolts and nuts to specification. Always draw the bolts and nuts down evenly to prevent binding. If servicing the exhaust system, follow the same procedure. Install and route the exhaust correctly using the equipped hangers. Hand-tighten the attaching bolts and nuts, start the engine, and operate the shifter through the gears to allow the exhaust to neutralize. Exhaust vibrations can transfer through the chassis similar to engine vibrations. After any mount or exhaust repair, drive the vehicle through a broad rpm range, varying the load on the engine to verify that a vibration or shake is not present.

High-Tech Motor Mounts To dampen and control engine vibrations, manufacturers are installing motor mounts that change stiffness based on engine speed. Controlled electronically by the PCM, “active” or “smart” mounts are switchable either hydraulically or electronically. The PCM activates a solenoid to control the mount’s movement before placing the transmission in gear during acceleration or deceleration. By applying a vacuum through the solenoid (usually done at idle), the mount becomes softer, providing additional dampening of the powertrain vibrations (FIGURE 12-12). At higher rpm, the mount stiffens, controlling unwanted engine movement.

FIGURE 12-12 High-tech drivetrain mounts are PCM controlled to cancel out vibrations, providing smoother operation. © Jones & Bartlett Learning.

Description When a hydro-mount fails, it loses its fluid, resulting in a significant loss of the amount of vibration movement it can control. Fluid seen leaking from a mount indicates it has failed and requires replacement (FIGURE 12-13).

FIGURE 12-13 A leaking hydraulic mount will cause it to fail, leading to abnormal vibrations and possibly noise when shifting into gear during moderate to high engine torque accelerating or when braking. © Jones & Bartlett Learning.

“Smart” mounts can use vacuum to control engine shake based on engine rpm. Another option for the smart mount is an electronically controlled motor mount. The electronic motor mount uses a combination of an acceleration sensor to monitor movement/shake and an electric actuator to control the amount of shake or movement in the engine. Vacuum-controlled mounts use a solenoid that regulates the amount of vacuum to the mount, changing its stiffness based on rpm. Applying vacuum to the motor mount at idle makes it more flexible, absorbing more of the engine’s pulses and vibrations. As rpm increases, the PCM removes vacuum, increasing the rigidity (stiffness) of the mount and preventing excessive movement. Any vacuum leak that occurs at the mount, vacuum line(s), or the vacuum storage canister frequently results in an increase in the engine’s vibration and shake at idle. Use a handheld vacuum pump to diagnose the system. Verify that the vacuum reaches the mount from the control solenoid and that vacuum holds at the mount, the supply line(s), and the reservoir. Any

leak will require repair or replacement of the failed component. If vacuum is not available at the motor mount, check control voltage, ground, and vacuum supply to the control solenoid. The solenoid is typically tested with an ohmmeter to verify the solenoid windings are not open. To offset movement, an electronically controlled engine mount uses several inputs, a module, and an actuator. The control module manages an actuator inside the mount, producing its own counter shake or movement. The movement created is exactly opposite of what the sensor is receiving, canceling out the vibration or shake created by the engine. Other inputs used for control of the mount include transmission selector range, coolant and air temperatures, engine load, and vehicle speed. Use a scan tool to check for codes. Diagnosis of these systems requires a high-level aftermarket or dealer-level scan tool to check for codes and perform the active motor mount actuator test.

Abnormal Combustion—Preignition and Detonation 12-4 Determine the cause of engine detonation and preignition.

Two abnormal conditions can happen in a cylinder during the combustion process: preignition and detonation. Preignition and detonation are words used interchangeably and incorrectly to describe a knocking, rattling, or metallic pinging noise heard during acceleration. Incorrect ignition timing from a secondary ignition source, not the spark plug, causes detonation and preignition. Both events occur at different times during the combustion process, causing abnormal combustion. Although very different, both tremendously increase the potential for extensive engine damage. Detonation differs from preignition in the timing of the event. Detonation occurs after the spark plug fires. Preignition occurs well before the spark plug fires. Unlike detonation, which produces a very loud knock, preignition is silent because there is not a rapid increase in cylinder pressure. Normal combustion occurs when the spark plug ignites the air-fuel mixture. During normal combustion, after ignition occurs, the flame front travels across the combustion chamber, increasing the temperature of the unburned gases and pressure in the combustion chamber. During normal combustion, there is not an explosion when the mixture ignites. The air-fuel mixture burns in an orderly fashion across the combustion chamber. The controlled uniform burning of the gases produces a steady rise in pressure consuming all of the air-fuel mixture.

Preignition Normal combustion is a controlled burn across the combustion chamber. The burning begins when the spark jumps the electrode gap at the spark plug, radiating outward. With preignition, something in the cylinder is glowing hot enough to act as a spark plug. Preignition occurs when the air-fuel mixture selfignites in the very early stages of the compression stroke, before the spark plug fires, igniting the air-fuel mixture. Early combustion causes the engine to attempt to compress a hot expanding gas for a significant portion of the compression stroke. The pressure wave created by the spontaneous, uncontrolled burning of the gases slows piston speed, attempting to force the piston back down the cylinder bore. Pressure waves acting on the top of the piston create a momentary backlash of the crankshaft while it is still rotating, trying to bring the piston up to top dead center (TDC). The tremendous increase in heat and load on the engine’s internal parts can cause catastrophic failure in a very short time. Preignition is not easily detectable because there is not an audible warning given. The lack of a sudden rise in pressure prevents a telltale knock or metallic rattle sound to inform the driver of a problem. There is just an intense amount of pressure and heat acting on the piston for a very long time. Normally the only warning received is when the engine quits running due to internal damage. Preignition often results in a melted, splattered, fused porcelain spark plug insulator, a missing or melted ground insulator, or a hole melted in the center of the piston (FIGURE 12-14).

FIGURE 12-14 A melted plug electrode is a major sign of detonation within the cylinder. © Jones &Bartlett Learning.

Detonation is not always destructive and can exist in an engine for a relatively extended period compared to preignition. Detonation can pound on the piston, rings, and cylinder walls over a long time depending on engine load, construction, and output. An engine with a higher power output is more susceptible to engine damage compared to a lower producing engine. Preignition is usually an instant failure of the engine. The only warning signs are generally white smoke from the exhaust followed by an

engine that stops running not too long afterward (TABLE 12-1). TABLE 12-1 Determining Cause of Detonation Causes of Preignition

Additional Explanation

Carbon deposits from oil entering the cylinder, failed valve seals, guides, rings, or cylinder walls

Carbon deposits can also be a result of the engine failing to reach normal operating temperature, creating incomplete combustion of the air-fuel mixture

Poor fuel quality or incorrect octane rating Glowing carbon deposits on a hot exhaust valve Engine running hotter than normal/coolant temperature too high

A valve that runs too hot because of insufficient seating, a weak valve spring, or insufficient valve lash Low coolant level Stuck closed thermostat Restricted airflow across the radiator Slipping fan clutch or serpentine belt Defective electric cooling fan Other cooling system problem causing engine to run hot

Spark plug that is not the correct heat range causing an overheated spark plug Loose spark plug that fails to transfer its heat to the cylinder head creating a source of heat for preignition Sharp or jagged edge in the combustion chamber or on top of a piston

Grinding sharp edges smooth and round can eliminate this cause

Lean fuel mixture Improperly ground valves without enough margin causing sharp edges on valves

Detonation Detonation is often confused with preignition. Technicians frequently use the terms interchangeably and incorrectly to describe a metallic noise from the engine. The symptoms are similar—a pinging sound on acceleration—but detonation is different from preignition. Both concerns produce an unwanted ignition event in the cylinder that can lead to severe engine damage if not repaired. Normal combustion occurs when the spark plug ignites the air-fuel mixture. During normal combustion, after ignition occurs, the flame front travels across the combustion chamber, increasing the temperature of the unburned gases and increasing pressure in the combustion chamber. The controlled uniform burning of the gases produces a steady rise in pressure, consuming all of the air-fuel mixture. When detonation occurs, the spark plug ignites the air-fuel, as it should; however, the flame front initiated by the spark plug collides with an undesired flame front. Detonation begins a few degrees before TDC and is an explosion of the end gases after normal combustion has started. Near the end of combustion, unburned areas of air-fuel mixture are now superheated and compressed to a pressure that exceeds the self-ignition limit. The remaining air-fuel mixture ignites in an uncontrolled manner, creating a pressure spike in the cylinder (FIGURE 12-15). Detonation can increase normal combustion chamber pressure up to 300 times above normal. The extreme spike creates violent shock waves, producing an audible knock caused by the piston rattling in its bore. The pressure wave unseats the rings and transfers the severe impact load to the connecting rod, traveling down to the upper rod bearing and into the crankshaft. The extremely high pressures can damage head gaskets, pistons, rings, and bearings (TABLE 12-2).

FIGURE 12-15 When combustion happens without control, the results will cause the components that are affected by this detonation to become severely damaged by this situation. © Jones & Bartlett Learning.

Description TABLE 12-2 Detonation Indicators Mechanical damage: piston rings and lands

Fractured spark plugs and ring lands Normally the first or second land is damaged A broken second ring land on a piston is typically a sure sign of detonation

Overheating: scuffed piston skirts from high cylinder or coolant temperatures

This is known as four-corner wear. Excessive heat causes the skirt to deflect but the pin boss area does not and is driven into the cylinder walls by the force of the pressure waves on the top of the piston. Therefore, inspect for wear on both sides of the piston wrist pin on each side of the skirt.

Abrasion: pitting on the crown of the piston

Appearance similar to sand blasting the surface The mechanical pounding erodes the piston crown Normally found at the point of the piston farthest from the spark plug Or by the exhaust valves as a result of end gas combustion

Causes of Detonation There are a lot of situations that cause detonation within a cylinder. As diagnosis progresses for the vehicle, the technician must take these potential situations into account when fixing the engine. Following are some of the causes of detonation that can cause the engine to combust prematurely. With this uncontrolled combustion, engine misfire and running issues can be felt. Carbon deposits. Accumulating carbon deposits on top of the piston or in the combustion chamber increase the compression ratio. Carbon deposits are a common cause of detonation in highmileage vehicles. Oil that enters the combustion chamber creates carbon deposits when partially burned. These deposits can affect valve seals, valve guides, worn or damaged piston rings, cylinder wall wear, incorrect or improperly operating positive crankcase ventilation (PCV), or crankcase orifice increasing crankcase pressures. Carbon deposits can be removed with a chemical top engine/induction cleaner. Use caution with these cleaners and verify that the manufacturer approves, particularly on turbocharged vehicles. Lean air-fuel mixture. Rich mixtures lower combustion chamber temperatures resisting detonation; lean air-fuel mixtures increase the combustion chamber temperature. Causes of lean air-fuel mixture include: Vacuum leaks at the intake manifold or vacuum lines or power brake booster, low fuel pressure or volume, restricted fuel injectors, or a restricted fuel filter Contaminated or biased mass airflow (MAF) or manifold absolute pressure (MAP) sensor Biased/incorrect barometric pressure (BARO) sensor A poor quality or the wrong air filter affecting airflow over the MAF sensor Excessive boost pressure. Uncontrolled or excessive boost will raise cylinder pressures well above the intended range. Inspect wastegate operation for failure to bleed off pressure when reaching maximum designed pressure. Excessive boost pressure may also come from: Incorrect or failed solenoid boost control solenoids, control circuits, or powertrain control module (PCM) Biased or failed MAP sensor Restricted intercooler that fails to reduce the temperature of the incoming compressed air Verify use of the correct octane fuel. Most engines use 87-octane fuel. High compression, highperformance engines may need a higher octane. If the vehicle requires 87-octane fuel and switching to a higher octane eliminates a constant detonation problem, this is not a repair; find the cause of increased cylinder pressures, lean air-fuel mixture, or increased engine temperatures. Alcohol may also be an issue. Check EGR operation, if equipped. EGR reduces NOx by lowering cylinder temperatures with the addition of an inert gas that does not burn. Detonation may be caused by an inoperative EGR valve or control system or by EGR passages plugged with carbon. Incorrect or stuck variable valve timing (VVT) operation. Keeping the camshaft(s) overadvanced increases cylinder pressures. Check for overadvanced ignition timing, if adjustable. Overly advanced ignition timing causes cylinder pressures to increase rapidly. Check knock sensor operation. Most late-model engines use at least one knock sensor that

responds to frequency vibrations created when detonation occurs. The knock sensor produces a voltage and sends it to the PCM, which retards timing until detonation stops. Some manufacturers use one knock sensor per cylinder, which enables the PCM to control spark timing by cylinder. On vehicles using coil-on-plug (COP) ignition systems, the ignition timing can be altered on a cylinderby-cylinder basis instead of retarding timing for all cylinders. Check the engine for overheating or running above specification. An engine that is operating above normal temperature can cause detonation and preignition. Air pockets from a low coolant level, or a failure to “burp” the cooling system of air after opening the cooling system could cause a problem. Use a vacuum fill tool after servicing the cooling system to remove any air pockets. Steam does not transfer heat from the cylinder walls to the water jackets; instead, it acts as an insulator. Check the cooling fan(s) operation and inspect for a stuck closed thermostat, restricted radiator or airflow over the radiator, low coolant level, water pump impeller loose or eroded from cavitation, missing or broken fan shroud, and excessive cooling system contamination that insulates the cylinder to water jackets instead of transferring the heat. Check spark plug for the incorrect heat range. If the heat range is too “hot,” detonation and preignition can occur. Spark plugs with a blistered or yellow electrode are indicators of an overheated spark plug; verify the correct plug is installed. Faults created by a technician or owner include the following: Changing the wastegate operation using an adjustable wastegate or a programmer Increasing compression by installing higher compression pistons, milling the cylinder head (reduces the combustion chamber size, increasing compression), indexing the camshaft in an overly advanced state, or boring the cylinders oversize Lugging the engine with a manual transmission, downshifting to a lower gear

Oil Consumption Testing 12-5 Interpret engine fluid issues affecting engine performance.

All engines consume oil; it is essential to provide lubrication to the cylinder bore walls, pistons, and rings. Excessive oil consumption indicates excessive engine wear or damage. Perform an oil consumption test to verify excessive oil usage. Most manufacturers will specify the maximum allowable use. In many cases, the specification is no more than 1 quart in a certain number of miles (FIGURE 12-16). As long as the consumption is less than the specification, no action is necessary. The color of the exhaust may offer clues for oil usage that is not visible as a leak. If the color has a blue-gray tint, it indicates the engine is burning oil. Causes of excessive oil consumption include worn valve seals and valve guides with excessive clearance, worn or sticking piston rings and worn cylinder walls, a damaged turbocharger, or a stuck closed PCV valve or plugged crankcase orifice. It is possible for an engine to burn oil that offers no visible smoke during normal operation. Therefore, to verify oil consumption, perform an oil consumption test. Most OEMs require that a consumption test is run and fails before performing any warranty repairs.

FIGURE 12-16 Each manufacturer has different requirements for engine oil consumption, so the technician should refer to service information to find out what the particular specifications are for the vehicle in the facility. © Snap-on Incorporated.

The customer should check or have the oil level checked every 200 miles. When the oil level falls below the minimum mark, indicating a quart of oil has been used, add oil to the engine, and then calculate the accumulated elapsed mileage (FIGURE 12-17). Depending on the manufacturer, the distance used to determine excessive consumption varies. Mileage ranges for oil consumption are between 900 and 1500 miles. Some manufacturers state that 600 to 700 miles is reasonable. Always

refer to service information for the proper specification. If the oil usage falls below the guidelines, excessive oil consumption may be present. Some manufacturers require extended testing over a set time or mileage to verify the consumption concern.

FIGURE 12-17 When doing an oil consumption test, make sure you check oil the proper way as explained in the oil consumption test procedures. © Jones & Bartlett Learning.

Oil Pressure Testing Low base-engine oil pressure can cause engine damage and create engine performance issues. Performance issues are particularly noticeable on VVT and lift engines. Turbocharged vehicles are also dependent on proper oil pressure to keep the bearings lubricated and cooled. As engines gradually wear, a slight reduction in oil pressure is expected. A sudden or excessive loss of pressure calls for testing to determine the cause. Diagnose and repair low oil pressure concerns as quickly as possible to prevent long-term engine damage. Indicators of an excessive loss of oil pressure include: Poor engine performance Engine noise An instrument cluster gauge or light indicating low oil pressure Oil pressure testing provides valuable information about the engine’s lubrication system, engine bearing clearances, and overall engine health. Checking oil pressure is a quick test to determine the wear of internal engine components. Install a mechanical gauge, typically in the oil sender port, to measure oil pressure (FIGURE 12-18). The use of the instrument cluster gauge is not a valid test. Instrument cluster gauges are not calibrated. Also, some oil pressure gauges are simply an ON/OFF

switch that functions as a gauge. Additional ports may be located in the cylinder head offering added locations for oil pressure testing. Typically, the oil pressure at the cylinder head is slightly lower than at the oil sender port in the engine block. Comparison of the two pressures may indicate low oil pressure at the cylinder head, a common cause of VVT concerns.

FIGURE 12-18 A mechanical oil pressure gauge is installed in place of the oil pressure sending in parallel to the oil pressure sending unit for an actual pressure measurement. © Jones & Bartlett Learning.

Always refer to manufacturer recommended procedures and specifications when testing base oil pressure. If a specification from the manufacturer is unavailable, a rule of thumb is a minimum of 10 psi per 1000 rpm. In other words, oil pressure at 2000 rpm should be a minimum of 20 psi. In all actuality, most engines develop far more oil pressure than this. Typically, manufacturers recommend the engine at operating temperature checking the pressure at idle and again at 2000 rpm. A preferred version checks the oil pressure over time. Do not install the gauge and walk away while the engine reaches normal operating temperature. Ideally, starting with a cold engine monitoring the pressure over time improves diagnosis. If oil pressure remains low for an extended period after starting, suspect a check valve concern allowing oil pressure to drain back into the pan after shutting the engine down. If oil pressure is acceptable after a cold start but drops when the engine is hot, suspect an internal leak; excessive bearing clearances, a partially stuck check valve or pressure valve, a failed O-ring, and a leak on the suction side of the pump are all possibilities. When oil pressure drops off slowly as rpm is raised, then returns to normal after shutting the engine OFF and waiting a few minutes before restarting, suspect and inspect for oil pickup contamination. Low oil pressure is usually associated with excessive rod or main bearing clearances, which

commonly occur as the engine wears. Cam bearing clearance, often overlooked, can also cause low oil pressure. Oil pump wear in modern engines is uncommon, though a problem can still occur. If an engine has excessive metallic or carbon contamination or suffers a timing chain tensioner/guide issue, inspect the oil pump for damage. Sticking oil pressure relief or check valves reduce oil pressure to the engine’s lubrication passages and is often the cause of engine noise during startup. Low oil pressure caused by contamination from sludge and other debris of the oil pickup screen also reduces oil pressure to the entire engine. Air in the oil can reduce oil pressure. A low oil level, overfilling the crankcase, or a leak on the suction side of the oil pump, allows oil aeration (foaming), reducing hydraulic pressure. Remember that fluids are not compressible. Air and gases are compressible and result in reduced pressures. Also, do not forget to check the oil filter for restrictions. Oil filter restrictions usually lead to a gradual loss of oil pressure. When the filter is sufficiently restricted, oil bypasses the filter and continues supplying the engine with unfiltered oil still maintaining system pressure. As the media of the filter become more restrictive to flow from debris and sludge, the bypass valve internal to the oil filter opens. When pressure drop (generally 14–20 psi) across the filter media exceeds the opening pressure of the bypass, oil flows around the filter media to the engine, usually without a drop in oil pressure. If the bypass valve fails to open, then damage to the filter results, referred to as “ballooning.” The bypass valve can also open if the oil resists flow. Using the wrong viscosity oil, or oil that is extremely cold and thick, can result in a bypass condition. For example, if oil pressure in the engine is 35 psi it does not mean that there is 35 psi of pressure acting on the bypass valve. If the filter is unrestricted, 35 psi will be present on the inlet and outlet sides of the valve and the filter functions as intended. However, if the pressure on the input side of the valve is 14 to 20 psi higher than the output side due to an internal restriction, the bypass valve opens. Oil weight and condition issues can also cause low oil pressure. The wrong viscosity oil, resulting from adding the incorrect oil weight during an oil change, thinning of the oil that occurs during normal usage, or extended service intervals can reduce oil pressure. Oil viscosity issues arise from leaking fuel injectors or an engine misfire, thinning the oil from fuel dilution. Faulty PCV/crankcase breathing faults or sticking piston rings dilute or contaminate engine oil with hydrocarbons and carbon. Engine sludging from oil contamination and poor maintenance also reduces oil pressure and may require engine replacement to resolve.

Oil Leak Diagnosis Another source of oil loss is from a leak. Inspecting for an oil leak may be part of routine maintenance or part of a diagnostic procedure for a customer complaint about a loss of oil, burning smell, or stains on the driveway. A loss of oil regardless of whether it is a leak or from consumption can cause engine performance issues or engine damage. Fluid leak diagnosis, irrespective of the type, is typically a straightforward approach that may include the use of special tools to locate the source. Leaks can occur from a variety of sources; many may have the same color. Dark fluid leaks may be engine oil, burnt or aged transmission and power steering fluid, or even gear lube from a front transfer case or axle assembly. The technician may be able to locate the source visually, assuming the leak has not existed for an extended time or is not excessive. Using the sense of smell may help isolate the leak to the proper component also. Gear oil and burnt transmission fluid have a very distinctive odor, as do fuel and brake fluid, compared to engine oil. During your inspection, remember that gravity causes fluid to flow downward. Be sure to inspect up to the highest point where the fluid is no longer present. Also be aware that air from cooling fans and driving the vehicle may push the fluid in the direction of the airflow. Oil leaks may also occur due to a fault PCV system. A restriction in the PCV valve or related lines and hoses allows crankcase pressures to build enough pressure to cause oil leaks. These oil leaks often are unusual (see case study), where PCV vapors find a way to vent to atmospheric (lower) pressure. It may be as simple as the oil dipstick being pushed out of its mounting location creating a vent path from the crankcase to a sensor mounted on the engine that is also exposed to the crankcase vapors. A stuck open PCV system allows excessive crankcase vapors to enter the intake system. This can affect fuel trim

and can set a fuel system too lean or too rich DTC depending on how much the vapors are saturated with hydrocarbons (HC). If PCV vapor is low in HC, it may cause the fuel trim to compensate for the unmetered air leak into the engine by increasing fuel trim, setting a P0171 System Too Lean DTC. A crankcase saturated with HC vapor may cause a reduction in fuel trim setting a P0172 System Too Rich DTC.

PCV Case Study A 2007 Suzuki Aerio was towed in for a no-start condition. The technician noted no DTCs and the MIL was OFF. Cranking and watching PID data, the engine rpm data showed 0 rpm. The technician inspected the CKP sensor that had oil leaking from the harness connector at the sensor. The technician replaced the sensor feeling that it was damaged and was allowing oil to leak through its housing. The technician also cleaned the oil residue from the harness and surrounding area. A new sensor was installed and a visual recheck of the area showed all OK. About two weeks later, the vehicle was towed back in. Again, no CKP signal. The technician found an oil-contaminated CKP sensor and harness connector. This time, however, the technician knew the chances of getting a bad part with the same type of fault, an oil leak, was unlikely. The PCV system was checked. The PCV valve was stuck closed. A replacement PCV valve and another CKP sensor were installed. The vehicle was now repaired. This case study is a good lesson for digging a little deeper into the cause of an unusual situation. Oil leaks at gaskets and front and rear engine seals are common. Oil leaking through sensors is not. If oil is leaking past a sensor or other sealing type component exposed to crankcase vapors, be sure to check the PCV system for proper operation. If isolating and locating the source of the leak proves difficult, a technician may use fluorescent dye and a black light, or leak trace powder (FIGURE 12-19). If the leak is excessive or has been occurring for a while, clean and degrease the engine before continuing diagnosis. Fluorescent leak detection is used in oil-based systems, coolant, air conditioning, and fuel systems. The dye is fluorescent, so under a black light (UV light) it produces a distinct yellow-green glow, which is enhanced when using yellow-coated glasses. The dye selected for use may be fluid specific or, due to advances in technology, an all-in-one dye (not fluid specific) is now available. Major U.S. and foreign vehicle manufacturers add leak detection dye to vehicles on the assembly line as part of their quality control programs. The dye added will remain in the system until the fluid has leaked out, been used up, or been changed.

FIGURE 12-19 Oil leak dye added to engine oil can help you identify the source of the leak. © Jones & Bartlett Learning.

Two different types of dyes are available for use. The dye selected determines which light to use. One dye fluoresces best under ultraviolet light, and the other under blue light. All-in-one dyes contain both distinct fluorescent dyes to produce the telltale glow no matter which type of inspection lamp is used. Current dyes are now more visible than earlier versions, allowing the use of smaller, more compact and flexible lamps to intensify the appearance of the dye. After thoroughly cleaning the engine to remove old traces of the leak, add dye to the oil and allow it to circulate for 10 minutes or more. Some manufacturers recommend removing 1 quart of oil from the engine into a container and mixing it with the dye. Place the oil back into the engine and run it to circulate the oil. Shine the light into the area of the suspected leak. Glowing dye indicates the leak. In some cases, the leak may be difficult to reproduce. An extended test drive or returning the vehicle to the customer to drive for several days may be required before retesting. If using an aerosol or leak trace powder such as baby powder or talcum powder, distribute the powder in the suspected leak area. As the powder dries, it turns into an extremely bright white color. Leaking oil becomes highly visible against the white background, isolating the leak area. The powder, which is safe on painted surfaces, vinyl, and rubber, is also useful for finding wind, dust, and water leaks. Foot powder, talcum powder, and baby powder are also used, but application to the engine may prove harder than the aerosol version designed for leak detection.

Coolant Consumption Coolant loss can occur from a leak or by burning it during the combustion process. Unlike oil, for which a small amount of usage is reasonable, an engine should not lose or use any coolant. As with any

diagnosis, begin with a thorough visual inspection. If the visual inspection is unable to pinpoint the source of the leak, perform a pressure test. Fluorescent dye testing is also used to locate external and internal leaks. Symptoms of a cooling system or head gasket failure include: Engine temperature rising above normal or wide-ranging fluctuations of the coolant gauge Coolant loss without signs of an external leak White exhaust smoke Coolant rising in the degas bottle with a brown-tan color Coolant being expelled from the expansion tank Loss of oil with no visible leaks Oil level rising Color of the oil changing or accompanied by a milkish color Modern vehicles with complex multizoned coolant loops and coolant control valves are susceptible to air pockets. Refilling the cooling system without following manufacturer’s procedures or using a vacuumassisted coolant fill tool creates air pockets that result in wide temperature swings and overheating. Overheating, rising coolant levels, and coolant loss from the expansion tank can also arise from a variety of other issues, including a sticking thermostat, a cooling fan fault, or a plugged radiator. As with most engine concerns, a full list of possibilities for a problem exists, enforcing the premise of a thorough, complete diagnosis. Pressure testing the cooling system either follows or is included while performing a visual inspection. The cooling system pressure tester can be either a hand pump or air assisted. A technician applies pressure to the cooling system with the tool (FIGURE 12-20). Coolant leaks can occur during either lowpressure or high-pressure conditions; checking at both pressures is sometimes required to find a leak. The maximum pressure applied should not exceed system pressure. To test the radiator or expansion tank cap for a leak, use the proper adapter and the pressure tester.

FIGURE 12-20 Cooling system pressure testing can help locate the coolant leak source. © Jones & Bartlett Learning.

Use caution when pressure testing a vehicle with hot coolant. Never remove the radiator cap from an engine that has been operating even for a short time, as the coolant can burn you. Allowing the engine to cool reduces system pressure and thus prevents fluid or steam burns. Verify that the cooling system is full. Install the pressure tester and apply approximately 10 pounds of pressure. Many modern vehicles will require an adapter for connecting the tool to the vehicle. Allow the vehicle to sit with pressure applied for 20 to 30 minutes and monitor the gauge for a pressure loss. If the pressure drops, inspect for leaks. If a leak is not found, increase the pressure. Do not exceed maximum system pressure (generally 13 to 16 psi on modern vehicles). This specification is available in service information or on the radiator cap itself. Again, allow the vehicle to sit for the allotted time monitoring the gauge pressure. Common problem areas for leaks include all hoses, radiator, water pump, cylinder heads, and heater core.

Coolant Dye Testing Similar to oil dye testing, coolant leaks are also checked using dye and a black light. Dye testing a coolant system is useful in finding internal and external coolant leaks. Dye testing either replaces or at times becomes an additional diagnostic test for hard-to-find leaks. On difficult-to-duplicate or very slow leaks the customer may need to drive the vehicle for several days before the dye will produce the source of the leak. To find a leak, add the dye to the coolant and circulate it, allowing the engine to reach operating temperature. Remember to allow the engine to cool before removing the radiator or expansion tank cap. Use the black light to trace the source. For internal coolant consumption, remove the spark plugs and check for the telltale fluorescent green-yellow dye color on the body or electrodes (FIGURE 12-21). For

difficult-to-find internal leaks, pressure testing the cooling system after operating the engine through several hot and cold cycles may produce the leak. Allow the engine to sit overnight with pressure applied, then check the spark plugs for dye the following day. Dye appearing on the spark plug indicates coolant is leaking into the cylinder. Depending on the severity of the coolant usage, a misfire code for a particular cylinder may be present indicating which cylinder(s) to check first.

FIGURE 12-21 Cooling system dye can help locate a leak that is hard to determine. Today’s vehicles have more packed into a smaller package, which makes diagnosing them more difficult. © Jones & Bartlett Learning.

Diagnosing Head Gasket Failure and Coolant Loss without Visible Leaks 12-6 Analyze the integrity of the cylinder head gasket.

The head gasket is responsible for sealing combustion pressure inside the combustion chamber. Failure of a head gasket, therefore, is a critical fault. A head gasket failure can cause multiple symptoms. These symptoms can also be caused by defects other than a head gasket failure, complicating the diagnosis. Symptoms of head gasket failure are dependent on how it fails. The term “blown head gasket” used to be all inclusive of any head gasket failure regardless of how it failed. Repeated overheating, excessive steam from the exhaust, an engine misfire, loss of coolant without any external leaks, an oily residue found in the coolant overflow/degas bottle, and coolant in the engine oil are just a few of the possibilities. Complicating diagnosis is that other faults can mimic or cause a head gasket failure. Multiple failures can also occur, resulting in more than one symptom. A restricted radiator or electric cooling fan that is either inoperative, missing a speed, or does not come on at the right temperature, leading to overheating, acts similar to a head gasket failure. On some V-type engine designs, a leaking intake manifold gasket can cause coolant in the oil, which is often misdiagnosed as a head gasket failure (FIGURE 12-22).

FIGURE 12-22 Leaking intake gaskets can be potentially the cause of an overheating problem, as when the coolant gets low in the engine it can cause issues with gaskets and warpage. © Jones & Bartlett Learning.

Head gasket failures often are the result of the engine overheating—a consequence of a coolant leak somewhere else in the cooling system that is left unrepaired. Additional faults included a thermostat that fails to open correctly or an electric cooling fan failure. When the engine overheats, thermal expansion beyond the system design occurs, resulting in a failed head gasket, a warped or cracked head, or an engine block head surface. When a cylinder head gets too hot, it can expand and crush the head gasket. The failure typically appears at the thinnest part of the head gasket, between the cylinders. This damage allows combustion pressure and allows coolant to leak. If coolant enters the exhaust from the combustion chamber, damage to other engine components can occur. Coolant can mix with the oil or oil can mix with the coolant (FIGURE 12-23). Coolant mixing with the engine’s oil reduces its lubrication abilities. The coolant alters the oil’s viscosity, causing enginebearing damage. Coolant and oil mixing may produce a visible milky appearance. However, unlike pure water, glycol may not turn the oil milky. In a difficult diagnostic situation, or for warranty approval, take an engine oil sample and send it to an oil-testing lab to verify the presence of glycol.

FIGURE 12-23 When coolant and oil mix, the appearance can be similar to a milkshake. This mixing can also cause the failure of hoses or anything else that it touches. © Jones & Bartlett Learning.

TECHNICIAN TIP Use caution when testing for a blown head gasket. An engine with a head gasket fault or cracked cylinder head/block can build excessive pressure and overheat quickly. Boiling, pressurized coolant can cause components to rupture or be expelled violently when removing the radiator cap or testing with the cap already off.

Failed Head Gasket Diagnosis Always begin any diagnostic sequence with the least intrusive, easiest to perform testing, before timeconsuming testing or disassembly of components. A failed head gasket is no different. Check for cylinder misfire codes by scanning the PCM. Perform a power balance test to find any weak cylinders. If the power balance test identifies a weak cylinder or a code is present, pay particular attention to the cylinder(s) during testing. The simplest check is visual; look for oil contamination and excessive steam from the exhaust. Excessive steam from the exhaust that continues after the engine has reached operating temperature indicates a possible head gasket or cylinder head fault. Check the oil. Remove the dipstick and oil fill cap and inspect for a milky residue. If a creamy tan or off-white color is present, it is a good indication that coolant is entering the engine oil. Coolant can enter the oil due to a failed head gasket from a cracked or warped cylinder head or engine block surface. An oily residue in the coolant or found in the expansion/degas bottle is another quick visual indicator. An absence of a milky residue does not indicate that a blown head gasket does not exist. Remember that ethylene glycol, unlike water, will not always produce a milky white residue. If finding a milky residue, additional testing is required to verify that a failed head gasket is at fault. A milky white residue can also be present from an incorrectly operating PCV system or fixed orifice system. A failed oil-to-coolant heat exchanger is another way for coolant and oil to mix. Regular short trips also cause the oil to have a milky appearance. Repeated short trips prevent the engine from reaching operating temperature, hampering the burning of normal condensation during vehicle operation. A similar test uses a coolant pressure tester on a hot engine. Warm the engine to operating temperature and disable the fuel system, preventing raw fuel from spraying into the cylinders. Safely remove the radiator cap from the hot engine and install the coolant pressure tester. Pressurize the cooling system to the maximum system level as found in service information or on the radiator cap. Remove the spark plugs and inspect for signs of coolant on the insulator or electrodes. Crank the engine over again, this time with pressure applied. Look for coolant spraying from the spark plug holes. If the coolant is not visible during either test when cranking the engine, use a borescope in the spark plug holes to inspect for coolant or visible cracks in the cylinder walls. A failed head gasket can pass all the abovementioned tests. Head gaskets can fail without inducing combustion gases and pressure into the coolant or causing coolant to mix with the oil. Two adjacent cylinders missing is a good indication of a failed head gasket or a warped or cracked cylinder head. A recess in the gasket allows the compression of the two cylinders to leak into each other. Perform a compression test or power balance to confirm. If compression is low in both cylinders, remove the cylinder head and inspect for a failed gasket or the cylinder head being cracked or warped.

Combustion Leak Detector An overheating engine caused by a low coolant level can be from an external or internal leak. If a visible leak is not detected using fluorescent dye, or by pressure testing, suspect an internal leak. Coolant flowing into the combustion chamber combines with the air-fuel mixture and burns as part of the combustion process. Depending on how much coolant is present in the cylinder, white smoke or steam may be seen from the exhaust, accompanied by a sweet smell of the coolant burning. If the internal leak is relatively small, steam may or may not be visible. If coolant can leak into the cooling system, then combustion can leak into the cooling system. This test checks for combustion in the cooling system. SKILL DRILL 12-2 Detecting a Combustion Leak

1. Verify the coolant level is low enough (2 to 3 inches below the full level) to prevent coolant from entering the tube and test fluid.

2. Remove the top of the tester and add testing fluid to the fill line on the tester tube.

3. Place the tester over the opening with a light twist to form a seal with the radiator or degas bottle.

4. Run the engine to 2500 rpm. Loading the engine by power braking will help increase cylinder pressures.

5. With the engine running, squeeze the bulb at the top of the tester continually for about 1 minute, to draw air from the cooling system through the tester and test fluid.

6. If a leak is present, the blue fluid will turn yellow, indicating combustion gases in the cooling system. © Jones & Bartlett Learning

Another method for finding an internal leak is the chemical combustion leak detector. The chemical leak test verifies a combustion leak into the cooling system using a blue special test fluid, a clear sight glass, and a squeeze bulb (FIGURE 12-24). The test fluid changes colors when exposed to carbon dioxide. The chemical leak test is the least intrusive way to find a leak. To perform combustion leak detection, follow the steps in SKILL DRILL 12-2.

FIGURE 12-24 Using a block tester will draw combustion fumes from the cooling system into the tester that will verify that the head gasket or cylinder head has a leak from the combustion chamber. © Jones & Bartlett Learning.

TECHNICIAN TIP If coolant enters the tester, the fluid is contaminated and will have to be discarded and the test rerun.

Using an Exhaust Gas Analyzer to Find a Faulty Head Gasket If available, use an exhaust gas analyzer to detect combustion gases in the cooling system. Similar to the chemical liquid test, the exhaust analyzer detects combustion gases in the cooling system. To perform the test, remove the radiator or expansion tank cap. Run the engine at 2500 rpm for 2 minutes, then return to idle. With the engine running, place the exhaust probe above the radiator or expansion tank. Use caution to prevent the probe from drawing in coolant during this test. Some coolant may need to be drained to prevent contaminating the exhaust probe with coolant. Keep the coolant level 2 to 3 inches below where placing the probe. Allowing coolant to enter the exhaust probe will damage it. Monitor the exhaust gas analyzer for a significant increase in hydrocarbons (HC) (unburned fuel) and carbon monoxide (CO) (partially burned fuel). An increase in either gas proves combustion gases are entering the cooling system. If the readings do not increase, test again, this time while holding the engine speed at 2500 rpm.

WRAP-UP Ready for Review Engine noises can direct the technician to the proper engine area for diagnosis. Valve train noises can be caused by small clearances created by wear in the valve train. Timing chain noise can be caused by worn guides, stretched chains, or failed tensioners. Preignition and detonation are different issues. Oil consumption testing should be conducted to determine whether the engine is burning oil. Verifying oil pressure is recommended when diagnosing a VVT issue. Leaking head gaskets can cause an overheating condition. Diagnosing leaking head gaskets can be done using a block tester. An exhaust gas analyzer can help determine whether there is a head gasket leak. Coolant consumption should be monitored when diagnosing a misfire. High-tech engine mounts allow for the mount to become adjustable to compensate for noises. Standard motor mounts are major sources of vibrations on the engine. A cracked flexplate/flywheel can cause a noise at the rear of the engine.

Key Terms Active motor mounts Engine mounts that change in relation to engine operation to stop stray vibrations depending on the operational situation. Automotive stethoscope Tool that includes a long, solid metal probe at the end that, when held against a solid component, transfers sound to the earpieces. Decoupler pulleys High-tech pulleys that provide belt-drive power to the alternator during acceleration and cruising speeds. Detonation The reaction when the spark plug ignites the air-fuel, as it should; however, the flame front initiated by the spark plug collides with an undesired flame front. Front-end accessory drive (FEAD) component A front-end accessory drive component is anything that is driven off the front of the engine. Noise, vibration, and harshness (NVH) Automotive vibrations and harsh operations that need to be diagnosed as a customer concern. One-way clutch (OWC) pulley A clutch on an alternator that drives only one way and slips the opposite way. Overrunning alternator decoupler (OAD) This decouples the alternator to eliminate it as a source of vibration when it is not needed. Wire tachometer An inexpensive tool used to determine the rpm at which a noise or vibration is occurring. A wire is used to monitor the vibration, and the tool indicates the rpm.

Review Questions 1. Internal engine noises are usually diagnosed first when an engine performance issue is also documented on the repair order for which of the following? a. Internal engine components can cause performance issues. b. Internal engine components are easier to fix. c. Mechanical issues are more important. d. They are easier to deal with. 2. All of the following statements with respect to head gasket leakage are true EXCEPT: a. A leaking head gasket can use all the coolant in the vehicle. b. A leaking head gasket can increase compression. c. Head gaskets seal the cylinder block to the cylinder head. d. Overheating the engine can cause the head gasket to blow. 3. Low or no oil pressure in an engine may cause which of the following? a. Ignition timing issues b. Damage to engine components c. Fuel injector failure d. PCM failure 4. Engine noise that occurs every other crankshaft revolution may be related to which of the following? a. A main bearing failure b. A damaged crankshaft damper and pulley assembly c. A valve train–related failure d. A failed A/C compressor clutch bearing 5. Oil consumption can cause engine performance issues because of the oil film that is coating the spark plug. This can create the NVH issue caused by which of the following? a. Cylinder misfire b. Noisy valve guides c. Ignition coil failure d. Valve float at normal engine rpm 6. Valve train clearance can cause a running issue for which of the following reasons? a. Valve train clearance does not cause a running issue. b. Increased fuel injector on-time c. Valve train clearance can change the operation of camshaft. d. Misadjusted valves can create an engine misfire condition. 7. A warped cylinder head can cause all of the following issues EXCEPT: a. an overheating issue. b. a running issue that may show up as a misfire. c. a warped cylinder head that may cause a fuel injection leak. d. a warped cylinder head that may cause a coolant leak. 8. A timing chain that has been stretched should: a. be replaced with a new chain, guides, and sprockets. b. be reinstalled in the opposite direction so that it can be reused. c. be monitored once the engine is put back into service. d. have the master link replaced to restore tension. 9. When the head gasket is leaking exhaust into the cooling system, diagnosing it can be accomplished by which of the following? a. Using a scan tool to determine which cylinder is leaking exhaust into the coolant

b. Using a block tester to detect exhaust fumes in the coolant c. Disassembling the cooling system d. Replacing the thermostat 10. With later model engines having ECM controlled motor mounts, there may be a circuit fault in which of the following? a. The solenoid that controls the mount b. The crankshaft position sensor c. A VVT control solenoid d. The starter solenoid

ASE Technician A/Technician B Style Questions 1. Technician A says that a standard engine mount can mechanically fail and cause a vibration. Technician B says that an electronically controlled engine mount will not cause a vibration or noise concern because it can adapt to failures. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B 2. Technician A says that preignition situations can cause internal engine component failures. Technician B says that a timing chain that has been stretched can cause a noise and an engine performance issue. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B 3. Technician A says that engine oil consumption is never related to an NVH concern. Technician B says that some coolant consumption is normal in an engine. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B 4. Technician A says that incorrect valve train clearance can cause top-end engine noise. Technician B says that bottom-end noise usually accompanies internal engine failure. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B 5. Technician A says that a failed head gasket can cause a misfire to be created within the engine. Technician B says that a failed head gasket cannot be determined exclusively by a scan tool. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B 6. Technician A says that an oil-fouled spark plug usually indicates a failed head gasket. Technician B says that a gas analyzer can be used to verify a head gasket leak. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B 7. Technician A says that unstable oil pressure can cause VVT-related noise concerns. Technician B says that a detonation condition can cause the PCM to advance the timing to try and correct the condition. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B

8. Technician A says that a normal fuel injector makes the same amount of noise that a GDI injector makes. Technician B says that front-end accessory noise could be the result of a faulty alternator bearing. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B 9. Technician A says that there are oil consumption test conditions that must be performed by the technician. Technician B says that a cracked flexplate/flywheel can cause an engine noise that could be misdiagnosed as an engine misfire. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B 10. Technician A says that burning coolant in the combustion chamber can cause the catalyst to become damaged. Technician B says that engine oil pressure is essential for proper engine operation. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B

© Jones & Bartlett Learning.

Appendix A 2017 ASE Education Foundation Automobile Accreditation Task List Correlation Guide

© Jones & Bartlett Learning.

Appendix B Preparing for the ASE Advanced Engine Performance Specialist Test (L1) L1 Test Overview The ASE A8 Engine Performance certification test centers around measuring knowledge of engine performance systems, components, and diagnostic testing. The L1 Advanced Engine Performance certification test builds on the technician’s knowledge with a focus on the higher-order skill set of analyzing data along with related reference information to determine the most likely cause of an engine performance customer concern.

Studying for the L1 Test Preparing to take and pass the L1 test requires first that the technician has passed the A8 test. The A8 test is a prerequisite to register for the L1 test. The A8 test is centered around engine performance knowledge. For example, the test questions are designed to determine whether you can select the correct answer for the role of the oxygen sensor or air-fuel ratio sensor with respect to the engine control system. SAMPLE QUESTION Technician A says that the air-fuel ratio sensor operates immediately at engine start and provides data to the PCM to increase injector on-time at cold start. Technician B says that the oxygen sensor generates a high voltage signal of about 900 mV to indicate a lean mixture.

Who is correct? The answer for this question is that neither technician is correct. This question verifies that a technician knows that an oxygen or air-fuel ratio sensor must heat up to operating temperature before providing data to the PCM to control injector ontime. It also verifies whether the technician knows that an oxygen sensor generates a high voltage signal in response to a rich condition, not a lean condition. The A8 questions focus on the knowledge a technician must have to describe how a component functions or how a mechanical issue, such as low compression in a cylinder, affects overall engine performance.

The L1 test builds on your engine performance knowledge, which is why you must pass A8 before you can register for L1. The L1 test is an application of your engine performance knowledge. The test requires use of a “Composite Vehicle Reference Booklet.” This reference provides the details of a particular vehicle that is the basis for the questions in the test. It is important that you obtain the most current composite vehicle booklet when studying for the L1 test. Note that you do not need to memorize what is in the booklet; rather, you should familiarize yourself with the components and systems outlined in it. You can use the reference booklet during the L1 test, as a copy will be provided for you at the test center. (You cannot use one that you printed or obtained from ASE, as you may have made notes in it,

and those are not allowed to be used when taking the test.) For example, if you are unfamiliar with variable valve lift systems, then you should not only review the type of system described in the composite vehicle booklet, but also study references from a course textbook or articles on the various systems that can be found in technician repair publications, study guides, and textbooks. The goal from your study time is to enter the ASE test center fully understanding how the systems and components described in the composite vehicle reference operate and any related test procedures. The L1 test questions often present scenarios based around data from the scan tool, digital multimeter (DMM), graphing multimeter, and digital storage oscilloscope (DSO) screen captures. For example, see FIGURE B-1.

FIGURE B-1 This is an example of scan tool data provided in the L1 test.

Description SAMPLE QUESTION A vehicle is towed in for a crank no-start condition. The technician checks for DTCs and none are stored. The technician records the data shown during engine cranking. Technician A says that the data indicate the CKP sensor and related circuit may be the cause. Technician B says that the data indicate that the desired idle speed is too high for starting conditions and may be the cause.

Who is correct? For this question, technician A is correct. Now this one is relatively easy, since the 0 RPM data is easy to spot. Most of the questions will require that you refer to the composite reference booklet to interpret various sensor data values for a given condition and then determine whether they are within normal range or out of range. This is why you must fully understand the systems and the components, as well as be familiar with them as detailed in the reference booklet as part of your study time. If you do not study, you will end up doing your studying during the test and you will take too long to answer the questions, running out of time to complete the test. The test will also cover DTC diagnostics and no-DTC diagnostic situations. These questions often use test data that you must interpret. For example, see FIGURE B-2.

FIGURE B-2 The L1 test often includes component wiring diagrams for inputs and outputs, along with related voltage readings called out.

Description SAMPLE QUESTION A vehicle is in for a customer concern of poor fuel economy and hard starting when the engine is warm. The technician is measuring 4.1 V at ECT pin 2 (arrow) with the engine at 180° F, measured with an infrared thermometer. The scan tool shows the engine temperature is 23° F. What could be the cause of this concern? A. B. C. D.

Open ECT sensor thermistor Shorted ECT sensor thermistor High resistance on the ground side of the ECT circuit An open between the PCM and ECT Pin 2

This question requires that you understand the operation of the ECT sensor and circuit, and that you can interpret readings from a DMM, infrared thermometer, and scan tool PID data. The correct answer is C. High resistance in the wiring between the ECT and ground could create this condition. The extra resistance adds to the resistance of the ECT thermistor, and the PCM interprets the 4.1 V as a cold engine, as indicated by the PID data. A voltage drop test of the wire between the ECT pin 1 and the PCM ground circuit could validate whether this is in fact the fault. The other answers would not provide a DMM reading of 4.1 V or the scan tool data. An open ECT sensor would have 5 V at pin 2 and would set a DTC. A shorted sensor would have 0 V at pin 2 and would set a DTC. An open between ECT pin 2 and the PCM would result in a DMM reading of 0 V and scan tool data indicating a very cold temperature, such as −40° F, along with setting a DTC.

L1 Emission Test–Related Questions The L1 test also includes several questions on emission testing. These questions usually show emission test results from a vehicle that has failed for excessive NOx, CO, or HC. You must be able to interpret the test results for two-speed idle and loaded mode test procedures. Prepare for these questions by reviewing the Emissions Testing content in this text. Make sure you understand the various conditions that can cause high levels of these emissions. For example, see FIGURE B-3.

FIGURE B-3 Emissions test readings are presented for your interpretation as to the cause of the condition.

Description SAMPLE QUESTION A vehicle has failed a loaded mode emission test for high levels of HC. What could be the cause of high HC levels for this vehicle? A. B. C. D.

Valve adjustment too tight on one or more valves Continuous misfire of one or more cylinders Leaking injector in one cylinder EGR valve stuck closed

The correct answer is A. The EGR being stuck closed would increase NOx emissions, not HC emissions. A leaking fuel injector would create issues for both loaded mode test speeds, and only the 25mph speed has the very high HC levels. A misfire would have very low levels of CO and NOx at both test speeds, as these are byproducts of combustion; however, the test readings show NOx and CO are present. The CO NOx levels are very low at the 25-mph portion of the test, indicating that there may be a partial misfire, possibly due to one or more valves being out of adjustment. Valve clearance that is too tight, not enough clearance, can keep the valve from fully seating, causing incomplete or no fuel burn on the power stroke. This would increase HC levels and reduce CO and NOx levels. From this type of question, it is understandable that many emission inspection licensing bodies include the L1 test as part of their requirements to apply for a license before taking their related emission licensing exam. The L1 test is not difficult if you ensure you are ready. Have you had enough experience diagnosing engine performance concerns? Are you familiar with engine performance systems and related component operation? Are you able to interpret DMM, scan tool, and DSO data? Are you familiar with emission testing and inspection procedures and vehicle failure diagnosis? Are you ready to put in the time to study the L1 test study guide and composite reference booklet? If you answered yes to all these questions, then you are ready. Visit the ASE site (www.ase.com) and download the L1 test information. Putting in the effort and time should ensure that you pass this important industry certification test.

© Jones & Bartlett Learning.

Appendix C Generic OBD II Codes Present on All OBD II Vehicles P0000

No trouble code

P0001

Fuel Volume Regulator Control Circuit/Open

P0002

Fuel Volume Regulator Control Circuit Range/Performance

P0003

Fuel Volume Regulator Control Circuit Low

P0004

Fuel Volume Regulator Control Circuit High

P0005

Fuel Shutoff Valve Control Circuit/Open

P0006

Fuel Shutoff Valve Control Circuit Low

P0007

Fuel Shutoff Valve Control Circuit High

P0008

Engine Position System Performance—Bank 1

P0009

Engine Position System Performance—Bank 1

P0010

Intake Camshaft Position Actuator Circuit/Open (Bank 1)

P0011

Intake Camshaft Position Timing—Over-Advanced (Bank 1)

P0012

Intake Camshaft Position Timing—Over-Retarded (Bank 1)

P0013

Exhaust Camshaft Position Actuator Circuit/Open (Bank 1)

P0014

Exhaust Camshaft Position Timing—Over-Advanced (Bank 1)

P0015

Exhaust Camshaft Position Timing—Over-Retarded (Bank 1)

P0016

Crankshaft Position Camshaft Position Correlation Bank 1 Sensor A

P0017

Crankshaft Position Camshaft Position Correlation Bank 1 Sensor B

P0018

Crankshaft Position Camshaft Position Correlation Bank 2 Sensor A

P0019

Crankshaft Position Camshaft Position Correlation Bank 2 Sensor B

P0020

Intake Camshaft Position Actuator Circuit/Open (Bank 2)

P0021

Intake Camshaft Position Timing—Over-Advanced (Bank 2)

P0022

Intake Camshaft Position Timing—Over-Retarded (Bank 2)

P0023

Exhaust Camshaft Position Actuator Circuit/Open (Bank 2)

P0024

Exhaust Camshaft Position Timing—Over-Advanced (Bank 2)

P0025

Exhaust Camshaft Position Timing—Over-Retarded (Bank 2)

P0026

Intake Valve Control Solenoid Circuit Range/Performance (Bank 2)

P0027

Exhaust Valve Control Solenoid Circuit Range/Performance (Bank 2)

P0028

Intake Valve Control Solenoid Circuit Range/Performance (Bank 2)

P0029

Exhaust Valve Control Solenoid Circuit Range/Performance (Bank 2)

P0030

Heated Oxygen Sensor (HO2S) Heater Control Circuit Bank 1 Sensor 1

P0031

Heated Oxygen Sensor (HO2S) Heater Circuit Low Voltage Bank 1 Sensor 1

P0032

Heated Oxygen Sensor (HO2S) Heater Circuit High Voltage Bank 1 Sensor 1

P0033

Turbo/Super Charger Bypass Valve Control Circuit/Open

P0034

Turbo/Super Charger Bypass Valve Control Circuit Low

P0035

Turbo/Super Charger Bypass Valve Control Circuit High

P0036

Heated Oxygen Sensor (HO2S) Heater Control Circuit Bank 1 Sensor 2

P0037

Heated Oxygen Sensor (HO2S) Heater Circuit Low Voltage Bank 1 Sensor 2

P0038

Heated Oxygen Sensor (HO2S) Heater Circuit High Voltage Bank 1 Sensor 2

P0039

Turbo/Super Charger Bypass Valve Control Circuit Range/Performance

P0040

Oxygen Sensor Signals Swapped Bank 1 Sensor 1/Bank 2 Sensor 1

P0041

Oxygen Sensor Signals Swapped Bank 1 Sensor 2/Bank 2 Sensor 2

P0042

HO2S Heater Control Circuit (Bank 1, Sensor 3)

P0043

HO2S Heater Control Circuit Low (Bank 1, Sensor 3)

P0044

HO2S Heater Control Circuit High (Bank 1, Sensor 3)

P0046

Turbocharger/Supercharger Boost Control A Circuit Range/Performance

P0047

Turbocharger/Supercharger Boost Control A Circuit Low

P0048

Turbocharger/Supercharger Boost Control A Circuit High

P0049

Turbocharger/Supercharger Turbine Overspeed

P0050

Heated Oxygen Sensor (HO2S) Heater Circuit Bank 2 Sensor 1

P0051

Heated Oxygen Sensor (HO2S) Heater Circuit Low Voltage Bank 2 Sensor 1

P0052

Heated Oxygen Sensor (HO2S) Heater Circuit High Voltage Bank 2 Sensor 1

P0053

HO2S Heater Resistance Bank 1 Sensor 1 (PCM)

P0054

HO2S Heater Resistance Bank 1 Sensor 2 (PCM)

P0055

HO2S Heater Resistance Bank 1 Sensor 3 (PCM)

P0056

Heated Oxygen Sensor (HO2S) Heater Circuit Bank 2 Sensor 2

P0057

Heated Oxygen Sensor (HO2S) Heater Circuit Low Voltage Bank 2 Sensor 2

P0058

Heated Oxygen Sensor (HO2S) Heater Circuit High Voltage Bank 2 Sensor 2

P0059

HO2S Heater Resistance (Bank 2, Sensor 1)

P0060

HO2S Heater Resistance (Bank 2, Sensor 2)

P0061

HO2S Heater Resistance (Bank 2, Sensor 3)

P0062

HO2S Heater Control Circuit (Bank 2, Sensor 3)

P0063

HO2S Heater Control Circuit Low (Bank 2, Sensor 3)

P0064

HO2S Heater Control Circuit High (Bank 2, Sensor 3)

P0065

Air Assisted Injector Control Range/Performance

P0066

Air Assisted Injector Control Circuit or Circuit Low

P0067

Air Assisted Injector Control Circuit High

P0068

MAP/MAF—Throttle Position Correlation

P0069

MAP—Barometric Pressure Correlation

P0070

Ambient Air Temperature Sensor Circuit

P0071

Ambient Air Temperature Sensor Range/Performance

P0072

Ambient Air Temperature Sensor Circuit Low Input

P0073

Ambient Air Temperature Sensor Circuit High Input

P0074

Ambient Air Temperature Sensor Circuit Intermittent/Erratic

P0075

Intake Valve Control Circuit (Bank 2)

P0076

Intake Valve Control Circuit Low (Bank 2)

P0077

Intake Valve Control Circuit High (Bank 2)

P0078

Exhaust Valve Control Circuit (Bank 2)

P0079

Exhaust Valve Control Circuit Low (Bank 2)

P0080

Exhaust Valve Control Circuit High (Bank 2)

P0081

Intake Valve Control Circuit (Bank 2)

P0082

Intake Valve Control Circuit Low (Bank 2)

P0083

Intake Valve Control Circuit High (Bank 2)

P0084

Exhaust Valve Control Circuit (Bank 2)

P0085

Exhaust Valve Control Circuit Low (Bank 2)

P0086

Exhaust Valve Control Circuit High (Bank 2)

P0087

Fuel Rail/System Pressure—Too Low

P0088

Fuel Rail/System Pressure—Too High

P0089

Fuel Pressure Regulator Performance

P0090

Fuel Pressure Regulator Control Circuit

P0091

Fuel Pressure Regulator Control Circuit Low

P0092

Fuel Pressure Regulator Control Circuit High

P0093

Fuel System Leak Detected—Large Leak

P0094

Fuel System Leak Detected—Small Leak

P0095

Intake Air Temperature Sensor 2 Circuit

P0096

Intake Air Temperature Sensor 2 Circuit Range/Performance

P0097

Intake Air Temperature Sensor 2 Circuit Low Input

P0098

Intake Air Temperature Sensor 2 Circuit High Input

P0099

Intake Air Temperature Sensor 2 Circuit Intermittent/Erratic

P0100

Mass or Volume Air Flow Circuit Malfunction

P0101

Mass or Volume Air Flow Circuit Range/Performance Problem

P0102

Mass or Volume Air Flow Circuit Low Input

P0103

Mass or Volume Air Flow Circuit High Input

P0104

Mass or Volume Air Flow Circuit Intermittent

P0105

Manifold Absolute Pressure/Barometric Pressure Circuit Malfunction

P0106

Manifold Absolute Pressure/Barometric Pressure Circuit Range/Performance Problem

P0107

Manifold Absolute Pressure/Barometric Pressure Circuit Low Input

P0108

Manifold Absolute Pressure/Barometric Pressure Circuit High Input

P0109

Manifold Absolute Pressure/Barometric Pressure Circuit Intermittent

P0110

Intake Air Temperature Circuit Malfunction

P0111

Intake Air Temperature Circuit Range/Performance Problem

P0112

Intake Air Temperature Circuit Low Input

P0113

Intake Air Temperature Circuit High Input

P0114

Intake Air Temperature Circuit Intermittent

P0115

Engine Coolant Temperature Circuit Malfunction

P0116

Engine Coolant Temperature Circuit Range/Performance Problem

P0117

Engine Coolant Temperature Circuit Low Input

P0118

Engine Coolant Temperature Circuit High Input

P0119

Engine Coolant Temperature Circuit Intermittent

P0120

Throttle Pedal Position Sensor/Switch A Circuit Malfunction

P0121

Throttle/Pedal Position Sensor/Switch A Circuit Range/Performance Problem

P0122

Throttle/Pedal Position Sensor/Switch A Circuit Low Input

P0123

Throttle/Pedal Position Sensor/Switch A Circuit High Input

P0124

Throttle/Pedal Position Sensor/Switch A Circuit Intermittent

P0125

Insufficient Coolant Temperature for Closed Loop Fuel Control

P0126

Insufficient Coolant Temperature for Stable Operation

P0127

Intake Air Temperature Too High

P0128

Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature)

P0129

Barometric Pressure Too Low

P0130

O2 Sensor Circuit Malfunction (Bank 1 Sensor 1)

P0131

O2 Sensor Circuit Low Voltage (Bank 1 Sensor 1)

P0132

O2 Sensor Circuit High Voltage (Bank 1 Sensor 1)

P0133

O2 Sensor Circuit Slow Response (Bank 1 Sensor 1)

P0134

O2 Sensor Circuit No Activity Detected (Bank 1 Sensor 1)

P0135

O2 Sensor Heater Circuit Malfunction (Bank 1 Sensor 1)

P0136

O2 Sensor Circuit Malfunction (Bank 1 Sensor 2)

P0137

O2 Sensor Circuit Low Voltage (Bank 1 Sensor 2)

P0138

O2 Sensor Circuit High Voltage (Bank 1 Sensor 2)

P0139

O2 Sensor Circuit Slow Response (Bank 1 Sensor 2)

P0140

O2 Sensor Circuit No Activity Detected (Bank 1 Sensor 2)

P0141

O2 Sensor Heater Circuit Malfunction (Bank 1 Sensor 2)

P0142

O2 Sensor Circuit Malfunction (Bank 1 Sensor 3)

P0143

O2 Sensor Circuit Low Voltage (Bank 1 Sensor 3)

P0144

O2 Sensor Circuit High Voltage (Bank 1 Sensor 3)

P0145

O2 Sensor Circuit Slow Response (Bank 1 Sensor 3)

P0146

O2 Sensor Circuit No Activity Detected (Bank 1 Sensor 3)

P0147

O2 Sensor Heater Circuit Malfunction (Bank 1 Sensor 3)

P0148

Fuel Delivery Error

P0149

Fuel Timing Error

P0150

O2 Sensor Circuit Malfunction (Bank 2 Sensor 1)

P0151

O2 Sensor Circuit Low Voltage (Bank 2 Sensor 1)

P0152

O2 Sensor Circuit High Voltage (Bank 2 Sensor 1)

P0153

O2 Sensor Circuit Slow Response (Bank 2 Sensor 1)

P0154

O2 Sensor Circuit No Activity Detected (Bank 2 Sensor 1)

P0155

O2 Sensor Heater Circuit Malfunction (Bank 2 Sensor 1)

P0156

O2 Sensor Circuit Malfunction (Bank 2 Sensor 2)

P0157

O2 Sensor Circuit Low Voltage (Bank 2 Sensor 2)

P0158

O2 Sensor Circuit High Voltage (Bank 2 Sensor 2)

P0159

O2 Sensor Circuit Slow Response (Bank 2 Sensor 2)

P0160

O2 Sensor Circuit No Activity Detected (Bank 2 Sensor 2)

P0161

O2 Sensor Heater Circuit Malfunction (Bank 2 Sensor 2)

P0162

O2 Sensor Circuit Malfunction (Bank 2 Sensor 3)

P0163

O2 Sensor Circuit Low Voltage (Bank 2 Sensor 3)

P0164

O2 Sensor Circuit High Voltage (Bank 2 Sensor 3)

P0165

O2 Sensor Circuit Slow Response (Bank 2 Sensor 3)

P0166

O2 Sensor Circuit No Activity Detected (Bank 2 Sensor 3)

P0167

O2 Sensor Heater Circuit Malfunction (Bank 2 Sensor 3)

P0168

Engine Fuel Temperature Too High

P0169

Incorrect Fuel Composition

P0170

Fuel Trim Malfunction (Bank 1)

P0171

System Too Lean (Bank 1)

P0172

System Too Rich (Bank 1)

P0173

Fuel Trim Malfunction (Bank 2)

P0174

System Too Lean (Bank 2)

P0175

System Too Rich (Bank 2)

P0176

Fuel Composition Sensor Circuit Malfunction

P0177

Fuel Composition Sensor Circuit Range/Performance

P0178

Fuel Composition Sensor Circuit Low Input

P0179

Fuel Composition Sensor Circuit High Input

P0180

Fuel Temperature Sensor A Circuit Malfunction

P0181

Fuel Temperature Sensor A Circuit Performance

P0182

Fuel Temperature Sensor A Circuit Low Input

P0183

Fuel Temperature Sensor A Circuit Intermittent

P0184

Fuel Temperature Sensor A Circuit Intermittent

P0185

Fuel Temperature Sensor B Circuit Malfunction

P0186

Fuel Temperature Sensor B Circuit Range/Performance

P0187

Fuel Temperature Sensor B Circuit Low Input

P0188

Fuel Temperature Sensor B Circuit High Input

P0189

Fuel Temperature Sensor B Circuit Intermittent

P0190

Fuel Rail Pressure Sensor Circuit Malfunction

P0191

Fuel Rail Pressure Sensor Circuit Range/Performance

P0192

Fuel Rail Pressure Sensor Circuit Low Input

P0193

Fuel Rail Pressure Sensor Circuit High Input

P0194

Fuel Rail Pressure Sensor Circuit Intermittent

P0195

Engine Oil Temperature Sensor Malfunction

P0196

Engine Oil Temperature Sensor Range/Performance

P0197

Engine Oil Temperature Sensor Low

P0198

Engine Oil Temperature Sensor High

P0199

Engine Oil Temperature Sensor Intermittent

P0200

Injector Circuit Malfunction

P0201

Injector Circuit Malfunction—Cylinder 1

P0202

Injector Circuit Malfunction—Cylinder 2

P0203

Injector Circuit Malfunction—Cylinder 3

P0204

Injector Circuit Malfunction—Cylinder 4

P0205

Injector Circuit Malfunction—Cylinder 5

P0206

Injector Circuit Malfunction—Cylinder 6

P0207

Injector Circuit Malfunction—Cylinder 7

P0208

Injector Circuit Malfunction—Cylinder 8

P0209

Injector Circuit Malfunction—Cylinder 9

P0210

Injector Circuit Malfunction—Cylinder 10

P0211

Injector Circuit Malfunction—Cylinder 11

P0212

Injector Circuit Malfunction—Cylinder 12

P0213

Cold Start Injector 1 Malfunction

P0214

Cold Start Injector 2 Malfunction

P0215

Engine Shutoff Solenoid Malfunction

P0216

Injection Timing Control Circuit Malfunction

P0217

Engine Overtemp Condition

P0218

Transmission Over Temperature Condition

P0219

Engine Overspeed Condition

P0220

Throttle/Pedal Position Sensor/Switch B Circuit Malfunction

P0221

Throttle/Pedal Position Sensor/Switch B Circuit Range/Performance Problem

P0222

Throttle/Pedal Position Sensor/Switch B Circuit Low Input

P0223

Throttle/Pedal Position Sensor/Switch B Circuit High Input

P0224

Throttle/Pedal Position Sensor/Switch B Circuit Intermittent

P0225

Throttle/Pedal Position Sensor/Switch C Circuit Malfunction

P0226

Throttle/Pedal Position Sensor/Switch C Circuit Range/Performance Problem

P0227

Throttle/Pedal Position Sensor/Switch C Circuit Low Input

P0228

Throttle/Pedal Position Sensor/Switch C Circuit High Input

P0229

Throttle/Pedal Position Sensor/Switch C Circuit Intermittent

P0230

Fuel Pump Primary Circuit Malfunction

P0231

Fuel Pump Secondary Circuit Low

P0232

Fuel Pump Secondary Circuit Intermittent

P0233

Fuel Pump Secondary Circuit Intermittent

P0234

Engine Overboost Condition

P0235

Turbocharger Boost Sensor A Circuit Malfunction

P0236

Turbocharger Boost Sensor A Circuit Range/Performance.

P0237

Turbocharger Boost Sensor A Circuit Low

P0238

Turbocharger Boost Sensor A Circuit High

P0239

Turbocharger Boost Sensor B Circuit Malfunction

P0240

Turbocharger Boost Sensor B Circuit Range/Performance

P0241

Turbocharger Boost Sensor B Circuit Low

P0242

Turbocharger Boost Sensor B Circuit High

P0243

Turbocharger Wastegate Solenoid A Malfunction

P0244

Turbocharger Wastegate Solenoid A Range/Performance

P0245

Turbocharger Wastegate Solenoid A Low

P0246

Turbocharger Wastegate Solenoid A High

P0247

Turbocharger Wastegate Solenoid B Malfunction

P0248

Turbocharger Wastegate Solenoid B Range/Performance

P0249

Turbocharger Wastegate Solenoid B Low

P0250

Turbocharger Wastegate Solenoid B High

P0251

Injection Pump Fuel Metering Control A Malfunction (Cam/Rotor/Injector)

P0252

Injection Pump Fuel Metering Control A Range/Performance (Cam/Rotor/Injector)

P0253

Injection Pump Fuel Metering Control A Low (Cam/Rotor/Injector)

P0254

Injection Pump Fuel Metering Control A High (Cam/Rotor/Injector)

P0255

Injection Pump Fuel Metering Control A Intermittent (Cam/Rotor/Injector)

P0256

Injection Pump Fuel Metering Control B Malfunction (Cam/Rotor/Injector)

P0257

Injection Pump Fuel Metering Control B Low (Cam/Rotor/Injector)

P0258

Injection Pump Fuel Metering Control B Low (Cam/Rotor/Injector)

P0259

Injection lump Fuel Metering Control B High (Cam/Rotor/Injector)

P0260

Injection Pump Fuel Metering Control B Intermittent (Cam/Rotor/Injector)

P0261

Cylinder 1 Injector Circuit Low

P0262

Cylinder 1 Injector Circuit High

P0263

Cylinder 1 Contribution/Balance Fault

P0264

Cylinder 2 Injector Circuit Low

P0265

Cylinder 2 Injector Circuit High

P0266

Cylinder 2 Contribution/Balance Fault

P0267

Cylinder 3 Injector Circuit Low

P0268

Cylinder 3 Injector Circuit High

P0269

Cylinder 3 Contribution/Balance Fault

P0270

Cylinder 4 Injector Circuit Low

P0271

Cylinder 4 Injector Circuit High

P0272

Cylinder 4 Contribution/Balance Fault

P0273

Cylinder 5 Injector Circuit Low

P0274

Cylinder 5 Injector Circuit High

P0275

Cylinder 5 Contribution/Balance Fault

P0276

Cylinder 6 Injector Circuit Low

P0277

Cylinder 6 Injector Circuit High

P0278

Cylinder 6 Contribution/Balance Fault

P0279

Cylinder 7 Injector Circuit Low

P0280

Cylinder 7 Injector Circuit High

P0281

Cylinder 7 Contribution/Balance Fault

P0282

Cylinder 8 Injector Circuit Low

P0283

Cylinder 8 Injector Circuit High

P0284

Cylinder 8 Contribution/Balance Fault

P0285

Cylinder 9 Injector Circuit Low

P0286

Cylinder 9 Injector Circuit High

P0287

Cylinder 9 Contribution/Balance Fault

P0288

Cylinder 10 Injector Circuit Low

P0289

Cylinder 10 Injector Circuit High

P0290

Cylinder 10 Contribution/Balance Fault

P0291

Cylinder 11 Injector Circuit Low

P0292

Cylinder 11 Injector Circuit High

P0293

Cylinder 11 Contribution/Balance Fault

P0294

Cylinder 12 Injector Circuit Low

P0295

Cylinder 12 Injector Circuit High

P0296

Cylinder 12 Contribution/Balance Fault

P0297

Vehicle Overspeed Condition

P0298

Engine Oil Over Temperature Condition

P0299

Turbocharger/Supercharger A Underboost Condition

P0300

Random/Multiple Cylinder Misfire Detected

P0301

Cylinder 1 Misfire Detected

P0302

Cylinder 2 Misfire Detected

P0303

Cylinder 3 Misfire Detected

P0304

Cylinder 4 Misfire Detected

P0305

Cylinder 5 Misfire Detected

P0306

Cylinder 6 Misfire Detected

P0307

Cylinder 7 Misfire Detected

P0308

Cylinder 8 Misfire Detected

P0309

Cylinder 9 Misfire Detected

P0310

Cylinder 10 Misfire Detected

P0311

Cylinder 11 Misfire Detected

P0312

Cylinder 12 Misfire Detected

P0313

Misfire Detected with Low Fuel

P0314

Single Cylinder Misfire (Cylinder Not Specified)

P0315

Crankshaft Position System Variation Not Learned

P0316

Misfire Detected on Startup (First 1000 Revolutions)

P0317

Rough Road Hardware Not Present

P0318

Rough Road Sensor A Signal Circuit

P0319

Rough Road Sensor B Signal Circuit

P0320

Ignition/Distributor Engine Speed Input Circuit Malfunction

P0321

Ignition/Distributor Engine Speed Input Circuit Range/Performance

P0322

Ignition/Distributor Engine Speed Input Circuit No Signal

P0323

Ignition/Distributor Engine Speed Input Circuit Intermittent

P0324

Single Cylinder Misfire (Cylinder Not Specified)

P0325

Knock Sensor 1 Circuit (Bank 2 or Single Sensor)

P0326

Knock Sensor 1 Circuit Range/Performance (Bank 2 or Single Sensor)

P0327

Knock Sensor 1 Circuit Low Input (Bank 2 or Single Sensor)

P0328

Knock Sensor 1 Circuit High Input (Bank 2 or Single Sensor)

P0329

Knock Sensor 1 Circuit Input Intermittent (Bank 2 or Single Sensor)

P0330

Knock Sensor 2 Circuit (Bank 2)

P0331

Knock Sensor 2 Circuit Range/Performance (Bank 2)

P0332

Knock Sensor 2 Circuit Low Input (Bank 2)

P0333

Knock Sensor 2 Circuit High Input (Bank 2)

P0334

Knock Sensor 2 Circuit Input Intermittent (Bank 2)

P0335

Crankshaft Position Sensor A Circuit Malfunction

P0336

Crankshaft Position Sensor A Circuit Range/Performance

P0337

Crankshaft Position Sensor A Circuit Low Input

P0338

Crankshaft Position Sensor A Circuit High Input

P0339

Crankshaft Position Sensor A Circuit Intermittent

P0340

Camshaft Position Sensor Circuit Malfunction

P0341

Camshaft Position Sensor Circuit Range/Performance

P0342

Camshaft Position Sensor Circuit Low Input

P0343

Camshaft Position Sensor Circuit High Input

P0344

Camshaft Position Sensor Circuit Intermittent

P0345

Camshaft Position Sensor A Circuit (Bank 2)

P0346

Camshaft Position Sensor A Circuit Range/Performance (Bank 2)

P0347

Camshaft Position Sensor A Circuit Low Input (Bank 2)

P0348

Camshaft Position Sensor A Circuit High Input (Bank 2)

P0349

Camshaft Position Sensor A Circuit Intermittent (Bank 2)

P0350

Ignition Coil Primary/Secondary Circuit Malfunction

P0351

Ignition Coil A Primary/Secondary Circuit Malfunction

P0352

Ignition Coil B Primary/Secondary Circuit Malfunction

P0353

Ignition Coil C Primary/Secondary Circuit Malfunction

P0354

Ignition Coil D Primary/Secondary Circuit Malfunction

P0355

Ignition Coil E Primary/Secondary Circuit Malfunction

P0356

Ignition Coil F Primary/Secondary Circuit Malfunction

P0357

Ignition Coil G Primary/Secondary Circuit Malfunction

P0358

Ignition Coil H Primary/Secondary Circuit Malfunction

P0359

Ignition Coil I Primary/Secondary Circuit Malfunction

P0360

Ignition Coil J Primary/Secondary Circuit Malfunction

P0361

Ignition Coil K Primary/Secondary Circuit Malfunction

P0362

Ignition Coil L Primary/Secondary Circuit Malfunction

P0363

Misfire Detected—Fueling Disabled

P0364

Camshaft Position Sensor (some applications) Reserved for Manufacturer Use (some applications)

P0365

Camshaft Position Sensor B Circuit (Bank 2)

P0366

Camshaft Position Sensor B Circuit Range/Performance (Bank 2)

P0367

Camshaft Position Sensor B Circuit Low Input (Bank 2)

P0368

Camshaft Position Sensor B Circuit High Input (Bank 2)

P0369

Camshaft Position Sensor B Circuit Intermittent (Bank 2)

P0370

Timing Reference High Resolution Signal A Malfunction

P0371

Timing Reference High Resolution Signal A Too Many Pulses

P0372

Timing Reference High Resolution Signal A Too Few Pulses

P0373

Timing Reference High Resolution Signal A Intermittent/Erratic Pulses

P0374

Timing Reference High Resolution Signal A No Pulses

P0375

Timing Reference High Resolution Signal B Malfunction

P0376

Timing Reference High Resolution Signal B Too Many Pulses

P0377

Timing Reference High Resolution Signal B Too Few Pulses

P0378

Timing Reference High Resolution Signal B Intermittent/Erratic Pulses

P0379

Timing Reference High Resolution Signal B No Pulses

P0380

Glow Plug/Heater Circuit A Malfunction

P0381

Glow Plug/Heater Indicator Circuit Malfunction

P0382

Glow Plug/Heater Circuit B Malfunction

P0383

Glow Plug Control Module Control Circuit Low

P0384

Glow Plug Control Module Control Circuit High

P0385

Crankshaft Position Sensor B Circuit Malfunction

P0386

Crankshaft Position Sensor B Circuit Range/Performance

P0387

Crankshaft Position Sensor B Circuit Low Input

P0388

Crankshaft Position Sensor B Circuit High Input

P0389

Crankshaft Position Sensor B Circuit Intermittent

P0390

Camshaft Position Sensor B Circuit (Bank 2)

P0391

Camshaft Position Sensor B Circuit Range/Performance (Bank 2)

P0392

Camshaft Position Sensor B Circuit Low Input (Bank 2)

P0393

Camshaft Position Sensor B Circuit High Input (Bank 2)

P0394

Camshaft Position Sensor B Circuit Intermittent (Bank 2)

P0395

Camshaft Position Sensor B Circuit High Input (Bank 2)

P0396

Camshaft Position Sensor B Circuit Intermittent (Bank 2)

P0400

Exhaust Gas Recirculation Flow Malfunction

P0401

Exhaust Gas Recirculation Flow Insufficient Detected

P0402

Exhaust Gas Recirculation Flow Excessive Detected

P0403

Exhaust Gas Recirculation Circuit Malfunction

P0404

Exhaust Gas Recirculation Circuit Range/Performance

P0405

Exhaust Gas Recirculation Sensor A Circuit Low

P0406

Exhaust Gas Recirculation Sensor A Circuit High

P0407

Exhaust Gas Recirculation Sensor B Circuit Low

P0408

Exhaust Gas Recirculation Sensor B Circuit High

P0409

Exhaust Gas Recirculation Sensor A Circuit

P0410

Secondary Air Injection System Malfunction

P0411

Secondary Air Injection System Incorrect Flow Detected

P0412

Secondary Air Injection System Switching Valve A Circuit Malfunction

P0413

Secondary Air Injection System Switching Valve A Circuit Open

P0414

Secondary Air Injection System Switching Valve A Circuit Shorted

P0415

Secondary Air Injection System Switching Valve B Circuit Malfunction

P0416

Secondary Air Injection System Switching Valve B Circuit Open

P0417

Secondary Air Injection System Switching Valve B Circuit Shorted

P0418

Secondary Air Injection System Relay A Circuit Malfunction

P0419

Secondary Air Injection System Relay B Circuit Malfunction

P0420

Catalyst System Efficiency Below Threshold (Bank 1)

P0421

Warm Up Catalyst Efficiency Below Threshold (Bank 1)

P0422

Main Catalyst Efficiency Below Threshold (Bank 1)

P0423

Heated Catalyst Efficiency Below Threshold (Bank 1)

P0424

Heated Catalyst Temperature Below Threshold (Bank 1)

P0425

Catalyst Temperature Sensor (Bank 1 Sensor 1)

P0426

Catalyst Temperature Sensor Range/Performance (Bank 1 Sensor 1)

P0427

Catalyst Temperature Sensor Low Input (Bank 1 Sensor 1)

P0428

Catalyst Temperature Sensor High Input (Bank 1 Sensor 1)

P0429

Catalyst Heater Control Circuit (Bank 1)

P0430

Catalyst System Efficiency Below Threshold (Bank 2)

P0431

Warm Up Catalyst Efficiency Below Threshold (Bank 2)

P0432

Main Catalyst Efficiency Below Threshold (Bank 2)

P0433

Heated Catalyst Efficiency Below Threshold (Bank 2)

P0434

Heated Catalyst Temperature Below Threshold (Bank 2)

P0435

Catalyst Temperature Sensor (Bank 2, Sensor 1)

P0436

Catalyst Temperature Sensor Range/Performance (Bank 2, Sensor 1)

P0437

Catalyst Temperature Sensor Low Input (Bank 2, Sensor 1)

P0438

Catalyst Temperature Sensor High Input (Bank 2, Sensor 1)

P0439

Catalyst Heater Control Circuit (Bank 2)

P0440

Evaporative Emission Control System Malfunction

P0441

Evaporative Emission Control System Incorrect Purge Flow

P0442

Evaporative Emission Control System Leak Detected (Small Leak)

P0443

Evaporative Emission Control System Purge Control Valve Circuit Malfunction

P0444

Evaporative Emission Control System Purge Control Valve Circuit Open

P0445

Evaporative Emission Control System Purge Control Valve Circuit Shorted

P0446

Evaporative Emission Control System Vent Control Circuit Malfunction

P0447

Evaporative Emission Control System Vent Control Circuit Open

P0448

Evaporative Emission Control System Vent Control Circuit Shorted

P0449

Evaporative Emission Control System Vent Valve/Solenoid Circuit Malfunction

P0460

Evaporative Emission Control System Pressure Sensor Malfunction

P0461

Evaporative Emission Control System Pressure Sensor Range/Performance

P0462

Evaporative Emission Control System Pressure Sensor Low Input

P0463

Evaporative Emission Control System Pressure Sensor High Input

P0464

Evaporative Emission Control System Pressure Sensor Intermittent

P0465

Evaporative Emission Control System Tank Detected (Gross Leak)

P0466

Evaporative Emission System Leak Detected (Very Small Leak)

P0467

Evaporative Emission System Leak Detected (Fuel Cap Loose/Off)

P0468

Evaporative Emission System Purge Control Valve Circuit Low

P0469

Evaporative Emission System Purge Control Valve Circuit High

P0460

Fuel Level Sensor Circuit Malfunction

P0461

Fuel Level Sensor Circuit Range/Performance

P0462

Fuel Level Sensor Circuit Low Input

P0463

Fuel Level Sensor Circuit High Input

P0464

Fuel Level Sensor Circuit Intermittent

P0465

Purge Flow Sensor Circuit Malfunction

P0466

Purge Flow Sensor Circuit Range/Performance

P0467

Purge Flow Sensor Circuit Low Input

P0468

Purge Flow Sensor Circuit High Input

P0469

Purge Flow Sensor Circuit Intermittent

P0470

Exhaust Pressure Sensor Malfunction

P0471

Exhaust Pressure Sensor Range/Performance

P0472

Exhaust Pressure Sensor Low

P0473

Exhaust Pressure Sensor High

P0474

Exhaust Pressure Sensor Intermittent

P0475

Exhaust Pressure Control Valve Malfunction

P0476

Exhaust Pressure Control Valve Range/Performance

P0477

Exhaust Pressure Control Valve Low

P0478

Exhaust Pressure Control Valve High

P0479

Exhaust Pressure Control Valve Intermittent

P0480

Cooling Fan 1 Control Circuit Malfunction

P0481

Cooling Fan 2 Control Circuit Malfunction

P0482

Cooling Fan 3 Control Circuit Malfunction

P0483

Cooling Fan Rationality Check Malfunction

P0484

Cooling Fan Circuit Over Current

P0485

Cooling Fan Power/Ground Circuit Malfunction

P0486

Exhaust Gas Recirculation Sensor B Circuit

P0487

Exhaust Gas Recirculation Throttle Position Control Circuit

P0488

Exhaust Gas Recirculation Throttle Position Control Range/Performance

P0489

Exhaust Gas Recirculation Control Circuit Low

P0490

Exhaust Gas Recirculation Control Circuit High

P0491

Secondary Air Injection System (Bank 2)

P0492

Secondary Air Injection System (Bank 2)

P0493

Fan Overspeed (Clutch Locked)

P0494

Fan Speed Low

P0495

Fan Speed High

P0496

Evaporative Emission System High Purge Flow

P0497

Evaporative Emission System Low Purge Flow

P0498

Evaporative Emission System Vent Control Circuit Low

P0499

Evaporative Emission System Vent Control Circuit High

P0500

Vehicle Speed Sensor Malfunction

P0501

Vehicle Speed Sensor Range/Performance

P0502

Vehicle Speed Sensor Circuit Low Input

P0503

Vehicle Speed Sensor Intermittent/Erratic/High

P0504

Brake Switch A/B Correlation

P0505

Idle Control System Malfunction

P0506

Idle Control System RPM Lower Than Expected

P0507

Idle Control System RPM Higher Than Expected

P0508

Idle Air Control System Circuit Low

P0509

Idle Air Control System Circuit High

P0510

Closed Throttle Position Switch Malfunction

P0511

Idle Air Control Circuit

P0512

Starter Request Circuit

P0513

Incorrect Immobilizer Key

P0514

Battery Temperature Sensor Circuit Range/Performance

P0515

Battery Temperature Sensor Circuit

P0516

Battery Temperature Sensor Circuit Low

P0517

Battery Temperature Sensor Circuit High

P0518

Idle Air Control Circuit Intermittent

P0519

Idle Air Control Circuit System Performance

P0520

Engine Oil Pressure Sensor/Switch Circuit Malfunction

P0521

Engine Oil Pressure Sensor/Switch Range/Performance

P0522

Engine Oil Pressure Sensor/Switch Low Voltage

P0523

Engine Oil Pressure Sensor/Switch High Voltage

P0524

Engine Oil Pressure Too Low

P0525

Cruise Control Servo Control Circuit Range/Performance

P0526

Fan Speed Sensor Circuit

P0527

Fan Speed Sensor Circuit Range/Performance

P0528

Fan Speed Sensor Circuit No Signal

P0529

Fan Speed Sensor Circuit Intermittent

P0530

A/C Refrigerant Pressure Sensor Circuit Malfunction

P0531

A/C Refrigerant Pressure Sensor Circuit Range/Performance

P0532

A/C Refrigerant Pressure Sensor Circuit Low Input

P0533

A/C Refrigerant Pressure Sensor Circuit High Input

P0534

Air Conditioner Refrigerant Charge Loss

P0535

A/C Evaporator Temperature Sensor Circuit

P0536

A/C Evaporator Temperature Sensor Circuit Range/Performance

P0537

A/C Evaporator Temperature Sensor Circuit Low

P0538

A/C Evaporator Temperature Sensor Circuit High

P0539

A/C Evaporator Temperature Sensor Circuit Intermittent

P0540

Intake Air Heater A Circuit

P0541

Intake Air Heater A Circuit Low

P0542

Intake Air Heater A Circuit High

P0543

Intake Air Heater A Circuit Open

P0544

Exhaust Gas Temperature Sensor Circuit—Bank 2 Sensor 1

P0545

Exhaust Gas Temperature Sensor Circuit Low—Bank 2 Sensor 1

P0546

Exhaust Gas Temperature Sensor Circuit High—Bank 2 Sensor 1

P0547

Exhaust Gas Temperature Sensor Circuit—Bank 2 Sensor 1

P0548

Exhaust Gas Temperature Sensor Circuit Low—Bank 2 Sensor 1

P0549

Exhaust Gas Temperature Sensor Circuit High—Bank 2 Sensor 1

P0550

Power Steering Pressure Sensor Circuit Malfunction

P0551

Power Steering Pressure Sensor Circuit Range/Performance

P0552

Power Steering Pressure Sensor Circuit Low Input

P0553

Power Steering Pressure Sensor Circuit High Input

P0554

Power Steering Pressure Sensor Circuit Intermittent

P0555

Brake Booster Pressure Sensor Circuit

P0556

Brake Booster Pressure Sensor Circuit Range/Performance

P0557

Brake Booster Pressure Sensor Circuit Low Input

P0558

Brake Booster Pressure Sensor Circuit High Input

P0559

Brake Booster Pressure Sensor Circuit Intermittent

P0560

System Voltage Malfunction

P0561

System Voltage Unstable

P0562

System Voltage Low

P0563

System Voltage High

P0564

Cruise Control Multi-Function Input A Circuit

P0565

Cruise Control On Signal Malfunction

P0566

Cruise Control Off Signal Malfunction

P0567

Cruise Control Resume Signal Malfunction

P0568

Cruise Control Set Signal Malfunction

P0569

Cruise Control Coast Signal Malfunction

P0570

Cruise Control Accel Signal Malfunction

P0571

Cruise Control/Brake Switch A Circuit Malfunction

P0572

Cruise Control/Brake Switch A Circuit Low

P0573

Cruise Control/Brake Switch A Circuit High

P0574

Cruise Control System—Vehicle Speed Too High

P0575

Cruise Control Input Circuit

P0576

Cruise Control Input Circuit Low

P0577

Cruise Control Input Circuit High

P0578

Cruise Control Multifunction Input A Circuit Stuck

P0579

Cruise Control Multifunction Input A Circuit Range/Performance

P0580

Cruise Control Multifunction Input A Circuit Low

P0581

Cruise Control Multifunction Input A Circuit High

P0582

Cruise Control Vacuum Control Circuit/Open

P0583

Cruise Control Vacuum Control Circuit Low

P0584

Cruise Control Vacuum Control Circuit High

P0585

Cruise Control Multifunction Input A/B Correlation

P0586

Cruise Control Vent Control Circuit/Open

P0587

Cruise Control Vent Control Circuit Low

P0588

Cruise Control Vent Control Circuit High

P0589

Cruise Control Multifunction Input B Circuit

P0590

Cruise Control Multifunction Input B Circuit Stuck

P0591

Cruise Control Multifunction Input B Circuit Range/Performance

P0592

Cruise Control Multifunction Input B Circuit Low

P0593

Cruise Control Multifunction Input B Circuit High

P0594

Cruise Control Servo Control Circuit/Open

P0595

Cruise Control Servo Control Circuit Low

P0596

Cruise Control Servo Control Circuit High

P0597

Thermostat Heater Control Circuit/Open

P0598

Thermostat Heater Control Circuit Low

P0599

Thermostat Heater Control Circuit High

P0600

Serial Communication Link Malfunction

P0601

Internal Control Module Memory Check Sum Error

P0602

Control Module Programming Error

P0603

Internal Control Module Keep Alive Memory (KAM) Error

P0604

Internal Control Module Random Access Memory (RAM) Error

P0605

Internal Control Module Read Only Memory (ROM) Error (Module Identification Defined by SAE J1979)

P0606

ECM/PCM Processor Fault

P0607

Control Module Performance

P0608

Control Module VSS Output A Malfunction

P0609

Control Module VSS Output B Malfunction

P0610

Control Module VSS Output B Malfunction

P0611

Fuel Injector Control Module Performance

P0612

Fuel Injector Control Module Relay Control Circuit

P0613

TCM Processor

P0614

ECM/TCM Mismatch

P0615

Starter Relay Circuit

P0616

Starter Relay Circuit Low

P0617

Starter Relay Circuit High

P0618

Alternative Fuel Control Module KAM Error

P0619

Alternative Fuel Control Module RAM/ROM Error

P0620

Generator Control Circuit Malfunction

P0621

Generator Lamp L Control Circuit Malfunction

P0622

Generator Field F Control Circuit Malfunction

P0623

Generator Lamp Control Circuit

P0624

Fuel Cap Lamp Control Circuit

P0625

Generator Field Terminal Circuit Low

P0626

Generator Field Terminal Circuit High

P0627

Fuel Pump A Control Circuit/Open

P0628

Fuel Pump A Control Circuit Low

P0629

Fuel Pump A Control Circuit High

P0630

VIN Not Programmed or Mismatch—ECM/PCM

P0631

VIN Not Programmed or Mismatch—TCM

P0632

Odometer Not Programmed—ECM/PCM

P0633

Immobilizer Key Not Programmed—ECM/PCM

P0634

PCM/ECM/TCM Internal Temperature Too High

P0635

Power Steering Control Circuit

P0636

Power Steering Control Circuit Low

P0637

Power Steering Control Circuit High

P0638

Throttle Actuator Control Range/Performance (Bank 1)

P0639

Throttle Actuator Control Range/Performance (Bank 2)

P0640

Intake Air Heater Control Circuit

P0641

Sensor Reference Voltage A Circuit/Open

P0642

Sensor Reference Voltage A Circuit Low

P0643

Sensor Reference Voltage A Circuit High

P0644

Driver Display Serial Communication Circuit

P0645

A/C Clutch Relay Control Circuit

P0646

A/C Clutch Relay Control Circuit Low

P0647

A/C Clutch Relay Control Circuit High

P0648

Immobilizer Lamp Control Circuit

P0649

Speed Control Lamp Control Circuit

P0650

Malfunction Indicator Lamp (MIL) Control Circuit Malfunction

P0651

Sensor Reference Voltage B Circuit/Open

P0652

Sensor Reference Voltage B Circuit Low

P0653

Sensor Reference Voltage B Circuit High

P0654

Engine RPM Output Circuit Malfunction

P0655

Engine Hot Lamp Output Control Circuit Malfunction

P0656

Fuel Level Output Circuit Malfunction

P0657

Actuator Supply Voltage Circuit/Open

P0658

Actuator Supply Voltage Circuit Low

P0659

Actuator Supply Voltage Circuit High

P0660

Intake Manifold Tuning Valve Control Circuit (Bank 1)

P0661

Intake Manifold Tuning Valve Control Circuit Low (Bank 1)

P0662

Intake Manifold Tuning Valve Control Circuit High (Bank 1)

P0663

Intake Manifold Tuning Valve Control Circuit (Bank 2)

P0664

Intake Manifold Tuning Valve Control Circuit Low (Bank 2)

P0665

Intake Manifold Tuning Valve Control Circuit High (Bank 2)

P0666

PCM/ECM/TCM Internal Temperature Sensor Circuit

P0667

PCM/ECM/TCM Internal Temperature Sensor Range/Performance

P0668

PCM/ECM/TCM Internal Temperature Sensor Circuit Low

P0669

PCM/ECM/TCM Internal Temperature Sensor Circuit High

P0670

Glow Plug Module Control Circuit

P0671

Cylinder 1 Glow Plug Circuit

P0672

Cylinder 2 Glow Plug Circuit

P0673

Cylinder 3 Glow Plug Circuit

P0674

Cylinder 4 Glow Plug Circuit

P0675

Cylinder 5 Glow Plug Circuit

P0676

Cylinder 6 Glow Plug Circuit

P0677

Cylinder 7 Glow Plug Circuit

P0678

Cylinder 8 Glow Plug Circuit

P0679

Cylinder 9 Glow Plug Circuit

P0680

Cylinder 10 Glow Plug Circuit

P0681

Cylinder 11 Glow Plug Circuit

P0682

Cylinder 12 Glow Plug Circuit

P0683

Glow Plug Control Module to PCM Communication Circuit

P0684

Glow Plug Control Module to PCM Communication Circuit Range/Performance

P0685

ECM/PCM Power Relay Control Circuit/Open

P0686

ECM/PCM Power Relay Control Circuit Low

P0687

ECM/PCM Power Relay Control Circuit High

P0688

ECM/PCM Power Relay Sense Circuit

P0689

ECM/PCM Power Relay Sense Circuit Low

P0690

ECM/PCM Power Relay Sense Circuit High

P0691

Fan 1 Control Circuit Low

P0692

Fan 1 Control Circuit High

P0693

Fan 2 Control Circuit Low

P0694

Fan 2 Control Circuit High

P0695

Fan 3 Control Circuit Low

P0696

Fan 3 Control Circuit High

P0697

Sensor Reference Voltage C Circuit/Open

P0698

Sensor Reference Voltage C Circuit Low

P0699

Sensor Reference Voltage C Circuit High

P0700

Transmission Control System Malfunction

P0701

Transmission Control System Range/Performance

P0702

Transmission Control System Electrical

P0703

Torque Converter/Brake Switch B Circuit Malfunction

P0704

Clutch Switch Input Circuit Malfunction

P0705

Transmission Range Sensor Circuit Malfunction (PRNDL Input)

P0706

Transmission Range Sensor Circuit Range/Performance

P0707

Transmission Range Sensor Circuit Low Input

P0708

Transmission Range Sensor Circuit High Input

P0709

Transmission Range Sensor Circuit Intermittent

P0710

Transmission Fluid Temperature Sensor Circuit Malfunction

P0711

Transmission Fluid Temperature Sensor Circuit Range/Performance

P0712

Transmission Fluid Temperature Sensor Circuit Low Input

P0713

Transmission Fluid Temperature Sensor Circuit High Input

P0714

Transmission Fluid Temperature Sensor Circuit Intermittent

P0715

Input/Turbine Speed Sensor Circuit Malfunction

P0716

Input/Turbine Speed Sensor Circuit Range/Performance

P0717

Input/Turbine Speed Sensor Circuit No Signal

P0718

Input/Turbine Speed Sensor Circuit Intermittent

P0719

Torque Converter/Brake Switch B Circuit Low

P0720

Output Speed Sensor Circuit Malfunction

P0721

Output Speed Sensor Circuit Range/Performance

P0722

Output Speed Sensor Circuit No Signal

P0723

Output Speed Sensor Circuit Intermittent

P0724

Torque Converter/Brake Switch B Circuit High

P0725

Engine Speed Input Circuit Malfunction

P0726

Engine Speed Input Circuit Range/Performance

P0727

Engine Speed Input Circuit No Signal

P0728

Engine Speed Input Circuit Intermittent

P0729

Gear 6 Incorrect Ratio

P0730

Incorrect Gear Ratio

P0731

Gear 1 Incorrect Ratio

P0732

Gear 2 Incorrect Ratio

P0733

Gear 3 Incorrect Ratio

P0734

Gear 4 Incorrect Ratio

P0735

Gear 5 Incorrect Ratio

P0736

Reverse Incorrect Ratio

P0737

TCM Engine Speed Output Circuit

P0738

TCM Engine Speed Output Circuit Low

P0739

Timing Reference High Resolution Signal B No Pulses

P0740

Torque Converter Clutch Circuit Malfunction

P0741

Torque Converter Clutch Circuit Performance or Stuck Off

P0742

Torque Converter Clutch Circuit Stuck On

P0743

Torque Converter Clutch Circuit Electrical

P0744

Torque Converter Clutch Circuit Intermittent

P0745

Pressure Control Solenoid Malfunction

P0746

Pressure Control Solenoid Performance or Stuck Off

P0747

Pressure Control Solenoid Stuck On

P0748

Pressure Control Solenoid Electrical

P0749

Pressure Control Solenoid Intermittent

P0750

Shift Solenoid A Malfunction

P0751

Shift Solenoid A Performance or Stuck Off

P0752

Shift Solenoid A Stuck On

P0753

Shift Solenoid A Electrical

P0754

Shift Solenoid A Intermittent

P0755

Shift Solenoid B Malfunction

P0756

Shift Solenoid B Performance or Stuck Off

P0757

Shift Solenoid B Stuck On

P0758

Shift Solenoid B Electrical

P0759

Shift Solenoid B Intermittent

P0760

Shift Solenoid C Malfunction

P0761

Shift Solenoid C Performance or Stuck Off

P0762

Shift Solenoid C Stuck On

P0763

Shift Solenoid C Electrical

P0764

Shift Solenoid C Intermittent

P0765

Shift Solenoid D Malfunction

P0766

Shift Solenoid D Performance or Stuck Off

P0767

Shift Solenoid D Stuck On

P0768

Shift Solenoid D Electrical

P0769

Shift Solenoid D Intermittent

P0770

Shift Solenoid E Malfunction

P0771

Shift Solenoid E Performance or Stuck Off

P0772

Shift Solenoid E Stuck On

P0773

Shift Solenoid E Electrical

P0774

Shift Solenoid E Intermittent

P0775

Pressure Control Solenoid B

P0776

Pressure Control Solenoid B Performance or Stuck Off

P0777

Pressure Control Solenoid B Stuck On

P0778

Pressure Control Solenoid B Electrical

P0779

Pressure Control Solenoid B Intermittent

P0780

Shift Malfunction

P0781

1-2 Shift Malfunction

P0782

2-3 Shift Malfunction

P0783

3-4 Shift Malfunction

P0784

4-5 Shift Malfunction

P0785

Shift Timing Solenoid A Malfunction

P0786

Shift Timing Solenoid A Range/Performance

P0787

Shift Timing Solenoid A Low

P0788

Shift Timing Solenoid A High

P0789

Shift Timing Solenoid A Intermittent

P0790

Normal/Performance Switch Circuit Malfunction

P0791

Intermediate Shaft Speed Sensor Circuit

P0792

Intermediate Shaft Speed Sensor Circuit Range/Performance

P0793

Intermediate Shaft Speed Sensor Circuit No Signal

P0794

Intermediate Shaft Speed Sensor Circuit Intermittent

P0795

Pressure Control Solenoid C

P0796

Pressure Control Solenoid C Performance or Stuck Off

P0797

Pressure Control Solenoid C Stuck On

P0798

Pressure Control Solenoid C Electrical

P0799

Pressure Control Solenoid C Intermittent

P0800

Transmission Control System (MIL Request)

P0801

Reverse Inhibit Control Circuit Malfunction

P0802

Transmission Control System MIL Request Circuit/Open

P0803

1-4 Upshift (Skip Shift) Solenoid Control Circuit Malfunction

P0804

1-4 Upshift (Skip Shift) Lamp Control Circuit Malfunction

P0805

Clutch Position Sensor Circuit Malfunction

P0806

Clutch Position Sensor Circuit Range/Performance Malfunction

P0807

Clutch Position Sensor Circuit Low Malfunction

P0808

Clutch Position Sensor Circuit High Malfunction

P0809

Clutch Position Sensor Circuit Intermittent Malfunction

P0810

Clutch Position Control Error

P0811

Excessive Clutch Slippage

P0812

Reverse Input Circuit

P0813

Reverse Output Circuit

P0814

Transmission Range Display Circuit

P0815

Upshift Switch Circuit

P0816

Downshift Switch Circuit

P0817

Starter Disable Circuit

P0818

Driveline Disconnect Switch Input Circuit

P0819

Up and Down Shift Switch to Transmission Range Correlation

P0820

Gear Lever X-Y Position Sensor Circuit

P0821

Gear Lever X Position Circuit

P0822

Gear Lever Y Position Circuit

P0823

Gear Lever X Position Circuit Intermittent

P0824

Gear Lever Y Position Circuit Intermittent

P0825

Gear Lever Push-Pull Switch (Shift Anticipate)

P0826

Up and Down Switch Input Circuit

P0827

Up and Down Switch Input Circuit Low

P0828

Up and Down Switch Input Circuit High

P0829

5-6 Shift

P0830

Clutch Pedal Switch A Circuit

P0831

Clutch Pedal Switch A Circuit Low

P0832

Clutch Pedal Switch A Circuit High

P0833

Clutch Pedal Switch B Circuit

P0834

Clutch Pedal Switch B Circuit Low

P0835

Clutch Pedal Switch B Circuit High

P0836

Four Wheel Drive (4WD) Switch Circuit

P0837

Four Wheel Drive (4WD) Switch Circuit Range/Performance

P0838

Four Wheel Drive (4WD) Switch Circuit Low

P0839

Four Wheel Drive (4WD) Switch Circuit High

P0840

Transmission Fluid Pressure Sensor/Switch A Circuit

P0841

Transmission Fluid Pressure Sensor/Switch A Circuit Range/Performance

P0842

Transmission Fluid Pressure Sensor/Switch A Circuit Low

P0843

Transmission Fluid Pressure Sensor/Switch A Circuit High

P0844

Transmission Fluid Pressure Sensor/Switch A Circuit Intermittent

P0845

Transmission Fluid Pressure Sensor/Switch B Circuit

P0846

Transmission Fluid Pressure Sensor/Switch B Circuit Range/Performance

P0847

Transmission Fluid Pressure Sensor/Switch B Circuit Low

P0848

Transmission Fluid Pressure Sensor/Switch B Circuit High

P0849

Transmission Fluid Pressure Sensor/Switch B Circuit Intermittent

P0850

Park/Neutral Switch Input Circuit

P0851

Park/Neutral Switch Input Circuit Low

P0852

Park/Neutral Switch Input Circuit High

P0853

Drive Switch Input Circuit

P0854

Drive Switch Input Circuit Low

P0855

Drive Switch Input Circuit High

P0856

Traction Control Input Signal

P0857

Traction Control Input Signal Range/Performance

P0858

Traction Control Input Signal Low

P0859

Traction Control Input Signal High

P0860

Gear Shift Module Communication Circuit

P0861

Gear Shift Module Communication Circuit Low

P0862

Gear Shift Module Communication Circuit High

P0863

TCM Communication Circuit

P0864

TCM Communication Circuit Range/Performance

P0865

TCM Communication Circuit Low

P0866

TCM Communication Circuit High

P0867

Transmission Fluid Pressure

P0868

Transmission Fluid Pressure Low

P0869

Transmission Fluid Pressure High

P0870

Transmission Fluid Pressure Sensor/Switch C Circuit

P0871

Transmission Fluid Pressure Sensor/Switch C Circuit Range/Performance

P0872

Transmission Fluid Pressure Sensor/Switch C Circuit Low

P0873

Transmission Fluid Pressure Sensor/Switch C Circuit High

P0874

Transmission Fluid Pressure Sensor/Switch C Circuit Intermittent

P0875

Transmission Fluid Pressure Sensor/Switch D Circuit

P0876

Transmission Fluid Pressure Sensor/Switch D Circuit Range/Performance

P0877

Transmission Fluid Pressure Sensor/Switch D Circuit Low

P0878

Transmission Fluid Pressure Sensor/Switch D Circuit High

P0879

Transmission Fluid Pressure Sensor/Switch D Circuit Intermittent

P0880

TCM Power Input Signal

P0881

TCM Power Input Signal Range/Performance

P0882

TCM Power Input Signal Low

P0883

TCM Power Input Signal High

P0884

TCM Power Input Signal Intermittent

P0885

TCM Power Relay Control Circuit/Open

P0886

TCM Power Relay Control Circuit Low

P0887

TCM Power Relay Control Circuit High

P0888

TCM Power Relay Sense Circuit

P0889

TCM Power Relay Sense Circuit Range/Performance

P0890

TCM Power Relay Sense Circuit Low

P0891

TCM Power Relay Sense Circuit High

P0892

TCM Power Relay Sense Circuit Intermittent

P0893

Multiple Gears Engaged

P0894

Transmission Component Slipping

P0895

Shift Time Too Short

P0896

Shift Time Too Long

P0897

Transmission Fluid Deteriorated

P0898

Transmission Control System MIL Request Circuit Low

P0899

Transmission Control System MIL Request Circuit High

P0900

Clutch Actuator Circuit/Open

P0901

Clutch Actuator Circuit Range/Performance

P0902

Clutch Actuator Circuit Low

P0903

Clutch Actuator Circuit High

P0904

Gate Select Position Circuit (Senses Left/Right Position)

P0905

Gate Select Position Circuit Range/Performance

P0906

Gate Select Position Circuit Low

P0907

Gate Select Position Circuit High

P0908

Gate Select Position Circuit Intermittent

P0909

Gate Select Control Error

P0910

Gate Select Actuator Circuit/Open (Left/Right Motion)

P0911

Gate Select Actuator Circuit Range/Performance

P0912

Gate Select Actuator Circuit Low

P0913

Gate Select Actuator Circuit High

P0914

Gear Shift Position Circuit (Senses Forward/Rearward Position, Odd/Even Gears)

P0915

Gear Shift Position Circuit Range/Performance

P0916

Gear Shift Position Circuit Low

P0917

Gear Shift Position Circuit High

P0918

Gear Shift Position Circuit Intermittent

P0919

Gear Shift Position Control Error

P0920

Gear Shift Forward Actuator Circuit/Open (Forward Motion, Odd Gears, 1,3,5)

P0921

Gear Shift Forward Actuator Circuit Range/Performance

P0922

Gear Shift Forward Actuator Circuit Low

P0923

Gear Shift Forward Actuator Circuit High

P0924

Gear Shift Reverse Actuator Circuit/Open (Rearward Motion, Even Gears, 2,4,6)

P0925

Gear Shift Reverse Actuator Circuit Range/Performance

P0926

Gear Shift Reverse Actuator Circuit Low

P0927

Gear Shift Reverse Actuator Circuit High

P0928

Gear Shift Lock Solenoid Circuit/Open

P0929

Gear Shift Lock Solenoid Circuit Range/Performance

P0930

Gear Shift Lock Solenoid Circuit Low

P0931

Gear Shift Lock Solenoid Circuit High

P0932

Hydraulic Pressure Sensor Circuit

P0933

Hydraulic Pressure Sensor Range/Performance

P0934

Hydraulic Pressure Sensor Circuit Low Input

P0935

Hydraulic Pressure Sensor Circuit High Input

P0936

Hydraulic Pressure Sensor Circuit Intermittent

P0937

Hydraulic Oil Temperature Sensor Circuit

P0938

Hydraulic Oil Temperature Sensor Range/Performance

P0939

Hydraulic Oil Temperature Sensor Circuit Low Input

P0940

Hydraulic Oil Temperature Sensor Circuit High Input

P0941

Hydraulic Oil Temperature Sensor Circuit Intermittent

P0942

Hydraulic Pressure Unit

P0943

Hydraulic Pressure Unit Cycling Period Too Short

P0944

Hydraulic Pressure Unit Loss of Pressure

P0945

Hydraulic Pump Relay Circuit/Open

P0946

Hydraulic Pump Relay Circuit Range/Performance

P0947

Hydraulic Pump Relay Circuit Low

P0948

Hydraulic Pump Relay Circuit High

P0949

ASM Adaptive Learning Not Done

P0950

ASM Control Circuit

P0951

ASM Control Circuit Range/Performance

P0952

ASM Control Circuit Low

P0953

ASM Control Circuit High

P0954

ASM Control Circuit Intermittent

P0955

ASM Mode Circuit

P0956

ASM Mode Circuit Range/Performance

P0957

ASM Mode Circuit Low

P0958

ASM Mode Circuit High

P0959

ASM Mode Circuit Intermittent

P0960

Pressure Control Solenoid A Control Circuit/Open

P0961

Pressure Control Solenoid A Control Circuit Range/Performance

P0962

Pressure Control Solenoid A Control Circuit Low

P0963

Pressure Control Solenoid A Control Circuit High

P0964

Pressure Control Solenoid B Control Circuit/Open

P0965

Pressure Control Solenoid B Control Circuit Range/Performance

P0966

Pressure Control Solenoid B Control Circuit Low

P0967

Pressure Control Solenoid B Control Circuit High

P0968

Pressure Control Solenoid C Control Circuit/Open

P0969

Pressure Control Solenoid C Control Circuit Range/Performance

P0970

Pressure Control Solenoid C Control Circuit Low

P0971

Pressure Control Solenoid C Control Circuit High

P0972

Shift Solenoid A Control Circuit Range/Performance

P0973

Shift Solenoid A Control Circuit Low

P0974

Shift Solenoid A Control Circuit High

P0975

Shift Solenoid B Control Circuit Range/Performance

P0976

Shift Solenoid B Control Circuit Low

P0977

Shift Solenoid B Control Circuit High

P0978

Shift Solenoid C Control Circuit Range/Performance

P0979

Shift Solenoid C Control Circuit Low

P0980

Shift Solenoid C Control Circuit High

P0981

Shift Solenoid D Control Circuit Range/Performance

P0982

Shift Solenoid D Control Circuit Low

P0983

Shift Solenoid D Control Circuit High

P0984

Shift Solenoid E Control Circuit Range/Performance

P0985

Shift Solenoid E Control Circuit Low

P0986

Shift Solenoid E Control Circuit High

P0987

Transmission Fluid Pressure Sensor/Switch E Circuit

P0988

Transmission Fluid Pressure Sensor/Switch E Circuit Range/Performance

P0989

Transmission Fluid Pressure Sensor/Switch E Circuit Low

P0990

Transmission Fluid Pressure Sensor/Switch E Circuit High

P0991

Transmission Fluid Pressure Sensor/Switch E Circuit Intermittent

P0992

Transmission Fluid Pressure Sensor/Switch F Circuit

P0993

Transmission Fluid Pressure Sensor/Switch F Circuit Range/Performance

P0994

Transmission Fluid Pressure Sensor/Switch F Circuit Low

P0995

Transmission Fluid Pressure Sensor/Switch F Circuit High

P0996

Transmission Fluid Pressure Sensor/Switch F Circuit Intermittent

P0997

Shift Solenoid F Control Circuit Range/Performance

P0998

Shift Solenoid F Control Circuit Low

P0999

Shift Solenoid F Control Circuit High

© Jones & Bartlett Learning.

Appendix D Vehicle Emissions Control Information Label Vehicle emissions control labels began to appear on vehicles in the early 1970s and were initially located on the engine rocker cover or radiator support. Most manufacturers now locate this label on the engineside surface of the hood, and it may be referred to as the underhood emissions label (FIGURE D-1). This label provides important information for the engine performance diagnostic technician:

FIGURE D-1 The underhood emissions label provides important information for the engine performance diagnostic technician.

Description

Vehicle model year (MY) VIN barcode for some vehicles Engine family: JFMXT3.54JK Engine size (cylinder displacement): 3.5L The emissions standards to which the vehicle conforms, either U.S. EPA or California (sometimes both) The EVAP family code The emissions control components used on the vehicle: Any adjustments that can be made that relate to engine or emissions performance The label in Figure D-1 shows this to be a 2018 MY vehicle with engine family JFMXT3.54JK of 3.5 L V6. It conforms to California ULEV70 LDT (ultra low emissions vehicle) standards. The vehicle has the following emissions control equipment: TWC (three-way catalysts, 4, two on each cylinder bank) DFI (direct fuel injection) SFI (sequential fuel injection) WR-HO2S (wide range heated oxygen sensors, one on each cylinder bank) HO2S (heated oxygen sensors, one on each cylinder bank) TC (Turbo charger) CAC (charge air cooler for turbocharge intake air cooling) AIR (Air injection system) SFI (Sequential fuel injection) EVAP system JFMXR0260NDP No adjustments needed The label has a part number and is specific to the vehicle equipped with this engine for 2018 that is sold in California and other states that have adopted California emissions standards. The technician uses this information to verify the vehicle MY, the engine family, the engine size, whether the vehicle is built to meet California or U.S. EPA emissions standards, and what emissions control systems are used on this vehicle. Technicians performing emissions tests also use the information on this label during the visual inspection of the emissions test procedure. U.S. EPA labels may not have any information regarding California emissions or they may state that they do not meet or are not certified to meet California emissions standards (FIGURE D-2). This does not mean that a U.S. EPA level vehicle cannot ever be used in California (or states that require those emissions levels). A vehicle owner can move into California and register the vehicle once it has passed an emissions inspection and test. The emissions test technician will enter the data that this vehicle is a U.S. EPA-level vehicle and not a California-level vehicle into the test system. The system then adjusts related test data parameters so that the vehicle is tested against U.S. EPA emissions levels applicable for the model year, vehicle type, and engine size.

FIGURE D-2 A vehicle that is certified only to U.S. EPA standards does not state that it meets California emissions standards and was not originally sold in California (or a state that has adopted the California emissions standards).

Description Technicians may encounter a vehicle where the VECI label is missing or is incorrect. This is usually due to a collision repair that required replacement of the hood. A replacement hood will not have a label as part of the assembly. A used hood from a recycling yard may have the wrong label, due to a different model year, emissions certification, or engine family. Emissions labels are not easily replaced. They are usually a special-order item from the new vehicle dealer, and the dealer often requires a form to be filled out and verified by the parts counter person with respect to vehicle VIN and production date. Should you encounter a vehicle that has a missing or incorrect VECI label, recommend that a correct label be sourced and installed on the vehicle. This will save the customer a great deal of trouble in areas where emissions testing is required as part of vehicle registration.

© Jones & Bartlett Learning.

Glossary 3 Cs A term used to describe the repair documentation process of 1st documenting the customer concern, 2nd documenting the cause of the problem, and 3rd documenting the correction. 5-Gas analyzer A tool that uses sensors to measure the level of gases in the exhaust stream. Active motor mounts Engine mounts that change in relation to engine operation to stop stray vibrations depending on the operational situation. A/F sensor Abbreviation for the air–fuel ratio sensor. This sensor determines the air-to-fuel ratio based on oxygen levels in the engine exhaust gas. Aftermarket A company other than the original manufacturer that produces equipment or provides services. ASM 15/25 dyno test Acceleration Simulation Model dyno-type emissions test. Usually a shorter and easier to perform dyno-based emissions drive pattern with the vehicle operated at 15 mph under heavy load and 25 mph at light load. Atkinson cycle engine An engine cycle that uses a longer effective exhaust stroke than intake stroke to reduce exhaust emissions. This type of engine is widely used in hybrid electric vehicles. Automotive stethoscope Tool that includes a long, solid metal probe at the end that, when held against a solid component, transfers sound to the earpieces. Available Scan tool data that indicate the identified noncontinuous monitor is installed on the vehicle. Bank 1 and Bank 2 An identifier for the location of the fuel trim data (and related A/F or HO2S sensor) on the engine. Some manufacturers use cylinder 1 as the location for Bank 1 whereas others may choose the side of a V-type or boxer-type engine layout. Inline engines have only one cylinder bank. Base ignition timing adjustment The manual setting of initial ignition timing until the PCM advances or retards the ignition timing for engine operation. California Air Research Board (CARB) The state organization charged with protecting the public from the harmful effects of air pollution and developing programs and actions to fight climate change. Camshaft position (CMP) sensor A detection device that signals to the PCM the rotational position of the camshaft. Canister vent valve A solenoid that allows fresh air to enter the evaporative system during a purge event. Also used for an evaporative system monitoring test. Carbon dioxide (CO2) A colorless, odorless gas that exists naturally in the air, it also results from burning a hydrocarbon fuel, contributing to global warming. Carbon monoxide (CO) A colorless, odorless gas that is highly toxic and causes asphyxiation when

inhaled. It is produced through incomplete fuel burning, such as with vehicle emissions. Cause Part of the 3 Cs, documenting the cause of the problem. This documentation will go on the repair order, invoice, and service history. Coil near plug (CNP) A type of ignition system used on late-model vehicles that uses one coil placed near each spark plug with a small spark plug wire attached to the spark plug. Coil on plug (COP) A type of ignition system used on late-model vehicles that uses one coil placed above each spark plug. Complete Scan tool data that indicate the related monitor has successfully run. It does not mean it has passed, only that the test or tests are complete. Component monitor An OBD II test run to ensure that a specific component or system is working properly. Concern Part of the 3 Cs, documenting the original concern that the customer came into the shop with. This documentation will go on the repair order, invoice, and service history. Continuous monitors OBD II monitors the fuel system, engine misfires, and components (inputs and outputs) continuously when the ignition is ON and when required, such as for misfires, when the engine is running. Correction Part of the 3 Cs, documenting the repair that solved the vehicle fault. This documentation will go on the repair order, invoice, and service history. Crankshaft position (CKP) sensor A sensor used by the PCM to monitor engine speed. It can be one of three types of sensors—Hall effect, magnetic pickup, or optical. Data link connector (DLC) The underdash connector through which the scan tool communicates to the vehicle’s computers; it displays the readings from the various sensors and can retrieve trouble codes, freeze frame data, and system monitor data. Data maps Specifications that have been set by the original equipment manufacturer (OEM) per sensor, which allows the PCM to make decisions based on sensor outputs. Decoupler pulleys High-tech pulleys that provide belt-drive power to the alternator during acceleration and cruising speeds. Delta Pressure Feedback EGR (DPFE) sensor A sensor for pressure differential within an exhaust system to verify EGR operation. Detonation The reaction when the spark plug ignites the air-fuel, as it should; however, the flame front initiated by the spark plug collides with an undesired flame front. Dielectric grease A silicone-based grease that repels moisture and protects electrical connections. Drive cycle Defined by the manufacturer, it verifies the operation of a power train input sensor, output actuator, or the integrity of a system (e.g., EGR). Each is defined by the related monitors with which it is associated and is detailed in the service information for each monitored component or system. DTC structure Standardized format followed by OBD II powertrain DTCs. It begins with the letter P and is followed by four numbers or a combination of numbers and letters. Each character is associated with the type of DTC, the related system, and component. Duty cycle The percentage of one period of time in which the circuit is powered ON. EGR valve position sensors A sensor located in the EGR valve that monitors the position of pintle within the component. The sensor may be analog or digital. Electrode The hottest part of the spark plug and the path of least resistance, it allows the electrical current coming from the coil to get close the ground strap where it arcs to complete the circuit. That

arc is what ignites the fuel within the cylinder. Enabling conditions The operation conditions required before a monitor is allowed to run. Engine control module (ECM) Computer that operates the fuel and ignition systems on later model vehicles. Engine OFF natural vacuum (EONV) EVAP leak test A test that runs after the vehicle is parked and the engine is OFF. The PCM monitors ambient temperature; once the temperature has dropped enough, it will begin the test sequence. The PCM closes the vent valve to seal the EVAP system. The PCM then monitors the fuel tank pressure sensor for a drop in pressure as the fuel cools overnight and creates a negative pressure in the EVAP system. Environmental Protection Agency (EPA) A U.S. federal government agency that deals with issues related to environmental safety. Evaporative emissions system (EVAP) A system used to capture vapors or gases from an evaporating liquid. EVAP vapor storage canister A device used to trap the fuel vapors. The fuel vapors adhere to the charcoal until the engine is started, and engine vacuum can be used to draw (purge) the vapors into the engine so that they can be burned along with the air–fuel mixture. Exhaust back pressure Pressure buildup in the exhaust system related to restriction of flow of exhaust fumes through the system. Exhaust gas recirculation (EGR) A valve that allows a controlled amount of exhaust gas into the intake manifold during a certain period of engine operation. Used to lower nitrogen oxide exhaust emissions. Fail Scan tool data that indicate a noncontinuous monitor has run, completed, and failed. Freeze frame data Refers to snapshots that are automatically stored in a vehicle’s power train control module (PCM) when a fault occurs (only available on model year 1996 and newer). Front-end accessory drive (FEAD) component A front-end accessory drive component is anything that is driven off the front of the engine. Fuel map The program that is run by the PCM that relates engine load to rpm. It provides the fuel injector with the correct amount of on-time to increase engine performance. Fuel pump module This consists of a fuel pump, fuel level sensor, fuel tank pressure sensor, and hanger. Fuel tank pressure sensor (FTP) A sensitive pressure sensor mounted in the fuel tank or EVAP system and used to monitor the system for leaks. Fuel trim The fueling strategy that is used by the PCM. Gasoline direct fuel injection (GDI) Engines that inject the fuel into the cylinder so that the PCM can inject the fuel at the optimum moment for efficient combustion. Hexadecimal A base 16 method of counting. High-pressure fuel pump The engine-driven pump used on a GDI engine. HO2S Abbreviation for heated oxygen sensor. This sensor detects exhaust gas oxygen in the form of a varying voltage signal. Hydrocarbons (HC) Microscopic unburned fuel particles that contribute to photochemical smog and help form ground-level ozone. IM 240 dyno test A very thorough drive cycle test for the Inspection and Maintenance (smog) emissions system test. This test mirrors the EPA Federal Test Procedure (FTP) test drive cycle.

Incomplete Scan tool data that indicate a monitor test has not run. This may be due to an incomplete drive cycle or enable conditions were not met. Injector duration The amount of time (usually in ms) the injector is switched ON. Intermittent faults A fault or customer concern that you cannot detect all of the time and only occurs sometimes. Internal combustion engines (ICE) An engine that burns a fuel internally and creates movement due to thermal expansion of gases. Leak detection pump This system uses a small pump assembly that uses engine vacuum for pump operation, and it places the system into a vacuum situation which then the PCM measures FTP decay to determine if the system has a leak. Logic gates An electronic component that reacts to the zeros and ones. ECU processors incorporate logic gates. Long-term fuel trim (LTFT) Calculated by the PCM based on how the engine is operating currently, it directs long-term engine operation. Magneto reluctance (MR) sensor A sensor that uses the principle of magnetic induction to create its signal. It is used to measure rotational speed, including wheel speed, machine speed, engine speed, and camshaft and crankshaft position. Magneto resistive/Hall-effect (MRE) sensor A type of wheel speed sensor that uses an effect similar to a Hall-effect sensor to create its signal. Malfunction threshold The limit(s) that monitor data must exceed to set a pending or current DTC. This is found in the related DTC information. Misfire monitor An OBD II test that monitors engine misfires and alerts the driver if there is a misfire. Monitor description An explanation of what the monitor is watching and what it is looking for. Monitor strategy A brief list of information on how and when the monitor runs during engine operation found in the DTC information. Noise, vibration, and harshness (NVH) Automotive vibrations and harsh operations that need to be diagnosed as a customer concern. Noncontinuous monitors Monitors that run only once per drive cycle. NOx A sensor that detects oxygen ions originating from nitric oxide (NOx) from among the other oxygen ions present in the exhaust gas. OBD II DLC emissions test Later OBD II vehicles may be eligible for this test, in which the emissions analyzer connects to the DLC and reviews OBD II monitor test results to determine if the vehicle passes or fails. This test still requires a visual inspection and smoke test. OBD noncontinuous monitor OBD II monitors computerized engine controls for proper operation, they run at specific times during the drive cycle or when the vehicle is OFF. On-board diagnostic first generation (OBD I) system The first generation of onboard diagnostic systems that originated for California vehicles. On-board diagnostic second generation (OBD II) system The second generation of onboard diagnostic systems, which have been in effect for all U.S. vehicles since 1996. One-way clutch (OWC) pulley A clutch on an alternator that drives only one way and slips the opposite way. Original equipment manufacturer (OEM) The company that manufactured the vehicle.

Overrunning alternator decoupler (OAD) This decouples the alternator to eliminate it as a source of vibration when it is not needed. Oxides of nitrogen (NOx) A vehicle emission that contributes to ground-level ozone, they are produced when nitrogen and oxygen react during combustion, given sufficient temperatures and pressures. Forms include nitrogen oxide and nitrogen dioxide. Oxygen (O2) A colorless, odorless reactive gas, the chemical element of atomic number 8 and the lifesupporting component of the air. Oxygen or A/F sensor heater monitor The OBD II monitor that detects a fault for the heater or heater circuit. Oxygen or A/F sensor monitor The OBD II monitor that verifies oxygen or air–fuel ratio sensor operation is within test limits. Parameter ID (PID) Used to identify each value that is monitored by the PCM. PCM monitor OBD II monitor that runs continuously or noncontinuously throughout the drive cycle. Position sensor A sensor that monitors the position of a component. The sensor may be analog or digital. Some monitor the movement of a component, such as an HVAC blend air door or the engine throttle blade, as it moves from one position to another. Others monitor the location of rotating components, such as the crankshaft. Powertrain control module (PCM) Computer that operates the fuel and ignition systems on later model vehicles. Purge control valve A valve used to control the flow of evaporative emissions from the charcoal canister to the intake manifold. Repair order The document that is given to the repair technician that details the customer concern and any needed information. Scan tool modes Scan tool communication with the PCM follows OBD policy and regulations from related agencies, including the EPA and CARB. Secondary air system monitor The monitor verifies the secondary air system delivers fresh air to the exhaust. Service advisor The person at a repair facility that is in charge of communicating with the customer. Service history A complete listing of all the servicing and repairs that have been performed on that vehicle. Service information Vehicle repair information that is available for the technician to repair the vehicle. Short-term fuel trim (STFT) A calculation that determines the amount of fuel the engine is using and adjusts based on the upstream oxygen sensor signal. Smart battery charger A microprocessor-controlled battery charger that can be used to charge various types of batteries without overcharging them. Spark knock An erratic form of combustion that occurs when the ignition process is not controlled by the spark plug. Stoichiometric ratio The optimum ratio of air to fuel for combustion—14.7 parts air to 1 part fuel by weight. Strategy-based diagnostic process A systematic process used to diagnose faults in a vehicle. Stratified charge mode A layering of a lean air–fuel mixture in the combustion chamber. It is used when the fuel injector and piston head place fuel near the spark plug but not the surrounding space.

Technical service bulletin (TSB) Information issued by a manufacturer to alert technicians of expected problems or changes to repair procedures. Trip A completed drive cycle that is also associated with DTCs. Some components or systems require only one where a fault is detected for a DTC to store and turn the MIL ON. Others require two consecutive trips with a detected fault before a DTC stores and the MIL illuminates. Two-speed idle test A nondynamometer-type emissions test, performed at 2500 rpm and engine idle speed to measure exhaust emissions. Two-trip DTC A DTC that requires two consecutive trips for the malfunction threshold to exceed limits to store a DTC and illuminate the MIL. A pending DTC stores on the first trip. Variable valve timing (VVT) The advancement or retarding of individual camshafts to increase engine performance. Vehicle Emission Control Information (VECI) A decal located under the hood in a variety of locations: on top of the core support, on a strut tower, or on the underside of the vehicle’s hood are frequently used positions. The decal lists the installed emission control devices, the year the vehicle’s emission system conforms to, and which OBD system is used. Wire tachometer An inexpensive tool used to determine the rpm at which a noise or vibration is occurring. A wire is used to monitor the vibration, and the tool indicates the rpm.

© Jones & Bartlett Learning.

Index NOTE: Page numbers followed by f, or t indicate materials in figures, or tables respectively.

A abnormal combustion-preignition and detonation, 341–342 detonation, 342–343, 343f, 343t preignition, 342, 342f, 343t abnormal fuel trim values, 198–199 active listening skills, 3–5, 4f active motor mounts, 339 adjustable valves, 337 ADP. See alternator decoupler pulleys (ADP) advanced computerized engine control diagnostics data processing, 24–27, 25f, 26f, 27t ECM/PCM operation review, 24, 24f engine control module inspection, 37–39, 38f engine control service information. See engine control service information power train control system diagram, 27–31, 28f, 29f, 30f advanced ignition system diagnosis DTC-based ignition system diagnosis, 125–128, 126–128f inspect CKP/CMP sensors, 115–120f, 115–123 inspect ignition timing, 124, 124f knock sensor operation, 124–125, 125f no DTC-based ignition system diagnosis, 128–133, 128–133f OBD II ignition, 106–107, 106–107f plug and ignition coil operation without coil disassembly, 110–111, 110f spark plugs, inspection of, 111–115f, 111–115 spark testing, 107–109, 108f advanced ignition timing, 301 AF sensor. See air-fuel (AF) sensor aftermarket, 3 replacement catalytic converters, 265, 266f aftermarket source, 9, 9f air-fuel ratio, 300–304, 301f heater circuit testing, 223–228, 224–225f, 227f sensors, 53, 224f air-fuel (AF) sensor, 219, 223f, 228 heater circuit, 225–226 air-to-air intercooler, 91, 91f alternator decoupler pulleys (ADP), 335 APS/TPS sensors, 53 ASE L1 Advanced Engine Performance composite vehicle diagram, 29, 30f ASM 15/25 IM testing, 308–312 Atkinson cycle engines, 255–256, 256f automotive stethoscope, 330, 331–332 available oxygen, 214–215

B Bank 1 sensors, 215, 224f, 256 Bank 2 sensors, 215, 256 base ignition timing adjustment, 124 bottom-end engine noise, 334

C California Air Research Board (CARB), 300 cam position (CMP) sensor, 118–119, 130, 132f camshaft and valve train, 333 camshaft position (CMP) data, 131, 131f sensor, 106, 124 camshaft VVT actuator fault, 173 CAN. See Controller Area Network (CAN) CARB. See California Air Research Board (CARB) carbon dioxide (CO2), 298, 300 carbon monoxide (CO), 298 catalyst monitor, 173, 174f catalyst operation, 256–259, 257–259f catalyst system monitor DTC cause, 259–266, 260f, 264f catalyst systems operation, 256, 256f, 257f cause, 16, 16f chassis ear, 331–332 check mode, 8, 158, 159f check valves, 230 Chevrolet Tahoe 2008 (case study), 162–163 CKP sensors. See crankshaft position (CKP) sensors climate change, 300 CMP. See camshaft position (CMP) CMP sensor. See cam position (CMP) sensor CNP. See coil near plug (CNP) CO. See carbon monoxide (CO) CO2. See carbon dioxide (CO2) coil near plug (CNP), 106 coil on plug (COP), 106 systems, 107f, 114 testers, 110, 110f complete conversion of hydrocarbon, 214 component monitor, 184–189, 185–189f, 188f diagnostic (case study), 189–190 concern, 16, 16f continuous monitor diagnostics, 184 case study, 189–190, 189f, 190f component monitor, 184–189, 185–189f fuel system monitor, 197, 197f fuel trim, 197–198, 197–198f data cells, 199–200, 200f, 201f diagnosis with smoke machine, 199, 199f DTCs, 200–203, 201f, 202f values, abnormal, 198–199 misfire monitor, 190–196, 190–196f OBD II continuous monitors, 184, 184f, 185f continuous monitors, 150, 184, 184f, 185f operation, 187 Controller Area Network (CAN) protocol, 141 signals, 142, 142f control module, 38 control valves, 230 coolant consumption, 348–349, 348f coolant dye testing, 349, 349f COP. See coil on plug (COP)

correction, 16, 16f crankshaft position (CKP) sensors, 29, 32, 53, 106, 115–120, 115–120f, 130, 132f crankshaft revolution, 333 customer comebacks, 6 customer’s concern, verifying, 6–7f, 6–8 cylinder misfire, 193f

D data link connector (DLC), 141, 141f, 163–165, 163–165f scan tool communication, 164f data look-up tables, 27, 27t data maps, 27, 28f, 197 data processing, 24–27, 25f, 26f, 27t decoupler pulleys, 335 Delta Pressure Feedback EGR (DPFE) sensor, 246 detonation, 342–343, 343f, 343t causes of, 343–344 diagnostic trouble codes (DTCs), 7–8, 31–32, 32f, 149–151, 150f, 151f actual hands-on diagnostics for, 76 based ignition system diagnosis, 125–128, 126–128f clear, 153–154 current, 151–152, 152f diagnostics, 32–35, 34f, 75, 75f, 190, 191f engine performance, 34f history, 152–153, 152f information, 32, 33f, 185, 186f inspection procedures, 33f, 76, 76f parameter data, 177 permanent, 153, 153f structures, 143 dielectric grease, 115, 132, 132f digital multimeter (DMM), 71, 114 digital storage oscilloscope (DSO), 60, 219, 332, 332f direct injection system diagnosis DS-4 PFI/GDI diagnosis (case study), 101–102, 102f gasoline direct fuel injection (GDI), 88–91, 88–91f fuel system cleaning, 96–98, 96f operation of combination PFI and, 99–101, 99–101f system maintenance, 94–96 high-pressure fuel pump diagnosis, 91–92f, 91–93 DLC. See data link connector (DLC) DLC BOB. See DLC breakout box (DLC BOB) DLC breakout box (DLC BOB), 165–166, 165f DMM. See digital multimeter (DMM) documentation of repair, 16–17, 16f parts of, 17 repair order, 17, 17f DPFE sensor. See Delta Pressure Feedback EGR (DPFE) sensor drive cycle, 150 DSO. See digital storage oscilloscope (DSO) DS-4 PFI/GDI diagnosis (case study), 101–102, 102f DTCs. See diagnostic trouble codes (DTCs) duty cycle, 247

E ECM. See engine control module (ECM) ECM/PCM operation review. See engine control module/powertrain control module (ECM/PCM) operation review ECT. See engine coolant temperature (ECT) ECU. See engine control unit (ECU) EGR effect. See gas recirculation (EGR) effect EGR operation. See exhaust gas recirculation (EGR) operation EGR system monitor operation, 248–250, 249–250f Atkinson cycle engines, 255–256, 256f

system leaks or blockage, 254–255, 255f valve inspection, 250–256, 252f variable valve time, 255, 255f electrodes, 106 electronic EGR valves, 250, 252f emissions inspection and maintenance testing methods, 304–306, 305–306f ASM 15/25 IM testing, 308–312 handbook, 312 IM 240 emissions test, 306, 308, 308f system diagnosis, 313–317, 315–317f system standards, 312–313, 313t two-speed idle test, 306, 307f emissions levels, 300–304, 301f enabling conditions, 185, 188f engine control intermittent fault check procedures, 35–37, 36f engine control module (ECM), 24, 24f, 140 chart, 35, 35f inspection, 37–39, 38f power source circuit, 130 engine control module/powertrain control module (ECM/PCM) operation review, 24, 24f data processing, 24–27, 25f, 26f, 27t engine control service information, 31 DTC diagnostics, 32–35, 34f ECM/PCM terminal ID and related signal values, 35, 35f engine control intermittent fault check procedures, 35–37, 36f technical service bulletins (TSBs), 31, 31f trouble code service information, 31–32, 32f, 33f wiring diagram, 37, 37f engine control system diagram, 27–29, 28f, 29f engine control unit (ECU), 67, 140 engine control wiring diagram, 37f engine coolant temperature (ECT), 185 data, 148 wiring diagram, 190f engine emissions testing and failure diagnosis emissions inspection and maintenance testing methods, 304–306, 305–306f ASM 15/25 IM testing, 308–312 handbook, 312 IM 240 emissions test, 306, 308, 308f system diagnosis, 313–317, 315–317f system standards, 312–313, 313t two-speed idle test, 306, 307f perfect and incomplete combustion, 298, 298f air-fuel ratio and emissions levels, 300–304, 301f carbon dioxide and climate change, 300 vehicle emissions, early efforts to control, 298–300, 299f engine noises, diagnosing, 330–332, 330f, 332f bottom-end engine noise, 334 determining location, 332 front-of-engine noise, 334–336, 334–335f fuel injector noise, 332–333, 333f rear-of-engine noise, 336, 336f speed of noise to isolate fault, 336 top-end engine noise, 333–334, 333f engine OFF natural vacuum (EONV) EVAP leak test, 283 engine temperature, 189f Environmental Protection Agency (EPA), 298 EPA. See Environmental Protection Agency (EPA) EVAP. See evaporative emissions system (EVAP) evaporative emissions system (EVAP), 272 engine OFF natural vacuum (EONV) EVAP leak test, 283 fuel cap testing, 288 hydrocarbon vapors, 272, 273f leak detection pump type, 281–282f, 281–283 monitor test results analysis, 278

nonvented fuel cap, 272, 273f operation, 272, 273f purge flow monitor analysis, 283, 284f purge valve, 272–277, 274f system faults and related diagnostic and repair procedures, 284–285f, 284–289, 289f vacuum-type leak monitor, 278–279f, 278–281 vapor storage canister, 272 vent valve, 277–278, 277f exhaust back pressure, 245 exhaust gas recirculation (EGR) operation, 244–248, 244f, 248f monitor diagnostics, 250f monitor test, 249f systems, 246f, 247f, 248f valve, 245f, 246f

F fail, 216 fail-safe data, 178, 179f FIPG. See form-in-place-gasket (FIPG) 5-gas analyzer, 300, 302–304 focused testing, 9–13, 10–12f customer approval of repair, 14 pay attention to details, 15 performing repair, 13 take time to perform repair, 13–14 updates prior to repair, 14 use correct tool for job, 13 use proper service procedures, 13, 14f Ford Escape Hybrid, 256, 256f form-in-place-gasket (FIPG), 132 freeze frame data, 8 front-end accessory drive (FEAD) component, 334 front-of-engine noise, 334–335f, 334–336 FTP sensor. See fuel tank pressure (FTP) sensor fuel cap testing, 288 fuel injectors, 52, 53f, 60f, 61f cleaning station, 60, 60f faults, 59 noise, 332–333, 333f O-rings, 62f partially clogged, 60f fuel map, 53 fuel monitor, 174, 174f fuel pump module, 62 service procedures, 62–65, 65f testing, 65–66f, 65–67 fuel-related no-start faults, 132 fuel system feedback, 215 fuel system monitor, 197, 197f fuel tank pressure (FTP) sensor, 226f, 278–280 fuel trim, 52, 197–198, 197–198f data cells, 199–200, 200f, 201f diagnosis with smoke machine, 199, 199f DTCs, 200–203, 201f, 202f long-term, 197, 198f short-term, 197, 198f values, abnormal, 198–199 fuel trim diagnostic (case study), 202–206, 204–206f

G gasoline direct fuel injection (GDI), 88–91, 88–91f, 332–333, 333f advantage of, 99

carbon buildup on valves, 96, 96f fuel pump faults, 91, 92f fuel system cleaning, 96–98, 96f fuel tank, 89f high-pressure fuel, 91, 91f injector noise, 101, 101f injector seals, 94–96 injector spray patterns, 100, 101f internal pump failure, 92 operation of combination PFI and, 99–101, 99–101f system maintenance, 94–95, 96 turbocharged, 100 gas recirculation (EGR) effect, 99 GDI. See gasoline direct fuel injection (GDI) Generic Scan Tool mode, 166, 166f

H HC. See hydrocarbons (HC) head gasket failure and coolant loss, 349–350, 350f combustion leak detector, 351–352, 351f exhaust gas analyzer, 352–353 failed head gasket diagnosis, 350–351, 351f heated air-fuel ratio sensor operation, 219–223, 222–223f, 224f heated oxygen sensor, 214–219, 214–216f, 219f heated oxygen sensor Bank 1 (HO2S1B1), 215 hexadecimal format, 146, 146f, 147f high-pressure fuel pump, 88 high-pressure fuel pump diagnosis, 91–92f, 91–93 high-tech drivetrain mounts, 340, 341f high-tech motor mounts, 340–341, 341f HO2 sensors, 227–228 hydraulic mount, 341, 341f hydrocarbons (HC), 298

I IAT/ECT sensors, 53 ICE. See internal combustion engines (ICE) ignition coil, 110, 110f ignition system, 8 ignition timing, 124, 124f verifying knock sensor operation, 124–125, 125f ignition trigger, 110, 110f IM 240 emissions test, 306, 308, 308f immobilizer system, 130 inaccurate ignition timing, 124 injector duration, 197 input sensors, 53 intake fuel pump module, 66, 66f intermittent faults, 7, 36f internal combustion engines (ICE), 99, 107 internal EGR effect, 301

K Karman Vortex MAF sensor, 77, 78f knock sensor operation, 124–125, 125f

L LDP. See leak detection pump (LDP) leak detection pump (LDP), 278, 281–282f, 281–283 light bulb circuit, 11 light load conditions, 90

logic gate, 24–25, 25f brake light switch input data, 26f long-term fuel trim (LTFT), 52, 53, 197, 198f LTFT. See long-term fuel trim (LTFT)

M MAF. See mass airflow (MAF) magneto reluctance (MR), 115 magneto resistive CKP sensors, 116–117, 116f magneto resistive/Hall effect (MRE), 115 malfunction indicator lamp (MIL), 125 manifold absolute pressure sensor, 72, 73f MAP sensors, 73, 73f mass airflow (MAF), 73, 73f, 77, 77f DTC P0103 diagnostics, 76, 77f fault, 173 sensor inspection, 78–79 sensors, 53, 73, 73f, 75, 76f signal (case study), 73–79, 74–78f MIL. See malfunction indicator lamp (MIL) misfire counts, 128, 129f, 191, 192, 192f misfire monitors, 184, 190–196, 190–196f diagnostic (case study), 196–197 information, 193, 193f monitor description, 185 monitor strategy, 229 monitor test, 175, 176–177f results analysis, 278 motor mount faults, 339 diagnosing standard motor mounts, 339–340, 340f high-tech motor mounts, 340–341, 341f MR. See magneto reluctance (MR) MRE CKP/CMP signal, 120f MR sensor, 116–117, 116f

N negative temperature coefficient, 68 no DTC-based ignition system diagnosis, 128–133, 128–133f noises in engine, 330–332, 330f, 332f bottom-end engine noise, 334 determining location, 332 front-of-engine noise, 334–336, 334–335f fuel injector noise, 332–333, 333f listening tools, 330, 330f rear-of-engine noise, 336, 336f speed of noise to isolate fault, 336 top-end engine noise, 333–334, 333f transmission, 330 noise, vibration, and harshness (NVH), 330. See also noises in engine noncontinuous monitors test components, 175, 175f nonvented fuel cap, 272, 273f novice technicians, 13 NOx. See oxides of nitrogen (NOx) values, 245f NVH. See noise, vibration, and harshness (NVH)

O OAD. See overrunning alternator decoupler (OAD) OBD II. See on-board diagnostic second generation (OBD II) system OBD I system. See on-board diagnostic first generation (OBD I) system OEM. See original equipment manufacturer (OEM) oil consumption testing, 345, 345f

coolant consumption, 348–349, 348f coolant dye testing, 349, 349f oil leak diagnosis, 347 oil pressure testing, 345–347, 346f PCV case study, 347–348, 348f oil leak diagnosis, 347 oil pressure testing, 345–347, 346f on-board diagnostic first generation (OBD I) system, 140 on-board diagnostic second generation (OBD II) system, 139 advanced scan tool functions, 157–161, 158f aspects of, 141f catalyst systems operation, 256–259, 257–259f Chevrolet Tahoe 2008 (case study), 162–163 continuous monitors, 184, 184f, 185f data link connector (DLC), 163–165, 163–165f data list, 177–178, 178–179f drive cycles, 166–171, 169f, 170f, 171f heated oxygen sensor operation, 214–216, 214–216f ignition, 106–107, 106–107f monitor test, 175, 176–177f OBD II application, 140–142f, 140–143 one-trip and two-trip diagnostic trouble codes, 171–173, 172f, 173f, 174f oxygen sensor heater circuit analysis, 216–217, 217f role of, 162, 162f scan tool modes, 145–148, 146–147f, 159–161 clear DTCs, 153–154 current DTCs, 151–152, 152f data display, 148–149, 148–149f diagnostic trouble codes, 149–151, 150f, 151f freeze frame data, 149, 149f functional tests, 155–156, 155f history diagnostic trouble codes, 152–153, 152f monitors, enable criteria, and drive cycle, 150–151 monitor test results, 154–155, 154f permanent diagnostic trouble codes, 153, 153f vehicle information, 156–157, 157f structure, 143–144, 143–144f Toyota Tacoma 1999 (case study), 144–145, 145f system monitors, 173–177, 174–177f one-way clutch (OWC) pulleys, 335 on-vehicle fuel injector, 59, 60f original equipment manufacturer (OEM), 3 overrunning alternator decoupler (OAD), 335, 335f OWC pulleys. See one-way clutch (OWC) pulleys oxides of nitrogen (NOx), 244, 298 oxygen (O2), 298 oxygen sensor, 228 output voltage, 219f oxygen sensor heater, 218 circuit analysis, 216–217, 217f monitor, 216, 217f

P parameter ID (PID), 190 PCM. See power train control module (PCM) PCM 5-V reference, 130 P0420 Code (case study), 260, 263–264 PCV (case study), 347–348, 348f perfect and incomplete combustion, 298, 298f air-fuel ratio and emissions levels, 300–304, 301f carbon dioxide and climate change, 300 vehicle emissions, early efforts to control, 298–300, 299f PFI system. See port fuel injection (PFI) system PID. See parameter ID (PID)

piezoelectric GDI injectors, 88, 89f piston slap diagnosis, 334 port fuel injection (PFI) system component review, 52–53, 52–53f fuel pump service procedures, 62–65, 65f fuel pump testing, 65–66f, 65–67 injector diagnosis and service, 59–62, 60–62f MAF signal (case study), 73–79, 74–78f position sensor testing procedures, 71–73, 71f pressure sensor and mass airflow sensors, 71, 73, 73f service information, 54, 54f switch input testing procedures, 67–68, 68f system–related faults, 54 temperature sensor testing procedures, 68–70, 69f wiring diagram, 54–55f, 54–59 position sensor testing procedures, 71–73, 71f positive crankcase ventilation (PCV) system, 132 power train control module (PCM), 8, 24, 24f, 38, 38f, 39, 106, 124, 187f, 246 functions to control, 100 monitors, 88, 219 processing speed, 99 software calibration, 39 power train control system diagram, 27–31, 28f, 29f, 30f Pre-CAT oxygen sensors, 215, 216f preignition, 342, 342f, 343t problem symptoms table, 128, 129f purge flow monitor analysis, 283, 284f purge valve, 272–277, 274f

R rear-of-engine noise, 336, 336f recall notice, 3, 4f repair order, 2, 2f, 17–18, 17f rocker cover spark plug, 132, 132f

S scan tool, 146, 147f, 148f, 148t, 149f, 150f, 191, 192f misfire count data, 193f scan tool modes, 145–148, 146–147f clear DTCs, 153–154 current DTCs, 151–152, 152f data display, 148–149, 148–149f diagnostic trouble codes, 149–151, 150f, 151f freeze frame data, 149, 149f functional tests, 155–156, 155f history diagnostic trouble codes, 152–153, 152f monitors, enable criteria, and drive cycle, 150–151 monitor test results, 154–155, 154f permanent diagnostic trouble codes, 153, 153f vehicle information, 156–157, 157f secondary air systems, 216, 228–229, 228f for air leaks, 231–232 check valves, 230–232, 231f monitor, 229, 229f test, 229 sensor 1 (S1), 215 sensor 2 (S2), 215 sensor circuits, 77 sensor operation, 29, 130, 130f service advisor, 3–4 service history, vehicle, 2–3, 2f, 4f active listening skills, 3–5, 4f service information, 27, 28f, 36f, 54, 54f, 178, 178f

short-term fuel trim (STFT), 53, 197, 198f smart battery charger, 38 smoke-generating machine, 230 smoke test machine, 230, 231f spark knock, 112 spark plug inspection of, 111–112f, 111–113, 115 wires, 113–115f, 113–115 spark tester, 108–109 spark testing, 107–109, 108f, 132 plug and ignition coil operation without coil disassembly, 110–111, 110f speed of noise to isolate fault, 336 standard motor mounts, 339, 340f stethoscope, 336, 336f STFT. See short-term fuel trim (STFT) stoichiometric ratio, 244 strategy-based diagnostics, 2 documentation of repair, 16–17, 16f parts of documentation, 17 repair order, 17–18, 17f focused testing, 9–13, 10–12f customer approval of repair, 14 pay attention to details, 15 performing repair, 13 take time to perform repair, 13–14 updates prior to repair, 14 use correct tool for job, 13 use proper service procedures, 13, 14f need for, 5–6, 6f researching possible faults and gathering information, 8–9, 8–9f vehicle service history, 2–3, 2f, 4f active listening skills, 3–5, 4f verifying customer’s concern, 6–7f, 6–8 verifying repair, 15 stratified charge mode, 90 symptoms information, 34f system faults and related diagnostic and repair procedures, 284–285f, 284–289, 289f system leaks or blockage, 254–255, 255f

T task description, 13, 14f technical service bulletins (TSBs), 9, 9f, 14, 31, 31f, 156–157 technician researching service information, 7, 7f technicians novice, 13 safety on tests, 12, 12f Teflon seal, 94, 94f temperature collection, 27, 27t temperature sensor testing procedures, 68–70, 69f temperature switch, 68, 68f test equipment and procedures, 13 test record, 10, 10f thermostat fault, 173 3 Cs: concern, cause, and correction, 17, 17f top-end engine noise, 333–334, 333f Toyota DS-4 intake, 99, 100f Toyota Prius, 256, 256f Toyota Tacoma 1999 (case study), 144–145, 145f trouble code service information, 31–32, 32f, 33f TSBs. See technical service bulletins (TSBs) turbocharger, 90, 90f two-speed idle test, 306, 307f two-trip DTCs, 219

U ultrasonic fuel injector cleaner, 60, 60f underhood emission labels, 162, 162f

V vacuum EGR valves, 250 vacuum-type leak monitor, 278–279f, 278–281 valve inspection, 250–256, 252f valve overlap, 99 valve timing, 131–132 valve train components, 331 valve train noises, 336–337, 337f timing chain noise, 337–339, 338–339f variable valve timing (VVT), 99, 255, 255f control, 99 VECI. See Vehicle Emission Control Information (VECI) label vehicle computer architecture, 141 Vehicle Emission Control Information (VECI) label, 142, 143f vehicle emissions, 298–300, 299f vehicle identification number (VIN), 31, 156 vent valve, 277–278, 277f VIN. See vehicle identification number (VIN) visual inspection, 7, 7f, 12 voltage supply, 11 VVT. See variable valve timing (VVT)

W walnut shell blasting, 96, 96f warranty, 16 “water hammer” effect, 333 wideband air-fuel (AF) ratio sensor, 219, 222f wide band sensors, 227–228 wire tachometer, 330–332 wiring diagram, 37, 37f

Z Zirconia oxygen sensor diagnosis, 220–221

The recall bulletin issued for fuel system, gasoline is titled as, N H T S A recall bulletin, and shows details such as reference number, vehicle description, system of the vehicle involved, description of the defect that needs to be addressed during the service, consequence of the described defect, and corrective action to be taken by the service provider. Back to Figure The steps are as follows: give individual attention, maintain eye contact, avoid interrupting, ask questions to verify understanding, and pay attention to nonverbal messages such as tone of voice, body language. Back to Figure The steps involved are as follows: Step 1: Verify the customer’s concern, Step 2: Research possible faults and gather information, Step 3: Focused testing, Step 4: Perform the repair, and Step 5: Verify the repair. Back to Figure The technical service bulletin issued for slow cracking, dead battery and or no start shows details such as reference number, service information including brand of the vehicle, model, model year, VIN, engine number, involved region or country, condition, cause, and correction required. Back to Figure The thoughts and test description of the technician read as follows: Well, the vacuum reading is 15 inches at idle which is below normal. I will record that on the repair order as follows: Test Description: Vacuum test: Expectation: 18 inches to 21 inches at idle; Result: 15 inches at idle, below normal. Back to Figure The list of questions is as follows: Ok Safety Check, When was this hoist last certified? Am I using the hoist correctly? Are the arm locks functioning? Is the center of gravity right for this vehicle? Are the lift pads positioned properly? Is my PPE appropriate? I think I am ready to start work now. Back to Figure

The technician said to the customer, Your concern was the check engine light on. The cause was a fuel pressure sensor. To correct the fault we have replaced the pressure sensor, cleared the code, and road tested your car which is now performing normally. The customer replied to the technician, Thank you so much for your explanation. Back to Figure The invoice shows details such as invoice number, customer number, service provider company logo, service advisor number, customer details, vehicle details, details about the repair done, and the respective charges involved. Back to Figure One of the pathways shows engine control module leading to fuel injection, ignition system, and valve assembly. Collectively, this leads to combustion chamber, which further leads to crankshaft. Another pathway from engine control module leads to E G R, which further leads to A I S. A third pathway shows the following components in sequence: intake air from atmosphere, throttle, A I S, combustion chamber, exhaust system, and exhaust emissions to atmosphere. Exhaust system further leads to E G R. Back to Figure There are four columns: Symbol, name, algebraic expression, truth TABLE. There are eight rows and the data from the TABLE presented in the format: Name, Algebraic expression are as follows. Row 1: Buffer, A. Row 2: Not, A bar. Row 3: And, A B. Row 4: NAND, A B bar. Row 5: OR, A plus B. Row 6: NOR, A plus B bar. Row 7: XOR, tensor product of A and B. Row 8: XNOR, tensor product of A and B bar. Truth TABLE and symbol for the data are also listed in the TABLE. Back to Figure It has on the vertical axis, fuelling in the range of 0 to 130 in equal intervals of 10, along the horizontal axis, engine R P M in the range of 9000 to 500 in equal intervals of 500. Load sites in the range of 0 to 15 in equal intervals of 3 are shown. Back to Figure

Crankshaft position sensor, Air fuel ratio sensor, and heated oxygen sensor are shown. The relay is connected to the wiring shield in Crankshaft position sensor, and air fuel ratio sensor. Outside these shows a flow from battery through E F I MAIN Number 2 and E F I MAIN 2 to splice point. Splice point is connected to fuel ratio sensor, and heated oxygen sensor. Back to Figure Change vehicle tab selected. Text on screen reads, P o 117, engine coolant temperature sensor circuit low. A diagram with title, FIGURE 1, Engine coolant temperature sensor circuit wiring diagram is followed by text, for a complete wiring diagram refer to appropriate system wiring diagrams article. Back to Figure The change vehicle tab is selected. An arrow to go back to PO117 is available. Text on screen reads, Active DTC, Step 1: start the engine and allow it reach normal operating temperature. Followed by a warning and a note. Step 2: with the scan tool select view DTC. Is the DTC active at this time? If yes, go to a link, and if no, refer to intermittent condition and perform the intermittent diagnostic procedure ECT sensor, Step 1: turn the ignition off. Step 2: disconnect the ECT harness connector. Step 3: ignition on, engine not running. Step 4: with the scan tool read ECT voltage. Back to Figure Change vehicle tab selected. A TABLE labeled, FIGURE 1. Engine control system symptom chart, basic 1 of 2 is shown. Back to Figure Text reads, under inspection, inspect crankshaft position sensor. A FIGURE titled, fig 1, identifying crankshaft position sensor connector is followed by text that reads, measure the resistance according to the value in the TABLE below. Tester connection 1 to 2, condition is cold, specified condition is 1630 to 2740. Condition hot then specified condition is 2065 to 3225. Back to Figure 2 a r- f e, diagnostics introduction, except hybrid, page. A FIGURE illustrating connector terminal identification is followed by a hint and a TABLE with

columns: terminal number symbol, wiring color, terminal description, condition, specified condition. Back to Figure 2 a r- f e, diagnostics introduction, except hybrid, page. The check for intermittent problems, 08 by 2015 option is expanded. Hints follow. Other options like basic inspection, registration are listed. Back to Figure Point four, symptom simulation is elaborated with hint and examples. Vibration method, when a malfunction seems to occur as a result of vibration. A FIGURE illustrating identifying vibration method is shown with title, Vibration method, when a malfunction seems to occur as a result of vibration. Back to Figure There are four ignition coil assembly, four fuel injector assembly, Certification E C U, smart key E C U assembly, park or neutral position switch assembly, starter assembly, stop light switch assembly, engine switch, fuel pump, battery, relays, etcetera are labeled. Back to Figure Purge V S V, Vacuum switching valve, Mass air flow meter sub-assembly, Vent valve, canister pressure sensor, leak detection pump, canister pump module, transmission control switch, knock control sensor, intake air control valve actuator for tumble control valve, from park or neutral position switch assembly, throttle with motor body assembly, generator, combination meter assembly are labeled. Back to Figure There are four columns. Row data are as follows: A25-51, VPA -A25-52, EPA; G- y; Accelerator pedal position sensor signal, for engine control; Ignition switch ON, accelerator pedal fully released, 0.5 to 1.1 V. Row 2: A25-51, VPA -A25-52, EPA; G- y; Accelerator pedal position sensor signal, for engine control; Ignition switch ON, accelerator pedal fully depressed; 2.6 to 4.5 V. Row 3: A25-54, V P A 2 –A 25-55, E P A 2; R B E; Accelerator pedal position sensor signal; Ignition switch ON, accelerator pedal fully released; 1.2 to 2.0 V. Row 4: A 25-54, V P A

2 -A25-55, E P A 2; R B E; Accelerator pedal position sensor signal; Ignition switch ON, accelerator pedal fully depressed; 3.4 to 4.75 V. Row 5: A25-53, V C P A –A 25-52, E P A; P- Y; power source of accelerator pedal position sensor for V P A; ignition switch on; 4.5 to 5.5 V. Row 6: A25-56, V C P2 -A25-55, E P A2; L- B E; power source of accelerator pedal position sensor for V P A 2; ignition switch on; 4.5 to 5.5 V. Row 7: E 26-23, H A 1 A –E 26-53, E 04; G- WB; Air fuel ratio sensor heater operation signal; Idling; Pulse generation, See waveform 3. Row 8: E26-23, H A 1 A- E 26-53, E 04; G- W- B; Air fuel ratio sensor heater operation signal; Ignition switch on; 11 to 14 V. Row 9: E 26-133, A I A plus –E 26-16, E 1; L- B R; Air fuel ratio sensor signal; Ignition switch on; 3.3 V. Row 10: E 26-134, A I A -E26-16, E1; P- B R; Air fuel ratio sensor signal; Ignition switch on; 2.9 V. Row 11: E 26-24, H T 1 B –E 26-53, E 04; Y- W- B; Heated oxygen sensor heater operation signal; Idling; below 3.0 V. Row 12: E 26-24, H T 1 B –E 26-53, E 04; Y- W- B; Heated oxygen sensor heater operation signal; Ignition switch on; 11 to 14 V. Row 13: E2 6-100, O X 1 B E26-132, E X 1 B; W- R; Heated oxygen sensor signal; Engine speed maintained at 2500 rpm for 2 minutes after warming up engine; Pulse generation, See waveform 4. Row 14: E 26-20, hash 10 –E 26-50, E 01; B- WB; No. 1 fuel injector assembly signal; Ignition switch on; 11 to 14 V. Row 15: E 26-20, hash 10 –E 26-50, E 01; B- W- B; Number 1 fuel injector assembly signal; Idling; Pulse generation, See waveform 5. Back to Figure Row 1: SIL, 7, bus plus line, S signal ground, pulse generation, during transmission. Row 2: CG, 4, chassis ground, body ground, 1 ohms or less, always. Row 3: SG, 5, signal ground, body ground, 1 ohms or less, always. Row 4: BAT, 16, battery positive, body ground, 11 to 14 Volts, always. Row 5: CANH, 6, CAN high line, 14- CANL, 54 to 69 ohms, ignition switch off. Row 6: CANH, 6, CAN high line, battery positive, 6 kilo ohms or higher, ignition switch off. Row 7: CANH, 6, CAN high line, 4-CG, 6 kilo ohms or higher, ignition switch off. Row 8: CANH, 6, CAN high line, 4 - CG, 200 kilo ohms or higher, ignition switch off. Row 9: CANL, 14, CAN low line, battery positive, 6 kilo ohms or higher, ignition switch off. Row 10: CANL, 14, CAN low line, 4-CG, 200 kilo ohms or higher, ignition switch off. Back to Figure Battery, F L main, I G 2 main, ignition switch assembly without smart key

system, number 1 integration relay, certification E C U with smart key E C U assembly, meter I G 2, combination meter assembly, A 25 E C M are labeled. Back to Figure The Inlet filter sock is connected to a Fuel pump on its right. The fuel pump further connects to a Fuel pump control module (PCM) on its right and to a filter placed at 90 degrees. A thin tube connects the filter to four equally spaced port fuel injectors placed in a row above the filter. Two fuel sensors adjacent to each other are placed on the top of the injectors. Back to Figure An illustration shows a fuel indicator. Parts labeled include Replaceable o-rings, Needle valve, Electromagnetic coil, and Filter screen. The shape of the fuel indicator appears roughly rectangular. Two Replaceable o-rings are placed at the extreme left, one in the upper plane and one in the lower. Two Replaceable o-rings are placed at the extreme right, one in the upper plane and one in the lower. A rectangular needle valve is placed between the two o-rings on the left. A U-shaped filter is placed horizontally between the two o-rings on the right. Back to Figure There are two columns. Row data from the TABLE is as follows: Row 1: P0101, Mass or volume air flow circuit range/performance problem. Row 2: P0102, Mass or volume air flow circuit low input. Row 3: P0103, Mass or volume air flow circuit high input. Row 4: P0104, Mass or volume air flow circuit intermittent. Row 5: P0105, Manifold absolute pressure/barometric pressure circuit malfunction. Row 6: P0106, Manifold absolute pressure/barometric pressure circuit range/performance problem. Row 7: P0107, Manifold absolute pressure/barometric pressure circuit low input. Row 8: P0108, Manifold absolute pressure/barometric pressure circuit high input. Row 9: P0109, Manifold absolute pressure/barometric pressure circuit intermittent. Row 10: P0110, Intake air temperature circuit malfunction. Row 11: P0111, Intake air temperature circuit range/performance problem. Row 12: P0112, Intake air temperature circuit low input. Row 13: P0113, Intake air temperature circuit high input. Row 14: P0114, Intake air temperature circuit intermittent. Row 15: P0115, Engine coolant temperature circuit malfunction. Row 16: P0116, Engine coolant temperature circuit range/performance problem. Row 17: P0117, Engine coolant temperature circuit low input. Row 18: P0118, Engine coolant

temperature circuit high input. Row 19: P0119, Engine coolant temperature circuit intermittent. Row 20: P0120, Throttle pedal position sensor/switch a circuit malfunction. Row 21: P0121, Throttle pedal position sensor/switch a circuit range/performance problem. Row 22: P0122, Throttle pedal position sensor/switch a circuit low input. Row 23: P0123, Throttle pedal position sensor/switch a circuit high input. Back to Figure INSPECTION. 1. INSPECT FUEL INJECTOR ASSEMBLY. FIGURE 1: The illustration shows a setup measuring resistance between fuel injector assembly connector terminals. Below the illustration there is a TABLE showing values according to which the resistance is to be measured. There are three columns. Column headers read as: Tester Connection; Condition; Specified Condition. Row against the above headers reads as: 1 to 2, 20 degree Celsius (68 degree Fahrenheit), 11.6 to 12.4 ohm. Footnote reads as If the result is not as specified, replace the fuel injector assembly. b. Inspect the injector injection. X WARNING: Keep the injector away from spark during the test. Back to Figure The A screenshot displays the following title: DISCONNECT WIRE HARNESS. Illustration below the title is labeled as: Locating Fuel Injector Connectors, Bolt and wire harness brackets. Footnotes below the illustration reads as: a. Disconnect the 4 fuel injector connectors. b. Disconnect the 3 connectors. c. Remove the 2 bolts and 2 wires harness brackets. d. Detach the 2 clamps to disconnect the wire harness. 16. REMOVE VACUUM SWITCHING VALVE ASSEMBLY (FOR ACIS). Refer to REMOVAL - STEP 4. 17. REMOVE FUEL DELIVERY PIPE SUB-ASSEMBLY. Back to Figure The diagram includes the fuel pump and fuel injector circuits. The diagram identifies differently highlighted wires, pin and connector numbers, source voltage wiring, ground points, and current paths. Four injectors labeled as #2, #4, #3, #1 are shown placed in a row. Back to Figure The circuit diagram consists of four fuel injector assembly, E C M, integration

relay, ignition switch assembly, smart key E C U assembly, and battery. Back to Figure The path from the battery source voltage to the fuel pump and components used along including fuses, relays, and a fuel pump control module, the fuel pump circuit grounds, including the fuel pump and relays are all highlighted differently. Back to Figure A screenshot of a digital storage oscilloscope displaying the following: Horizontal axis (X) represents time. Axis values are: minus 2.0, 0, 2.0, 4.0, 6.0, 8.0, 10.0, 12.0, 14.0, 16.0, and 18.0. (x 2.0 millisecond). Vertical axis (Y) represents axis voltage. Axis values are: minus 10.0, 0.0, 10.0, 20.0, 30.0, 40.0, 50.0, 60.0, 70.0, 80.0, 90.0. (v). The voltage scale is set to 10 volt/division and the time scale is set to 1 millisecond/division. The line graph starts at 14.0 on the Y axis runs flat until 0.0 on the X axis. The line drops to 0.0. on the Y axis and X axis, runs flat until 4.2 on the X axis. There is a sharp peak at 4.2 on X axis, 87 on Y axis which drops to 5 on X axis and at 14 on the Y axis and remains flat thereafter. Back to Figure The oscilloscope line remains flat at the beginning followed by two sharp narrow troughs parallel to each other and remains flat thereafter. Back to Figure 1. Rear view photo shows a man working on a computer displaying an illustration of ENGINE FUEL SYSTEM (2AR-FE) (SERVICE INFORMATION) (EXCEPT HYBRID). Back to Figure 2. Close up photo shows a gloved hand inspecting fuel injectors and fuel rail of a vehicle. 3. Close up photo shows a gloved hand noting the temperature and comparing the specifications. 4. Close up photo shows a gloved hand installing the circular noid light into the injector connector. Back to Figure

5. The screen of a digital storage oscilloscope displaying the following: Horizontal axis (X) represents time. Axis values are: minus 2.0, 0, 2.0, 4.0, 6.0, 8.0, 10.0, 12.0, 14.0, 16.0, and 18.0. (x 2.0 millisecond). Vertical axis (Y) represents axis voltage. Axis values are minus 10.0, 0.0, 10.0, 20.0, 30.0, 40.0, 50.0, 60.0, 70.0, 80.0, 90.0 (volt). The voltage scale is set to 10 volt/division and the time scale is set to 1 millisecond/division. The line graph starts at 14.0 on the Y axis runs flat until 0.0 on the X axis. The line drops to 0.0 on the Y axis and X axis, runs flat until 4.2 on the X axis. This portion is labeled as ON time. There is a sharp peak at 4.2 on X axis, 87 on Y axis which drops to 5 on X axis and at 14 on the Y axis and remains flat thereafter. Back to Figure 6. A screenshot shows the screen of ALLDATA MANAGE online’s work tab. Headers displayed on the screen are Mileage IN, Mileage OUT, 92174 Confirm, symptoms and DTCs, Add Job group. Code, description, sell, Qty, Discpercent, Taxpercent, Total plus Tax, Actions, Work description, Add, Save as, clear, Predefined work descriptions, Selected work descriptions. Back to Figure 3. Close up photo shows the service port. 4. Close up photo shows fuel gauge attached to the service port. 5. Close up photo shows fuel gauge attached to the service port. 6. Close up photo shows the reinstalled Schrader valve cap. Back to Figure Diagram shows a voltage dividing thermistor circuit connecting E47 Engine coolant temperature sensor on the left with E26 ECM on the right. 5 Volts is shared between a resistor (R) inside the E26 ECM and the thermistor inside the temperature sensor. Back to Figure a) A photo shows a digital multimeter measuring voltage with the harness connected to the sensor. b) A photo shows a digital multimeter while the harness is disconnected. c) A photo shows a gloved hand holding wires next to a monitor screen. d) Photo shows gloved hands holding test probes of the digital multimeter placed on the left.

Back to Figure The first circuit diagram shows input data provided by the Accelerator pedal position sensor to the ECM unit. The accelerator pedal position sensor comprises magnet, IC No. 1, IC No. 2, and another magnet one below the other, respectively. Various input data running parallel one below the other are labeled as VPA, EPA, VCPA, VPA2, EPA2, VCP2, respectively. The above diagram is followed by a graph. The horizontal axis represents the Accelerator Pedal Angle (*). The useable range marked on the graph is from 0 to 13.1. The vertical axis represents Accelerator Pedal Position Sensor Output Voltage (V). Values marked on the vertical axis are: 4.55, 3.988, 3.75, 3.188, 1.6, and 0.8 from top to bottom. Dotted lines run from each of the values parallel. Vertical axis is marked as *1 and indicates Accelerator pedal fully released. A dotted line marked as *2 runs perpendicular at to the horizontal axis at 13.1 and indicates Accelerator pedal fully depressed. Line graph representing VPA2 starts at 1.6 on the vertical axis runs flats at the beginning, slopes upward to intersect *2 and then runs flat corresponding to the dotted line at 4.55. Line graph representing VPA starts at 0.8 on the vertical axis runs flats at the beginning and then slopes upward to intersect *2 and then runs flat corresponding to the dotted line at 3.75. A dotted line running upward from 0.29 on the horizontal axis intersects VPA2 AND VPA. Back to Figure The first circuit diagram shows an analog circuit. Labels marked on the circuit include: Usable Moveable, Moveable Usable range for both *1: Accelerator pedal released (20 degree) and *2: Accelerator pedal depressed (about 110 degree), EP2, VPA2, VCP2, CP1, VPA1, VCP1. The above diagram is followed by a graph. The horizontal axis represents the Accelerator Pedal Angle (degree). The useable range marked on the graph between 0 and 125. The vertical axis represents Accelerator Pedal Position Sensor Output Voltage (V). Values marked on the vertical axis are 5, 1.0, 0.8, and 0 from top to bottom. Two parallel dotted lines run perpendicular to the horizontal axis and as marked as *1: Accelerator pedal released (20 degree) and *2: Accelerator pedal depressed (about 110 degree), respectively. Line graph representing VPA2 starts at 0.8 on the vertical axis slopes upward to intersect *2 and then runs flat to intersect *2. 5. Line graph representing VPA starts at 0 on the vertical axis runs slopes upward to intersect *2. Dotted lines from 1.0 to 0.8 run parallel to intersect 1*.

Back to Figure 1. A photo shows a voltmeter connected to the sensor. The reading displayed on the screen is 0.700. 2. A photo shows a voltmeter connected to the sensor. The reading displayed on the screen is 5.142. 3. A photo shows a voltmeter connected to the sensor. The reading displayed on the screen is 0.004. 4. A photo shows a voltmeter connected to the sensor. The reading displayed on the screen is 0.700. Back to Figure The diagram shows a square with an opening on the lower side. An upward arrow on the opening indicates the direction of the Manifold pressure. The sensor is horizontally divided into two chambers by a Silicon diaphragm. The lower chamber with the opening is labeled as open chamber while the upper chamber is labeled as Sealed (vacuum) chamber. Back to Figure The contents are as follows: 2011 Toyota Avalon 3.5L Eng Limited. DTC P0102: Mass Or Volume Air Flow Circuit Low Input (TO 12/2010): DTC P0103: Mass Or Volume Air flow circuit high input. (TO 12/2010). Further details are given under titles DESCRIPTION AND HINT. The above is followed by FIGURE 1 titled as Identifying Mass Air Flow Circuit Diagram. Back to Figure The diagram has two parts. The upper part is labeled as G94E31744. The diagram shows the following parts: Screen, Hot wire sensor, Cold wire sensor, and arrows indicating air flow. A hot wire is located in part of the intake airflow between the air filter and the throttle body. The hot wire is part of a bridge circuit. The bridge circuit has four loads: the platinum hot wire, a thermistor, and two fixed value resistors. The bridge circuit uses battery source voltage. A rightward arrow from point B on the hot platinum wire indicates the output voltage. Back to Figure There are two separate diagrams. 1. Parts labeled include: Vortex generator, Pressure directing hole, Karman vortex, Mirror, LED, Photo transistor. The air

entering the sensor passes over a vortex generator, which causes the airflow to tumble. This creates pressure pulses that are detected using an LED and photo diode. 2. Parts labeled include: Mirror, Photocoupler, Pressure directing hole, Intake air temperature sensor. An arrow pointing toward the sensor reads as: From air cleaner. An arrow emerging from the right end of the sensor reads as: To intake chamber. Back to Figure The wave form is flat at the beginning, then drops straight downward, then shows a sharp tall peak which further drops and continues flat till the end of the graph. Content displayed left to the vertical axis reads as Example waveform, Recall, Run, Save, Cursor, Time/Div 2 milliseconds. Content displayed below the horizontal axis reads as Ch 1: 20.00 V DC, Ch 3: OFF, Ch 2: OFF, Ch 4: OFF, Review Questions 79: Level: 100.00V, Nrml; Source: Ch1, Rising edge. Back to Figure Circuit diagram shows three components: 1. Body Control Module (BCM) comprising a fuel pump fuse 15 A, Fuel Pump relay. Ground distribution schematics in wiring systems and Power distribution schematics in wiring systems are highlighted. 2. Powertrain Control Module (PCM) comprising fuel pump relay control. 3. Fuel pump and sender assembly comprising fuel pump (2BK). Back to Figure The horizontal axis is labeled time in millisecond ranging from -3 to 7. The vertical axis on the left is labeled voltage ranging from -10 to 90. The vertical axis on the right is labeled current ranging from 0.9 to 1.8. The waveform is flat at the beginning, then drops straight downward, then shows a sharp tall peak which further drops and continues flat till the end of the graph. The text under the graph reads waiting for ADC, trigger, repeat, Ch A, falling, 8 V, -30 percentage. Back to Figure Part labels are as follows: Tachometer/ fuel economy gauge, Main relay, Diagnostic 14 connector, Battery 6 BK junction block, Fuel pump relay, Fusible link A, Battery, Power distribution box, Main fuel pump, and a Motronic control

unit. The Motronic control unit comprising Main relay control, Power input, Present fuel rate output, Fuel pump relay control in solid state. Back to Figure In the center is the injector, which is a tubelike structure, narrowed down to a nozzle from which the liquid is flowing out. To its one side is a tubelike structure labeled valve. On the other side of it is a spark plug. An arrow passing through it shows the direction of the pressure. Back to Figure The components of the lift fuel pump are as follows: Direct injector, highpressure fuel sensor, fuel rail, high-pressure fuel pump, low-pressure fuel sensor, fuel pressure regulator valve, fuel filter, and low-pressure fuel pump. Back to Figure It is a cylindrical structure. An outlet on the top leading to a smaller cylindrical structure with horizontal lines over it is labeled as piezo stack. It is connected to an injector piston. This further narrows down and is followed by injector valve. Narrow tubes from it connect to the injector needle. Alongside this, from the top runs a narrow tube which goes till the needle. It is labeled as fuel supply. Along the fuel supply tube runs another tube with an outlet toward the side, labeled as leak back. This connects right above the injector valve. Back to Figure A small cylindrical structure is labeled, High-pressure fuel pump. On its side is a small tube; labeled as Electric pressure control valve. On the other side of the fuel pump is a horizontally elongated pipelike structure labeled as fuel rail. Toward the end, on the top, a small button is labeled as fuel pressure sensor. Toward the bottom of the fuel rail are four similar tubelike structures, and the fourth one placed right below the fuel pressure sensor is labeled as fuel injector. Back to Figure The first image shows the injection with the seal intact. An inset shows a close up view of the back side. The second image shows the seal moved from its place and being removed. An inset shows the seal retaining area intact.

Back to Figure There are four columns: Operation State, strategy, objective, effect. The strategy column has an illustration in each row labeled, TDC, EX, IN, and BDC. Row 1: During idling; earliest timing, exhaust and latest timing, intake; eliminating overlap reduces blow back to the intake side; Stabilized idling engine speed, Better fuel economy. Row 2: At light load; exhaust to advanced side and intake at retard side; eliminating overlap to reduce blow back to the intake side; ensured engine stability. Row 3: At medium load; exhaust to advance side and intake to retard side; increasing overlap increases internal EGR, reducing pumping losses; Better fuel economy, improved emission control. Row 4: In low- to medium-speed range with heavy load; exhaust to retard side and intake to advance side; advancing the intake valve closing timing improves volumetric efficiency; improved torque in low to medium speed ranges. Row 5: In high-speed range with heavy load; intake to retard side and exhaust to advance side; Retarding the intake valve closing timing improves volumetric efficiency; improved output. Row 6: At low temperatures; earliest timing, exhaust and latest timing, intake; Eliminating overlap to reduce blow back to the intake side stabilizes the idling speed at fast idle; Stabilized fast idle engine speed, better fuel economy. Row 7: Upon starting, stopping engine; earliest timing, exhaust and latest timing, intake; eliminating overlap minimizes blow back to the intake side; Improved startability. Back to Figure The injector is in the center and has two structures with springs on its either side. On one side is a coolant passage. From the nozzle of the injector, the spray is shown. Back to Figure The structure shows a vertical structure which ends in a high-voltage connection, spark plug, or terminal 4. Right above the tube-like structure is a rectangular-shaped structure labeled as mould compound. Within it toward the top is a primary coil. The primary coil is connected to a magnetic core above it. This further has a secondary coil on it which produces 12 volts of current. Back to Figure A battery, ignition switch with start and run, CCRM, Ignition module,

tachometer, CKP sensor, camshaft sprocket, trigger wheel are labeled. Back to Figure It displays duration time of the spark, and other data about spark voltage. There are five keys below the screen. Back to Figure The first spark plug in image A is shining, and slightly brown in color. The second image B appears all black, with its tip rusted. Back to Figure The column entries are as follows. Symptoms, Causes, and Remedy. The row entries are as follows. Row 1: Hard starting, misfiring, and black exhaust smoke; an image shows a fully blackened tip of a spark plug titled as carbon fouled. Rich mixture, Retarded ignition, Low compression, and Too cold a spark plug; Check float level, Check choke, Check ignition timing, Check air cleaner, Check compression, and Replace spark plug with correct heat range. Row 2: hard starting, misfiring, gray or white exhaust smoke, and loss of oil; an image of an oil fouled spark plug has slight black particles over it. Worn rings, Worn piston, Leaking valve stem seals, and Over-filled oil sump; Replace worn components, and Replace spark plug with correct heat range. Row 3: ‘’Pinking’’ under acceleration or climbing hills, and Engine run-on after switching off; an image shows a light collared spark plug. Lean mixture, Advanced ignition timing, and Too hot a spark plug; Check jets are not clogged, Check float level, Check ignition timing, and Replace spark plug with correct heat range. Row 4: Misfiring, Loss of power, Hard starting, and Noise in engine; an image shows a damaged spark plug. Foreign particles inside cylinder, and Broken or damaged valve; Replace spark plugs, and Remove foreign or damaged components. Row 5: Melted spark plug, damaged piston crown, and Damage to cylinder head; an image shows a pre-ignition damage in the spark plug. Ignition system failure, Incorrect fuel, and Carbon build-up on the head of the piston; Replace spark plugs, Tighten spark plug to correct torque, Replace damaged components, and Check compression on all cylinders. Row 6: Reddish brown stain above metal shell on insulator; an image shows a spark plug with a reddish brown color on it. It is the corona stain; Oil particles suspended in the air adhere to the insulator due to high voltage; No deterioration to the function of the spark plug, and Change spark plug ONLY at recommended service intervals.

Back to Figure Following is the information on the page. Plug wire, 1991 Volkswagen GTI 1.8 L Eng. High tension wire resistance. Application; Ohms. Vanagon - coil wire with connectors: 1200 to 2800. Spark plug wire or connector: 4600 to 7400. Spark plug connector: 4000 to 6000. Suppressor: 600 to 1400. Except Venison - coil wire only: dot. Coil wire with connector: 1600 to 2400. Spark plug wire or connector: 4000 to 6000. Suppressor: 600 to 1400. Suppressor is located between ignition wire and distributor cap. Check for continuity. Back to Figure On the top is the area with sensors, which is labeled as connector or wire. It is a Connection to the car connection. A little below it is an electric circuit. It transmits the electrical signal from the hall sensor to the terminals protecting against possible peak voltages. Next to it is a round ring-like structure labeled as metal fitting. It is anchored to the car. The extra layer toward the outside of the ring is labeled as Overmolded Plastic Casing. At the bottom of the crankshaft below the circuit is a semiconductor chip with a hall sensor on its side. Back to Figure A TABLE has following column entries. Name, value, range, and unit. The row entries are as follows. Row 1: dollar 7E8 calculated load value; 0; 0…100; percentage. Row 2: dollar 7E8 engine RPM; 0; 0…16383.75; revolutions per minute. Row 3: dollar 7E8 vehicle speed sensor; 0; 0...255; kilometer per hour. Back to Figure The horizontal axis shows the time in millisecond ranging from 0 to 200 with an equal interval of 20. The vertical axis shows the voltage V ranging from negative 20 to 20 in equal interval of 4. The graph plotted lies uniformly between negative 4 to 4 of voltage. Back to Figure One wire is connected to the ground and another to the signal wire. An inset square wave signal with the 0 Volt and positive 5 Volt is shown. Accompanying text reads, ECM triggers on rising edge of signal corresponding to edge of tooth

moving away from sensor centerline Signal. Back to Figure Labeled as follows: VVT sensor, bank 2 intake side, front of left cylinder bank; VVT sensor, bank 1 exhaust side, rear of right cylinder bank; VVT sensor, bank 2 exhaust side, rear of left cylinder bank; VVT sensor, bank 1 intake side, front of right cylinder bank. There are three colored signals arising from each sensor. Back to Figure The first signal has regular square waves, alternating constant waves above and on the baseline. The second signal shows a single square wave below the baseline and a flat line. Back to Figure A wide almost rectangular structure at the bottom has a dark color at the base, labeled as Color coded mixture. In it lies the connecting rod, which in turn is connected to a piston placed above it. The region where the piston is placed is slightly narrower than the part below. It is surrounded by a cylinder wall on either side. Right above the piston in the center is a spark plug with valves on the either side. Back to Figure They read as follows: DIAGNOSTIC INFORMATION AND PROCEDURES > DTC P0351–0356, P2300, P2301, P2303, P2304, P2306, P2307, P2309, P2310, P2312, P2313, P2315, OR P2316: IGNITION COIL > CIRCUIT/SYSTEM TESTING. 1. Ignition OFF and all vehicle systems OFF, disconnect the harness connector at the appropriate T8 Ignition Coil. It may take up to 2 minutes for all vehicle systems to power down. Back to Figure It reads as follows: 2014 Ford Focus 2.0L L4 direct gas injection. Genetic OBD II Freeze EUC ID. The column headings are EUC ID in dollars and E8. P0353 ignition coil primary or secondary circuit. Row 1: engine speed: 952. Row 2: absolute throttle position in percentage: 11.4. Row 3: absolute throttle position in percentage B: 11.8. Row 4: relative throttle position: 2.7. Row 5: commanded throttle act control: 3.5.

Back to Figure Following is the text on the screen. 2010 Toyota Camry 3.5L Eng SE. When the engine misfires, high concentrations of hydrocarbons enter the exhaust gas. High hydrocarbons concentration levels can cause increase in exhaust emission levels. Extremely high concentrations of hydrocarbons can also cause increases in the three-way catalytic converter temperature, which may cause damage to the three-way catalytic converter. To prevent this increase in emissions and to limit the possibility of thermal damage, the ECM monitors the misfire rate. When the temperature of the three way catalytic converter reaches the point of thermal degradation, the ECM blinks the MIL. To monitor misfires, the ECM uses both the VVT sensor and the crankshaft position sensor, The VVT sensor is used to identify any misfiring cylinders and the crankshaft position sensor is used to measure variations in the crankshaft rotation speed, and Misfires are counted when the crankshaft rotation speed variations exceed predetermined thresholds. If the misfire count exceeds the threshold levels, the ECM illuminates the MIL and sets a DTC. OTC NO, P0300 P0301 pog02 P0304 POJ05 OTC Detection condition Simultaneous misfiring of several cylinders occurs and CHte of following conditions below is detected, 2 trip detection logic: High temperature misfire occurs in three way catalytic converter, MIL blinks. Emission deterioration misfire occurs, MIL illuminates. Misfiring of specific cylinder occurs and one of following conditions below detected, 2 trip logic: High temperature misfire occurs in three way catalytic converter, MIL blinks. Emission deterioration misfire occurs, MIL illuminates Trouble Area, Open or short in engine Wire harness, Connector connection, Vacuum hose. Back to Figure The column entries are description, MID, TID, Min, Max, value, unit, and result. The row entries are as follows: Row 1: not applicable for SAE J1850, ISO 91412 and 14230-2; A5; 0B; 0; 65535; 36; counts; ok. Row 2: not applicable for SAE J1850, ISO 9141-2 and 14230-2; A5; 0C; 0; 65535; 0; counts; OK. Row 3: cylinder 4 and catalyst damage misfire rate; A5; 80; 0.00; 31.00; 0.00; percentage; OK. Row 4: cylinder 4 and emission threshold misfire rate; A5; 81; 0.00; 1.00; 16.25; percentage; failed. Connections, Ignition system, Injector, Mass air flow meter, Engine coolant temperature sensor, Compression pressure, Valve clearance, Valve timing. Back to Figure

The entries are as follows. diagnostic trouble count code: 1. Cylinder 1 average misfires last 10 drive cycles: 0. Cylinder 1 misfires current drive cycles: 0. Cylinder 2 average misfires last 10 drive cycles: 0. Cylinder 2 misfires current drive cycles: 2. Cylinder 3 average misfires last 10 drive cycles: 0. Cylinder 3 misfires current drive cycles: 0. Cylinder 4 average misfires last 10 drive cycles: 0. Back to Figure Engine immobilizer system, w or smart key system. Engine immobilizer system, with respect to smart key system. VC output circuit, ECM 5 Volts output. ECM power source circuit. Crankshaft position sensor. Valve timing. Camshaft position sensor, for intake camshaft. Camshaft position sensor, for exhaust camshaft. Ignition system. Fuel pump control circuit. Fuel injector circuit. Starter signal circuit. Back to Figure The column entries are, name, value, range, and unit. The row entries are, row 1: dollar 7E8 engine coolant temperature; 34; 0…130; degree Celsius. Row 2: dollar 7E8 intake air temperature; 38; negative 40…215; degree Celsius. Back to Figure The horizontal axis is labeled ms ranging from 0 to 200. The vertical axis on the left is labeled plus or minus 10 volt ranging from -4 to 10. The vertical axis on the right is labeled plus or minus 10 volt ranging from -10 to 10. Crankshaft sensor shows the square waveform pattern. The camshaft sensor shows the linear waveform pattern. Back to Figure Engine immobilizer system, with respect to smart key system. VC output circuit, ECM 5 V output. ECM power source circuit. Crankshaft position sensor. Valve timing. Camshaft position sensor, for intake camshaft. Camshaft position sensor, for exhaust camshaft. Ignition system. Fuel pump control circuit. Fuel injector circuit. Starter signal circuit. 2010 Toyota Camry 3.5L Eng SE. The ECM illuminates the MIL and sets a DTC when either one of the following conditions, which could cause emission deterioration, is detected, 2 trip detection logic. Within the first 1000 crankshaft revolutions Of the engine

starting, an excessive misfiring rate, approximately 20 to 50 misfires per 1000 crankshaft revolutions occurs once. An excessive misfiring rate, approximately 20 to 50 misfires per 1000 crankshaft revolutions occurs a total of 4 times. The ECM flashes the MIL and sets a DTC when either one of the following conditions, which could cause the three way catalytic converter damage, is detected, 2 trip detection logic. At a high engine RPM, a catalyst damage misfire, which monitored every 200 crankshaft revolutions, occurs once. At a normal engine RPM, a catalyst damage misfire, which monitored every 200 crankshaft revolutions, occurs 3 times. HINT: If a catalyst damage misfire occurs, the ECM informs the driver by flashing the MIL. Back to Figure There are three columns: D T C number, D T C condition, and issue location. The data of the TABLE are as follows: D T C Number: P0300. D T C condition: Several cylinders misfire simultaneously. One of the following conditions is met (two-trip detection logic): Misfire that could damage the three-way catalytic converter. Misfire signaling emission deterioration. D T C number: P0301, P0302, P0303, P0304. DTC condition: Specific cylinder misfires. One of the following conditions is met (two-trip detection logic): Misfire that could damage the three-way catalytic converter. Misfire signaling emission deterioration. Issue location: Engine wire harness. Connector connection. Vacuum hose connection. Ignition system. Fuel injector assembly. Fuel pressure. Mass airflow meter subassembly. Engine coolant temperature sensor. Compression pressure. Valve timing. Positive crankcase ventilation. Intake system. Intake air control valve actuator. Engine control module. Back to Figure A square with ECM on it is connected by an arrow IGT to ignition coil assembly. From it, another arrow IGF connects to ECM. The ignition coil assembly box has a square, igniter, and a rectangle ignition coil. The ignition signal shows a uniform signal. Below it is normal signal which has a slightly different but uniform signal. It is followed by a malfunction circuit open which is not uniform. Back to Figure The horizontal axis shows 20 millisecond per DIV. The vertical axis shows the 5 Volts per DIV. The uniform signal is formed horizontally across The graph.

Back to Figure The lists are as follows: Compression, Ignites system, Spark plug, Fuel injector circuit, ECM power source circuit, Throttle with motor body assembly, Fuel pump control circuit, Fuel pump, Smoke system, Purge VSV, PCV valve and hose, Air fuel ratio sensor, Heated oxygen sensor, Mass air flow meter subassembly, Knock control sensor, External part malfunction, increase in load: A/C system, et cetera. Back to Figure The photo is titled SAE standards documents on OBD-II. The text below it reads: J1962 - Defines the connector used for the OBD-II interface. • J1850 - Defines a serial data protocol. There are 2 kinds - 10.4 kilo bites per second (single wire, VPW) and 41.6 kilo bites per second (2 wire, PWM). Mainly used by US manufacturers, also known as PCI (Chrysler, 10.4K), Class 2 (GM, 10.4K), and SCP (Ford, 41.6K) • J1978 - Defines minimal operating standards for OBD-II scan tools • J1979 - Defines standards for diagnostic test modes • J2ct12 - Defines standards DTCs and definitions. • J2178-1 - Defines standards for network message header formats and physical address assignments • J2178-2 - Gives data parameter definitions • J2178-3 - Defines standards for network message frame IDs for single byte headers • J2178-4 - Defines standards for network messages with three byte headers (asterisk) • J2284-3 - Defines 5pg0K CAN Physical and Data link layer • J2411 - Describes the GMLAN (single-wire CAN) protocol, used in newer GM vehicles. Often accessible on the OBD connector as PIN 1 on newer GM vehicles. Back to Figure The pins labeled on A are: Pin 1 Discretionary; Pin 2 Bus + (plus) JI850; Pin 3 Discretionary Pin 4 Chassis Ground; Pin 5 Signal Ground; Pin 6; Pin 7 K-Line ISO 9141/KWP; Pin 8 Discretionary; Pin 9 Discretionary; Pin 10 Bus – JI850; Pin 11 Discretionary; Pin 12 Discretionary; Pin 13 Discretionary; Pin 14; Pin 15 L-Line ISO 9141/KWP, and Pin 16 Unswitched Battery + (plus). The pins labeled on B are: Pin 1 Discretionary; Pin 2 Bus + (plus) JI850; Pin 3

Discretionary; Pin 4 Chassis Ground; Pin 5 Signal Ground; Pin 6 CAN high; Pin 7 K-Line ISO 9141/KWP; Pin 8 Discretionary; Pin 9 Discretionary; Pin 10 Bus – JI850; Pin 11 Discretionary; Pin 12 Discretionary; Pin 13 Discretionary; Pin 14 CAN low; Pin 15 L-Line ISO 9141/KWP, and Pin 16 Unswitched Battery + (plus). Back to Figure The TABLE is titled SFI system. The TABLE is in the sequence: DTC code then Detection item then MIL then Memory: P0010: Camshaft position “A” actuator circuit (bank 1): Comes on DTC stored; P0011: Camshaft positions “A” - timing over-advanced or system performance (bank 1): Comes on: DTC stored; P0012: Camshaft positions “A” - timing over-retarded (bank 1): Comes on: DTC stored; P0013: Camshaft positions “B” - actuator circuit/open (bank 1): Comes on: DTC stored; P0014: Camshaft positions “B” - timing over-advanced or system performance (bank 1): Comes on: DTC stored; P0015: Camshaft positions “B” - Timing over-retarded (bank 1): Comes on: DTC stored ; P0016: Crankshaft position - camshaft position correlation (bank 1 sensor A): Comes on: DTC stored; P0017: Crankshaft position - camshaft position correlation (bank 1 sensor B): Comes on: DTC stored; P0031: Oxygen (A/F) sensor heater control circuit low (bank 1 sensor 1): Comes on: DTC stored; P0032: Oxygen (A/F) sensor heater control circuit high (bank 1 sensor 1): Comes on: DTC stored; P0037: Oxygen sensor heater control circuit low (bank 1 sensor 2): Comes on: DTC stored; P0038: Oxygen sensor heater control circuit high (bank 1 sensor 2): Comes on: DTC stored; P0101: Mass air flow circuit range/performance problem: Comes on: DTC stored; P0102: Mass air flow circuit low: Comes on: DTC stored; P0103: Mass air flow circuit high: Comes on: DTC stored; P0111 Intake air temperature sensor 1 circuit range/performance: Comes on: DTC stored. Back to Figure The illustration is titled explanation of OBD2 Diagnostic Trouble Codes. Below it are five cross signs such that three are clubbed on the left and two are clubbed on the right. The first cross reads: B - Body (include A/C and air bag); C Chassis (include ABS); P - Powertrain (Engine and transmission/gearbox) and U - User network (wiring bus/UART), the second cross reads: 0 - Generic OBO Code and 1 - Vehicle manufacturer specific code, the third cross reads: 1 - Fuel and air metering; 2 - Fuel and air metering (injector circuit); 3 - Ignition system

or misfire; 4 - Auxiliary emission controls; 5 - Vehicle speed control and idle control system; 6 - Computer output circuit; 7, 8, 9 - Transmission (gearbox) and A, B, C - For hybrid propulsion, and the last two crosses read: fault description. Back to Figure On top is a box labeled engine control module. The points labeled on its upper end are 7A AC1, 6A ACT, 15D TAC; 23D IGT1, 17D IGF and 22D IGT2 and the points labeled on the lower end are: 4D IDLO, 10C VTA, 1C VCC, 10R PTNK, 7D RSO, 6D RSC, 15C EGR, 12C KNK, 7C TE1, 5C OX1 and 2D HT1. Next in the row are cruise control ECU, T1 throttle position sensor, V8 vapor pressure, I1 Idle air control valve, V3 VSV (EGR), K1 knock sensor 1, D1 data link connector 1 and H3 heated oxygen sensor (Bank 1 sensor 1). Back to Figure The headers are: Binary; Decimal; Hexadecimal: Row 1: 0; 0; 0; Row 2: 1; 1; 1; Row 3: 10; 2; 2; Row 4: 11; 3; 3; Row 4: 100; 4; 4; Row 5: 105; 5; 5; Row 6: 110; 6; 6; Row 7; 111; 7; 7; Row 8: 1000; 8; 8; Row 9: 1001; 9; 9; Row 10: 1010; 10; A; Row 11: 1011; 11; B; Row 12: 1100; 12; C; Row 13: 1101; 13; D; Row 14: 1110; 14; E; Row 15: 1111; 15; F; Row 16: 10000; 16; 10; Row 17: 10001; 17; 11; Row 18: etc.; etc; etc. Back to Figure The text on the TABLE reads: Typical EGR hose check malfunction thresholds: DPFE sensor voltage: is less than 7 inches of water, is greater than 7 inches of water; 979 Mode Dollar 06 Data; The headers are: Test ID: Comp id: Description: Units: Row 1: Dollar 41: Dollar 11: Delta pressure for upstream hose test and threshold: inches of water; Row 2: Dollar 41: Dollar 12: Delta pressure for downstream hose test and threshold: inches of water; Conversion for Test ID Dollar 41: If value is greater than 32.767, the value is negative. Take value, subtract 65.536, and then multiply result by 0.0078 to get inches of water. If value is less than or equal to 32.767, the value is positive. Multiply by 0.0078 to get inches of water. Back to Figure The TABLE has no header: Row 1: Control the injection volume for A/F sensor:

Change injection volume; minus 12.5 percent /0 percent /12.5 percent; All fuel injector assemblies are tested at the same time. • Perform the test at 300 rpm or less.• Control the injection volume for A/F sensor enables the checking and graphing of the air fuel ratio sensor and heated oxygen sensor voltage outputs.• To conduct the test, enter the following menus: powertrain/ engine and ECT/active test/control the injection volume for A/F sensor/gas AF control/AFS voltage B151 and O25 B152.• During the active test, air fuel ratio feedback control and feedback learning are stopped; Row 2: Activate the VSV for intake control: Activate vacuum switching valve (for acoustic control induction system); ON/OFF; • ON: Acoustic control induction system VSV is on.• OFF: Acoustic control induction system VSV is off.• This test can only be operated for 10 seconds.; Row 3: Activate the VSV for EVAP control: Activate purge VSV control; ON/OFF; • The purge VSV is opened with a 3ct percent duty ratio.• See waveform (asterisk)5; Row 4: Control the fuel pump/speed: Activate fuel pump; ON/OFF; Perform this test when the following conditions are met:• Ignition switch is ON.• Engine is stopped.• Shift level in P. Back to Figure A screenshot shows the scan tool Mode 9 displays the vehicle VIN and, for some vehicles, the PCM (Pulse Code Modulation) hardware and software calibration data. Back to Figure The labeled pins are as follows: 1 - Manufacturers Discretion; 2 - SAE J1850 Bus +; 3 - Manufacturers Discretion; 4 - Chassis Ground; 5 - Sensor Ground; 6 SAE J2284 CAN High; 7 - ISO 9141-2 K Line; 8 - Manufacturers Discretion; 9 Manufacturers Discretion; 10 - SAE J1850 Bus -; 11 - Manufacturers Discretion; 12 - Manufacturers Discretion; 13 - Manufacturers Discretion; 14 - SAE J2284 CAN Low; 15 - ISO 9141-2 L Line; 16 - Manufacturers Discretion. Back to Figure On top is a 16 Pin terminal from DLC. The boxes are numbered from 1 to 16 and are labeled as follows: 4. battery negative; 5. ground distribution junction box and 16. Fuse. Fuse is indicated as battery positive and further points at power distribution junction box. Below it are four boxes: ISO labeled Park

module; UBP labeled Temp module; UBP labeled Security module and UBP labeled Driver seat module. Below them are 4 boxes: ISO labeled SRS module; ABS module with Can bus negative and positive terminals; PCM module with FEPS, can bus positive and negative terminals; Cluster module with UBP, can bus negative and positive terminals. Back to Figure The brand names shown are: Demo, Ford, BMW, GM, Chrysler, Dodge, Jeep, Aston Martin, Maserati, Volvo, and Renault. Back to Figure The text reads: Description: A thermistor, whose resistance value varies according to the engine coolant temperature, is built into the engine coolant temperature sensor. The structure of the sensor and its connection to the ECM are the same as those of the intake air temperature sensor. Hint When DTC P0115, P0117, or P0118 is stored, the ECM enters fail-safe mode. During failsafe mode, the engine coolant temperature is estimated to be 80 degree Celsius (176 degree Fahrenheit) by the ECM. Fail-safe mode continues until a pass condition is detected. The headers are: DTC No.; Detection Condition; Trouble Area; Row 1: P0115: An open or short in the engine coolant temperature sensor circuit for 0.5 seconds (1 trip detection logic): • Open or short in engine coolant temperature sensor circuit• Engine coolant temperature sensor• ECM. Row 2: P0117: A short in the engine coolant temperature sensor circuit for 0.5 seconds (1 trip detection logic): Short in engine coolant temperature sensor circuit• Engine coolant temperature sensor• ECM•. Row 3: P0118: An open in the engine coolant temperature sensor circuit for 0.5 seconds (1 trip detection logic): • Open in engine coolant temperature sensor circuit• Engine coolant temperature sensor• ECM. Hint: When any of these DTCs are output, check the engine coolant temperature using the Techstream. Enter the following menus: Powertrain / Engine and ECT / Data list / Primary / Coolant temp. The headers are: Temperature Displayed: Malfunction; Row 1: 40 degree Celsius (minus 40 degree Fahrenheit: Open circuit; Row 2: Higher than 135 degree Celsius (275 degree Fahrenheit): Short circuit. Monitor Description: The engine coolant temperature sensor is used to monitor the engine coolant temperature. The engine coolant temperature sensor has a thermistor with a resistance that varies according to the temperature of the engine coolant. When the coolant

temperature is low, the resistance in the thermistor increases. When the temperature is high, the resistance drops. These variations in resistance are reflected in the output voltage from the sensor. The ECM monitors the sensor voltage and uses this value to calculate the engine coolant temperature. When the sensor output voltage deviates from the normal operating range, the ECM interprets this as a fault in the engine coolant temperature sensor circuit and stores a DTC. Example: If the sensor output voltage is higher than 4.91 Volt for 0.5 seconds or more, the ECM determines that there is an open in the engine coolant temperature sensor circuit, and stores DTC P0118. Conversely, if the voltage output is less than 0.14 Volt for 0.5 seconds or more, the ECM determines that there is a short in the sensor circuit, and stores DTC P0117. Monitor Strategy: Row1: Related DTCs: P0115: Engine coolant temperature sensor range check (chattering)P0117: Engine coolant temperature sensor range check (low voltage)P0118: Engine coolant temperature sensor range check (high voltage); Row 2: Required sensors/components (main): Engine coolant temperature sensor; Row 3: Required sensors/components (related); Row 4: Frequency of operation: Continuous; Duration: 0.5 seconds; Row 5: MIL operation: Immediate; Row 6: Sequence of f operation: None. Back to Figure The text reads: Description: A thermistor, whose resistance value varies according to the engine coolant temperature, is built into the engine coolant temperature sensor. The structure of the sensor and its connection to the ECM are the same as those of the intake air temperature sensor. Hint When DTC P0115, P0117, or P0118 is stored, the ECM enters fail-safe mode. During failsafe mode, the engine coolant temperature is estimated to be 80 degree Celsius (176 degree Fahrenheit) by the ECM. Fail-safe mode continues until a pass condition is detected. The headers are: DTC No.; Detection Condition; Trouble Area; Row 1: P0115: An open or short in the engine coolant temperature sensor circuit for 0.5 seconds (1 trip detection logic): • Open or short in engine coolant temperature sensor circuit• Engine coolant temperature sensor• ECM. Row 2: P0117: A short in the engine coolant temperature sensor circuit for 0.5 seconds (1 trip detection logic): Short in engine coolant temperature sensor circuit• Engine coolant temperature sensor• ECM•. Row 3: P0118: An open in the engine coolant temperature sensor circuit for 0.5 seconds (1 trip detection logic): • Open in engine coolant temperature sensor circuit• Engine coolant temperature sensor• ECM.

Back to Figure Description: Hint: This DTC relates to the thermostat. This DTC is stored when the engine coolant temperature does not reach 75 degree Celsius (176 degree Fahrenheit) despite sufficient engine warm-up time having elapsed. The headers are: DTC No.; DTDC Detection Condition; Trouble area: Row 1: P0128: All of the following are met for 5 seconds (2 trip detection logic): (a) Cold start. (b) The engine is warmed up. (c) The engine coolant temperature is less than 75 degree Celsius (167 degree Fahrenheit). Monitor description: A line graph with x-axis labeled as time and y-axis labeled as engine coolant temperature. Two lines are labeled estimated engine coolant temperature and Indicated engine coolant temperature reading. A horizontal line is labeled Threshold (75 degree Celsius) and a length on it is labeled 5 seconds. The lower point of a perpendicular line is labeled DTC stored (after 2 driving cycles). The ECM estimates the engine coolant temperature based on the starting temperature, engine loads and engine speeds. The ECM then compares the estimated temperature with the actual engine coolant temperature. When the estimated engine coolant temperature reaches 75 degree Celsius (176 degree Fahrenheit), the ECM checks the actual engine coolant temperature. If the actual engine coolant temperature is less than 75 degree Celsius (176 degree Fahrenheit), the ECM interprets this as a malfunction in the thermostat or the engine cooling system and stores the DTC. Monitor Strategy: Row 1: Related DTCs: P0128: Coolant thermostat; Row 2: Required sensors/components (main): Thermostat, Engine coolant temperature sensor; Row 3: Required sensors/components (related): Intake air temperature sensor, Vehicle speed sensor; Row 4: Frequency of operation: Once per driving cycle; Row 5 Duration: 690 seconds; Row 6: MIL operation: 2 driving cycles; Row 7: Sequence of operation: None. Back to Figure The text in the photo reads: Typical Enabling Conditions: Monitor runs whenever the following DTCs are not stored: None. Back to Figure The text reads: Row 1: Monitor runs whenever the following DTCs are not stored : P0010 (VVT oil control valve), P0011 (VVT system - advance), P0012 (VVT system - retard), P0013 (Exhaust VVT oil control valve), P0014 (Exhaust VVT system - advance), P0015 (Exhaust VVT system - retard), P0016 (VVT

system - misalignment), P0017 (Exhaust VVT system - misalignment), P0031, P0032, P0101D (Air fuel ratio sensor heater), P0102, P0103 (Mass air flow meter), P0112, P0113 (Intake air temperature sensor), P0115, P0117, P0118 (Engine coolant temperature sensor), P0120, P0121, P0122, P0123, P0220, P0222, P0223, P2135 (Throttle position sensor), P014C, P041D, P015A, P015B, P2195, P2196, P2237, P2238, P2239, P2252, P2253 (Air fuel ratio sensor), P0171, P0172 (Fuel system), P0300 - P0304 (Misfire)P0335 (Crankshaft position sensor), P0340, P0342, P0343 (Camshaft position sensor), P0351 - P0354 (Igniter), P0365, P0367, P0368 (Exhaust camshaft position sensor), P0500 (Vehicle speed sensor), P219A, P219C, P219D, P219E, P219F (Air fuel ratio imbalance); Row 2: Battery voltage: 11 Volt higher ; Row 3: Either of the following conditions are met: 1 or 2; 1. Row 4: All of the following conditions are met: (a), (b) and (c; Row 5: ( a) Engine coolant temperature at engine start - Intake air temperature at engine start: ¬15 to 7 degree Celsius (¬27 to 12.6 degree Fahrenheit ); Row 6: (b) Engine coolant temperature at engine start): ¬10 to 56 degree Celsius (14 to 133 degree Fahrenheit ); Row 7: (c) Intake air temperature at engine start: ¬10 to 56 degree Celsius (14 to 133 degree Fahrenheit ); Row 8: 2. All of the following conditions are met: (d), (e) and (f); Row 9: d) Engine coolant temperature at engine start - Intake air temperature at engine start: Higher than 7 degree Celsius (12.6 degree Fahrenheit ) Row 10: (e) Engine coolant temperature at engine start: f 56 degree Celsius (133 degree Fahrenheit ) or less; Row 11: (f) Intake air temperature at engine start: 10 degree Celsius (14 degree Fahrenheit) or higher; Row 12: Accumulated time that vehicle speed is 128 kilometer per hour (80 meter per hour) or more¬: Less than 20 seconds. Back to Figure The text on the top reads: Wiring diagram. Next to it is a box with two terminals THW 2 and E2 1 labeled as E47 Engine coolant temperature sensor. And a box next to has terminals THW 95 connected to R and then to 5v and ETHW 96 labeled E26 ECM. Back to Figure Text on the top reads: a) Disconnect the engine coolant temperature sensor connector. Below it are two boxes that have terminals THW and E2 and terminals THW and ETHW. The two boxes are labeled 1 and 2 respectively. Next to them is an oval with the text: E47 next is digital watch-like box with 1

and 2 labeled as E2 and THW respectively. The text below read:(b) Connect terminals 1 (E2) and 2 (THW) of the engine coolant temperature sensor connector on the wire harness side; (c) Connect the Techstream to the DLC3; (d) Turn the ignition switch to ON; (e) Turn the Techstream on; (f) Enter the following menus: Powertrain / Engine and ECT / Data list / Primary / Coolant Temp and (g) Read the value displayed on the Techstream. Standard value: Higher than 135 degree Celsius (275 degree Fahrenheit). Text in Illustration: (asterisk) 1. Engine coolant temperature sensor (asterisk) 2 ECM; (asterisk) 2. Front view of wire harness connector (to engine coolant temperature sensor). Text in Illustration: (asterisk) 1. Engine coolant temperature sensor (asterisk) 2 ECM; (asterisk) 2. Front view of wire harness connector (to engine coolant temperature sensor). Hint: Perform “Inspection after repair” after replacing the engine coolant temperature sensor; NG: Go to step 3. Ok: Replace engine coolant temperature sensor. 3. Check harness and connector (engine coolant temperature sensor - ECM). a) Disconnect the engine coolant temperature sensor connector. (b) Disconnect the ECM connector. (c) Measure the resistance according to the value(s) in the TABLE below. Standard resistance: Tester connection: E47-2 (THW) - E26-95 (THW); Condition: Always; Specified Condition Below 1 ¬ohm; E47-1 (E2) - E26-96 (ETHW); Condition: Always; Specified Condition Below 1 ¬ohm. NG; Repair or replace harness or connector; OK: Replace ECM. Back to Figure The text reads: Monitor Result: Refer to detailed information in checking monitor status. P0300: Misfire / EWMA misfire; The headers are Monitor Id; Test Id; Scaling; Unit; Description: Row 1: Dollar A1; Dollar 0B; Multiply by 1; Time; Total EWMA misfire count of cylinder 1 in last ten driving cycles; Row 2: Dollar A1; Dollar 0C; Multiply by 1; Time; • When ignition switch is ON, total misfire count of all cylinders in last driving cycle is displayed. • While engine is running, total misfire count of all cylinders in current driving cycle is displayed. P0300: Misfire / EWMA misfire: Row 3: Dollar A1; Dollar 0B; Multiply by 1; Time; Total EWMA misfire count of all cylinders in last ten driving cycles. P0301: Misfire / EWMA misfire1: Row 4 Dollar A2; Dollar 0B; Multiply by 1; Time; Total EWMA (asterisk) misfire count of cylinder 1 in last ten driving cycles. P0301: Misfire / misfire rate1: Row 4: Dollar A2; Dollar 0C; Multiply by 1; Time; • When ignition switch is ON, total misfire count of cylinder 1 in last driving cycle

is displayed. • While engine is running, total misfire count of cylinder 1 in current driving cycle is displayed. Back to Figure The headers are: DTC No; DTC Detection Condition; Trouble Area: Row 1: P0300: Simultaneous misfiring of several cylinders occurs and one of the following conditions is met (2 trip detection logic).• A misfire occurs that may damage the three-way catalytic converter (MIL blinks when detect immediately).• An emission deterioration misfire occurs (MIL illuminates): • Open or short in engine wire harness• Connector connection• Vacuum hose connections• Ignition system• Fuel injector assembly• Fuel pressure• Mass air flow meter sub-assembly• Engine coolant temperature sensor. Row 2: P0301, P0302, P0303, and P0304: Misfiring of a specific cylinder occurs and one of the following conditions is met (2 trip detection logic). • A misfire occurs that may damage the three-way catalytic converter (MIL blinks when detect immediately). • An emission deterioration misfire occurs (MIL illuminates). • Compression pressure• Valve timing• PCV valve and hose• PCV hose connections• Intake system• Intake air control valve actuator (for tumble control valve) • ECM. Back to Figure The x axis of the graph is labeled vehicle speed and is scaled as ignition switch on, idling, 60 kilometer per hour, and 135 kilometer per hour. Ignition switch on is marked A, idling at warming up is marked B, idling for 2 minutes or more is marked C, speed of approximately 130 kilometer per hour for 5 minutes or more is marked D, and idling after that speed is marked E. Back to Figure The text reads: DTC P0171 System too lean (bank 1); DTC P0172 System too rich (bank 1). Description: The fuel trim is related to the feedback compensation value, not to the basic injection duration. The fuel trim consists of both the shortterm and long-term fuel trims. The short-term fuel trim is fuel compensation that is used to constantly maintain the air fuel ratio at stoichiometric levels. The signal from the air fuel ratio sensor indicates whether the air fuel ratio is rich or

lean compared to the stoichiometric ratio. This triggers a reduction in the fuel injection volume if the air fuel ratio is rich and an increase in the fuel injection volume if lean. Factors such as individual engine differences, wear over time and changes in operating environment cause short-term fuel trim to vary from the central value. The long-term fuel trim, which controls overall fuel compensation, compensates for long-term deviations in the fuel trim from the central value caused by the short-term fuel trim compensation. The headers are: DTC No; Detection Condition; Trouble Area: Row 1: P0171: With a warm engine and sTABLE air fuel ratio feedback, the fuel trim is considerably in error to the lean side (2 trip detection logic). • Intake system• Fuel injector assembly blockage• Mass air flow meter subassembly• Engine coolant temperature sensor• Fuel pressure• Gas leak from exhaust system• Open or short in air fuel ratio sensor (sensor 1) circuit• Air fuel ratio sensor (sensor 1) • PCV valve and hose• PCV hose connections• Wire harness or connector• ECM. Row 2: P0172: With a warm engine and sTABLE air fuel ratio feedback, the fuel trim is considerably in error to the rich side (2 trip detection logic). • Intake system• Fuel injector assembly leak or blockage• Mass air flow meter sub-assembly• Engine coolant temperature sensor• Ignition system• Fuel pressure• Gas leak from exhaust system• Open or short in air fuel ratio sensor (sensor 1) circuit• Air fuel ratio sensor (sensor 1) • Wire harness or connector• ECM. Back to Figure Typical Malfunction Thresholds Fuel Trim: Row 1: Purge-cut: Executing; Row 2: Either of the following conditions is met1 or 2; Row 3: 1. Average between short-term fuel trim and long-term fuel trim: 35 percent or higher (varies with engine coolant temperature); Row 4: 2. Average between short-term fuel trim and long-term fuel trim: 35 percent or less (varies with engine coolant temperature). Back to Figure The text reads: Typical Enabling Conditions; Monitor runs whenever the following DTCs are not stored: P0010 (VVT oil control valve) P0011 (VVT system - advance) P0012 (VVT system - retard)P0013 (Exhaust VVT oil control valve) P0014 (Exhaust VVT system - advance) P0015 (Exhaust VVT system retard) P0016 (VVT system - misalignment) P0017 (Exhaust VVT system -

misalignment) P0031, P0032, P0101D (Air fuel ratio sensor heater) P0102, P0103 (Mass air flow meter) P0115, P0117, P0118 (Engine coolant temperature sensor)P0120, P0121, P0122, P0123, P0220, P0222, P0223, P2135 (Throttle position sensor) P0125 (Insufficient coolant temperature for closed loop fuel control)P0335 (Crankshaft position sensor) P0340, P0342, P0343 (Camshaft position sensor) P0351 - P0354 (Igniter) P0365, P0367, P0368 (Exhaust camshaft position sensor)P0500 (Vehicle speed sensor) P219A, P219C, P219D, P219E, P219F (Air fuel ratio imbalance). Fuel system status: Closed loop; Battery voltage: 11 Volt or higher; Either of the following conditions is met: 1 or 2; 1. Engine speed: Less than 800 rpm; 2. Engine load: 11.875 percent or higher; Catalyst monitor: Not executed. Back to Figure The text reads: DTC P0171 System too lean (bank 1); DTC P0172 System too rich (bank 1). Description: The fuel trim is related to the feedback compensation value, not to the basic injection duration. The fuel trim consists of both the shortterm and long-term fuel trims. The short-term fuel trim is fuel compensation that is used to constantly maintain the air fuel ratio at stoichiometric levels. The signal from the air fuel ratio sensor indicates whether the air fuel ratio is rich or lean compared to the stoichiometric ratio. This triggers a reduction in the fuel injection volume if the air fuel ratio is rich and an increase in the fuel injection volume if lean. Factors such as individual engine differences, wear over time and changes in operating environment cause short-term fuel trim to vary from the central value. The long-term fuel trim, which controls overall fuel compensation, compensates for long-term deviations in the fuel trim from the central value caused by the short-term fuel trim compensation. The headers are: DTC No; Detection Condition; Trouble Area: Row 1: P0171: With a warm engine and sTABLE air fuel ratio feedback, the fuel trim is considerably in error to the lean side (2 trip detection logic). • Intake system• Fuel injector assembly blockage• Mass air flow meter subassembly• Engine coolant temperature sensor• Fuel pressure• Gas leak from exhaust system• Open or short in air fuel ratio sensor (sensor 1) circuit• Air fuel ratio sensor (sensor 1) • PCV valve and hose• PCV hose connections• Wire harness or connector• ECM. Row 2: P0172: With a warm engine and sTABLE air fuel ratio feedback, the fuel trim is considerably in error to the rich side (2 trip detection logic). • Intake system• Fuel injector assembly leak or blockage• Mass air flow meter sub-assembly• Engine coolant temperature sensor• Ignition system• Fuel

pressure• Gas leak from exhaust system• Open or short in air fuel ratio sensor (sensor 1) circuit• Air fuel ratio sensor (sensor 1) • Wire harness or connector• ECM. Back to Figure The text reads: NG Go to step 16 OK Check for exhaust gas leak. (a) Check the fuel pressure. INFO: NG Repair or replace fuel system. Check for exhaust gas leak. (a) Check for exhaust gas leaks. OK: No gas leaks. Hint: Perform “inspection after repair” after repairing or replacing the exhaust system. INFO. NG Repair or replace exhaust system. Back to Figure The parts labeled are: Protection tube: Protect the element from gas velocity or foreign material in exhaust gas; Zirconia Element Generate voltage output in response to O2 concentration; Ceramic Heater Heating up of the element; Filter Breathable, water proof filter. Reference air can go through the filter; Lead Wire Transfer the signal from sensor to engine control unit. Back to Figure A line graph is titled sensor voltage. The x-axis scaled from 0.9 to 1.1 and labeled air fuel mixture and y-axis is listed with rich 0.9 and lean 0.1 and labeled Volt (Volt). Initially the line starts from (0.9, 0.9) and drops to (1.1, 0.1). A voltage meter shows the reading on the device. The text below the illustration reads: on the contrary, lean mixture drops the voltage down to 0.1 v. Back to Figure The text reads: Typical Enabling Conditions: All: Monitor runs whenever following DTCs not stored: None. Header 1: P0037 (Case 1): Battery voltage: 10.5 Volt or more; Engine: Running; Starter: OFF; Catalyst active air fuel ratio control: Not operating; Time after heater on: 10 seconds or more; Oxygen sensor heater high current (P0038): OK; Learned heater off current operation: Complete; Heater off current learned value: Acquired; Header 2: P0037 (Case 2): Battery voltage: 10.5 Volt or more; Engine: Running; Starter: OFF; Catalyst active air fuel ratio control: Not operating; Time after heater on: 10 seconds or more; Oxygen sensor heater high current (P0038): OK; Learned heater off current operation: Complete; Heated oxygen sensor heater off current: More

than 3.5 A; Hybrid DC high current limiter monitor input: Fail. Back to Figure The text on the top reads: Parameter AF lambda (B1S1) Value 1.0043; AFS voltage (B1S1) Value 3.30 Unit v; AFS current (B1S1) Value 0.00 Unit Volt; milliampere. Next to it is a box labeled Stoichiometric. Below it is A/F sensor. Next to it is two AF on the right and left. The left AF is labeled ECU. Below it is 2.9 Volt constant voltage circuit. The right AF is labeled current flow direction. Below is 3.3 Volt constant voltage circuit. Below the box is 2.9 Volt Electromotive force: approx. 0.4 Volt No current flows in either direction. Back to Figure Three rectangular boxes are shown in the photo. Parts labeled on the top box are: Reference cell, ceramic substrate, alumina and Porous YSZ (Electrolyte and diffusion barrier). The box on the bottom is labeled current is greater than 0; fuel lean condition and the box on the bottom right is labeled current0; fuel rich condition. Back to Figure In the graph x-axis is labeled A/F ratio and Lambda and y-axis is labeled AFS (Volt) and AFS (milliampere). The approximate values are listed as follows: (12, minus 0.54); (12.5, minus 0.44); (13, minus 0.28); (13.5, minus 0.20); (14, minus 0.10); (14.5, 0.04); (15, 0.10); (15.5, 0.16); (16, 0.22); (16.5, 0.24); (17, 0.33); (17.5, 0.35); (18, 0.39); and (18.5, 0.42). Back to Figure The illustration is titled: Reference (System Diagram of Sensor 1). The parts labeled on the three boxes from left to right are as follows: From battery, EFI main no 2, From EFI main relay, EFI main 2, B, heater, A1A, sensor, air fuel ratio sensor, HA1A, A1A, HA1A, A1A, A1A, duty control, and ECM. Back to Figure The text reads: Bank• Specific group of cylinder sharing a common control sensor, bank 1 always contains cylinder number 1; bank 2 is the opposite bank. No. of sensor• Location of a sensor in relation to the engine air flow, starting from the fresh air intake through to the vehicle tailpipe in order numbering 1, 2,

3, and so on. The parts labeled are as follows: vehicle front, HO2S2 (Bank 2), Three ways catalyst (manifold), A/F sensor 1 (Bank 2), A/F sensor 1 (Bank 1), Three ways catalyst (manifold), HO2S2 (Bank 1), Three ways catalyst (under floor), and muffler. Back to Figure The parts labeled are: Air injection control driver, Diagnostic signal, ECM, Command signal, Air switching valve drive signal, Air pump HTR relay, Pressure signal, Air pump drive signal, Air pump assembly, Reed valve, Air switching valve assembly, and Air pressure sensor. Back to Figure The parts labeled are: wire harness, electric air pump, solid state relay, wire harness, air control valve, air control valve, exhaust air supply from electric air pump. Back to Figure The x-axis is unlabeled and unscaled while the y-axis is labeled Air Fuel Ratio Sensor Output and is unscaled. The graph comprises three differently-shaped waves that depict active air fuel ratio control, air fuel ratio sensor output, and fuel injection volume, respectively. The top wave is a square wave with a single crest spanning 10 seconds. Its crest is labeled on and trough is labeled off. The other two waves lie in the same span. The middle wave has two waves superimposed on one another. The first is a typical sine wave drawn with dotted lines and has three cycles of equal wavelengths and amplitude. It is labeled normal. The second is drawn with a solid line and has three cycles of varying wavelengths and amplitude. It is labeled malfunction. The bottom wave is a square wave of three cycles of equal wavelengths and amplitude. Its crest is labeled increase and trough is labeled decrease. Back to Figure The parts labeled are: No. 1 Integration relay, A/pump no 1, air pump assembly, air injection control driver, emission control valve and ECM. Back to Figure The results consist of four sections. General systems, onboard module system,

continuously monitored systems, and monitored test results (mode 6). The text for general systems reads, Command Secondary Air Status: Not reported. Power Takeoff Status: Not reported. Battery Voltage: 14.03. The text for onboard module system reads, Catalyst Monitoring: Completed. Heated Catalyst Monitoring: Not supported. Evaporative System Monitoring: Complete. Secondary Air System Monitoring: Not supported. A/C System Refrigerant Monitoring: Not supported. Oxygen Sensor Monitoring: Complete. Oxygen Sensor Heater Monitoring: Complete. EGR System Monitoring: Complete. The text for continuously monitored system reads, Onboard Module/System: Status. Misfire Monitoring: Complete. Fuel System Monitoring: Complete. Comprehensive Component Monitoring: Complete. The TABLE for Monitored Test Results (Mode 6) shows six columns. Text ID, Component ID, Value, Minimum value, maximum value, and unit. Back to Figure In the graph x-axis is scaled from 10 to 22 with a gap of 2 units and labeled Richer on the left, Air fuel ration at the center and learner on the right and left yaxis 1st bar is scaled from 0 to 3000 with a gap of Nox (ppm) and second bar is scaled from 0 to 150 with random gaps and right y-axis is scaled from 0 to 5 and labeled CO (percent). Best torque A/F range, Best power, Closed-loop mode Target A/F range and Best economy as perpendicular lines and NOx, HC, and CO show random rise and fall. Back to Figure The parts labeled under New ESM DPFE EGR System are map, DPFE signal, sig rtn, VREp, PCM, EGR DC and the parts under sEGR system module (ESM) components are EVR, DPF sensor, map signal EGR valve, fresh air inlet, intake map, delta P equals to P1- MAP, exhaust. Back to Figure The parts labeled are as follows: Throttle body, ignition switch, main relay, ECM, Sensed information: ECT sensor, map sensor, MP sensor, Tp sensor, VSS, EGRT sensor; SV valve, EGR modulator, EGR, valve, EGRT sensor(CA spec vehicle only), intake manifold, exhaust gas, vacuum, and air. Back to Figure

The results consists of four sections. General systems, onboard module system, continuously monitored systems, and monitored test results (mode 6). The text for general systems reads, Command Secondary Air Status: Not reported. Power Takeoff Status: Not reported. Battery Voltage: 14.03. The text for onboard module system reads, Catalyst Monitoring: Completed. Heated Catalyst Monitoring: Not supported. Evaporative System Monitoring: Complete. Secondary Air System Monitoring: Not supported. A/C System Refrigerant Monitoring: Not supported. Oxygen Sensor Monitoring: Complete. Oxygen Sensor Heater Monitoring: Complete. EGR System Monitoring: Complete. The text for continuously monitored system reads, Onboard Module/System: Status. Misfire Monitoring: Complete. Fuel System Monitoring: Complete. Comprehensive Component Monitoring: Complete. The TABLE for Monitored Test Results (Mode 6) shows six columns. Text ID, Component ID, Value, Minimum value, maximum value, and unit. Back to Figure The headers are: DTC: Description: Possible Causes: Diagnostic Aides: Row: P0401 - EGR Flow Insufficient detected: The EGR system is monitored during steady state driving conditions while the EGR is commanded on. The test fails when the signal from the DPF EGR sensor indicates that EGR flow is less than the desired minimum: •Vacuum supply• EGR valve stuck closed• EGR valve leaks vacuum• EGR flow path restricted• EGRVR circuit shorted to PWR• VREF open to DPF EGR sensor• DPF EGR sensor downstream hose off or plugged• EGRVR circuit open to PCM• VPWR open to EGRVR solenoid• DPF EGR sensor hoses both off• DPF EGR sensor hoses reversed• Damaged EGR orifice tube• Damaged EGRVR solenoid• Damaged PCM: Perform KOER self-test and look for DTC P1408 as an indication of a hard fault. If P1408 is not present, look for contamination, restrictions, leaks, and intermittent. Back to Figure The text reads: Bank• Specific group of cylinder sharing a common control sensor, bank 1 always contains cylinder number 1; bank 2 is the opposite bank. No. of sensor• Location of a sensor in relation to the engine air flow, starting from the fresh air intake through to the vehicle tailpipe in order numbering 1, 2, 3, and so on. The parts labeled are as follows: vehicle front, HO2S2 (Bank 2), Three ways catalyst (manifold), A/F sensor 1 (Bank 2), A/F sensor 1 (Bank 1),

Three ways catalyst (manifold), HO2S2 (Bank 1), Three ways catalyst (under floor), and muffler. Back to Figure Text below the illustration reads: Due to partial combustion, the gases entering inside the catalytic converter consists of a mixture of carbon monoxide (CO), unburned hydrocarbons (HC), and oxides of nitrogen (Nox), which are harmful to the environment. Back to Figure The graph is titled: Voltage output when active air fuel ratio control not performed. The x-axis is labeled 10 seconds for normal catalyst and deteriorated catalyst and y-axis is labeled waveform of heated oxygen sensor behind TWC and wave form of air fuel ratio sensor in front of TWC. The first wave under normal catalyst has two regular curves and the second is a straight line. The first wave under deteriorated catalyst has regular curves and the second wave has steep curves. Back to Figure The graph is titled: Voltage output when active air fuel ratio control not performed. The x-axis is labeled 10 seconds for normal catalyst and deteriorated catalyst and y-axis is labeled waveform of heated oxygen sensor behind TWC and wave form of air fuel ratio sensor in front of TWC. The first wave under normal catalyst has two regular curves and the second is a straight line. The first wave under deteriorated catalyst has regular curves and the second wave has steep curves. Back to Figure There are six columns: Description, result, minimum, maximum, test value and unit. The data are as follows: Minimum and maximum oxygen sensor heater, pass, 0.465, 3.000, 0.992, Amps. Back to Figure There are six columns: Description, result, minimum, maximum, test value, and unit. The data are as follows: EGR flow insufficient, pass, 0.99, 655.35, 11.75, kPa.

Back to Figure There are six columns: Description, OBDMID, Test ID, minimum, maximum, and test value. The data are as follows: Catalyst Oxygen Storage Capacity, 21, 81, 0 0.765, 0.085. Back to Figure The parts labeled are as follows: vapor canister, atmosphere, vent solenoid, vent and purge control outputs, purge solenoid, engine vacuum, PCM, fuel level, and tank pressure inputs. Back to Figure The parts labeled are as follows: vehicle control switched, fuel pump relay, battery positive terminal, engine starter motor, power restoration center, ignition switch, power restoration center, evap/purge solenoid, powertrain control module: evap/purge solenoid control, low fuel signal, sensor ground; instrument cluster, fuel pump module: fuel pump relay, sensor ground, fuel level sensor signal, low fuel signal, and ground. Back to Figure The parts labeled are: fuel tank unit: fuel level sensor, fuel pressure sensor; instrument cluster, powertrain control module (PCM): fuel level input, 5v feed, fuel tank pressure, fuel ground and fuel gauge output control, PCM: C1 equals to Red and C2 equals to Blu. Back to Figure The parts labeled are: ECM, EVAP valve, to intake manifold, fuel tank, restrictor passage, refueling valve, charcoal canister, pump module, canister vent valve, 0.020” orifice, pressure sensor, vacuum pump and pump motor, air filter, fresh air line, and purge airline. Back to Figure The parts labeled are: pressure to system, engine vacuum, control switch, control solenoid, pump diaphragm, air from filter, and vent valve. Back to Figure

The x-axis and y-axis are not scaled. The four lines are Purge VSV, Vent valve, Leak detection pump and EVAP pressure. For purge VSV: ON: open, OFF: closed and vent valve: ON: closed, OFF vent while leak detection pump is steadily on for a long duration. The upper and lower motion of EVAP pressure is labeled positive and negative. The labeling are: P0455, P0456, ok, (second reference pressure) (asterisk) 0.2 and (second reference pressure). The sequence is listed at the bottom: a 60 seconds, b 360, c within 15 minutes, d 10, and e 60. Back to Figure The texts read: 2. Purge flow monitor• The 1st monitor: The purge flow monitor consists of 2 monitors. The 1st monitor is conducted every time and the 2nd monitor is activated if necessary. While the engine is running and the purge VSV is on (open), the ECM monitors the purge flow by measuring the EVAP pressure charge. If negative pressure is not created, the ECM begins the 2nd monitor. • The 2nd monitor: The vert valve is turned on (closed) and the EVAP pressure is then measured. If the variation in the pressure is less than 0.15 Kilopascal (gauge) [1.125 millimeter Mercury (gauge)], the ECM interprets this as the purge VSV being stuck closed. Illuminates the MIL and stores DTC P0441 (2 trip detection logic). Back to Figure The x-axis and y-axis are not scaled. The four lines are Purge VSV, Vent valve, Leak detection pump and EVAP pressure. For purge VSV: ON: open, OFF: closed and vent valve: ON: closed, OFF vent while leak detection pump is steadily on for a long duration. The upper and lower motion of EVAP pressure is labeled positive and negative. The labeling are: P0455, P0456, ok, (second reference pressure) (asterisk) 0.2 and (second reference pressure). The sequence is listed at the bottom: a 60 seconds, b 360, c within 15 minutes, d 10, and e 60. Back to Figure The parts labeled are: battery, FL- Main, EFI-Main no 1, EFI-Main no 1, EFI no 1, C94 purge VSV, C96, ECM, PRG, A21, and MREL. Back to Figure

The text reads: Non-Continuous Monitoring Tests: Row 1: Catalyst: Supported, Complete; Row 2: Heated catalyst: Unsupported; Row 3: Evaporative system: Supported Row 4: Secondary air system: Unsupported; Row 4 A/C system: Unsupported; Row 5: Oxygen sensor: Supported Complete; Row 7: Oxygen sensor heater: Supported, Complete; Row 8: EGR system Supported, Complete. Back to Figure The text reads: Monitor Strategy: Required sensors/components (Main): Purge VSV Canister pump module; Required sensors/components (Related). Frequency of operation: Once per driving cycle; Duration: Within 20 minutes (varies with amount of fuel in tank); MIL operation: Sequence of operation: 2 driving cycles Purge VSV Canister pump module: None. Back to Figure The text reads: Typical Enabling Conditions: Monitor runs whenever the following DTCs are not stored: None; Atmospheric pressure: 70 Kilopascal (abs) [525 millimeter Mercury (abs)] or higher, and less than 110 Kilopascal (abs) [825 millimeter Mercury (abs)] ; Battery voltage: 10.5 Volt or higher 5; Vehicle speed: Less than 4 kilometer per hour (2.5 meter per hour) Off; Ignition switch: off; Time after key-off: 5, 7, or 9.5 hours; Canister pressure sensor malfunction (P0452, P0453): Not detected; Purge VSV: Not operated by scan tool; Vent valve: Not operated by scan tool; Leak detection pump: Not operated by scan tool; Both of following conditions met before key-off: Conditions 1 and 2; 1. Duration that vehicle is driven: 5 minutes or more; 2. EVAP purge operation: Performed; Engine coolant temperature: 4.4 degree Celsius (40 degree Fahrenheit ) or higher, and less than 35 degree Celsius (95 degree Fahrenheit ); Intake air temperature: 4.4 degree Celsius (40 degree Fahrenheit ) or higher, and less than 35 degree Celsius (95 degree Fahrenheit ). Back to Figure The headers are: Entry Condition: Minimum: Maximum: Row 1: Engine off (soak) time; 6 hrs.; no data; Row 2: Time since engine start-up: 330 sec, 1800 sec; Row 3: Intake air temp 40 degree Fahrenheit, 90 degree to 100 degree Fahrenheit; Row 4: BARO (altitude is less than 8000 ft.) 22.0 inch of mercury; no data; Row 5: Engine load 20 percent: 70 percent; Row 6: Vehicle speed: 40 meter per hour: 80 meter per hour; Row 7: Purge duty cycle: 75 percent: 100

percent; Row 8: Fuel fill level: 15 percent, 85 percent; Row 9: Fuel tank pressure range: minus 17 in.-H2O, 1.5 in.-H2O Monitor. Back to Figure The texts read: Test Result: The headers are: Min: Max: Test Value: Unit: Row 1: Vapor leak hashtag 1: Pass, 7.969, 20.152, millimeter Mercury; Row 2: Vapor leak hashtag 2: Fail, 5.862, 5.496, millimeter Mercury; Row 3: Purge VSV: Pass, 3.114, 0.091, millimeter Mercury; Row 4: EVAP pres. VSV: Pass, 23.358, 0.000, millimeter Mercury. Print, save, close. Back to Figure The headers are: TID: CID: Value: Unit: Min: Max: Result: Time: Row 1: Dollar 00 SUP [Dollar 01 to Dollar 20]: SUP; 21:00:07.9; Row 2: Dollar 09 Therm: Dollar 1, 49103.25, C, 49103.25, Pass, 21:00:10.3; Row 3: Dollar 09 Manuf Def: Dollar 03, minus 1, 65535, Pass, 21:00:10.3; Row 4: Dollar 09 Manuf Def: Dollar 02, minus 1, 65535, Pass, 21:00:10.3; Row 5: Dollar 0A Manuf Def: Dollar 01, 230, 242, Pass, 21:00:12.7; Dollar 0A Row 6: Manuf Def: Dollar 04, 40, 25, Pass, 21:00:12.7; Dollar 0A Manuf Def: Dollar 03, 40, 49, Pass, 21:00:12.7; Row 7: Dollar 0A Manuf Def: Dollar 02, 230, 212, Pass, 21:00:12.7; Back to Figure The parts labeled are road draft tube, fresh air enters through oil filler cap, blowby, and crankcase. Back to Figure In the graph, the x-axis is scaled from 8 to 18 and labeled air fuel ratio and the left and right y-axis is scaled from 0 to 16 and 0 to 2800 and labeled volume (percent of most exhaust) and hydrocarbons and Nox (p.p.m.), respectively. The 8 lines of different colors represent NOx, CO, H2, CO2, water vapor, hydrocarbons and O2. A vertical line x 14.7 is labeled stoichiometric. The effect of changing air/fuel ratio on the levels of NOx, CO, and HC produced in the engine. The diagram also shows qualitatively how the engine power output changes with the A/F ratio. A general relationship between levels of CO, HC, and NOx released from the engine and the A/F ratio is displayed. At A/F ratios somewhat above stoichiometric (14.7:1) – that is, when the engine is operating under fuel-lean, net oxidizing conditions – low levels of HC and CO are

produced in the engine, and there is a peak in NOx concentration. At higher A/F values, NOx falls, but the hydrocarbon concentration increases as the engine begins to misfire. Back to Figure The text reads: Smog check vehicle inspection report (VIR): Test Date/Time: 07/29/20XX. Model Year: 1990; License: Engine Size: 1.6 L; GVWR: N/A; Odometer: 228747; Fuel Type: Gasoline; Make: HONDA; State: CA; Type: Passenger; Test Weight: 2500; Certification: California; Exhaust: Single; Model: CIVIC; VIN; Transmission: Manual; Cylinders: 4; VLT Record #; Inspection Reason: High Emitter Profile. Emission Control Systems Visual Inspection/Functional Check Results (Visual/Functional tests are used to assist in the identification of crankcase and cold start emissions which are not measured during the ASM test). Result: ECS: Pass: PCV; Pass: Catalytic Converter; N/A: EGR Visual; N/A: EGR Functional; Pass: Fuel Cap functional; Pass: Fuel Cap Visual; Pass: Spark Controls; Pass: Fuel Evaporative Controls Functional; N/A: Thermostatic Air Cleaner; N/A: Air Injection; Pass: Vacuum Lines to Sensors/ Switches; Pass: Ignition Timing: 17BTDC; Pass: Wiring to Sensors; N/A: Fillpipe Restrictor; Pass: Fuel Evaporative Controls; Pass: MIL/Check Engine Light; Pass: Carb./Fuel Injection; Pass: Other Emission Related Components; Pass: Oxygen Sensor; Pass: Liquid Fuel Leaks. ASM Emission Test Results; The first headers are: percent CO2; percent O2; HC(PPM); CO (percent); NO (PPM); The second headers are: Test; RPM; MEAS; MEAS; MAX; AVE; MEAS; MAX; AVE; MEAS; MAX; AVE; MEAS; Results; Row 2: 15 meter per hour; 2129; 15.1; 4.1; 94; 37; 149; 0.58; 0.12; 0.43; 567; 443; 1363; FAIL; Row 2: 25 meter per hour; 2435; 15.4; 4.0; 76; 26; 63; 0.49; 0.19; 0.11; 704; 369; 266; PASS. Back to Figure The text reads: Emission Control Systems Visual Inspection/Functional Check Results (Visual/Functional tests are used to assist in the identification of crank case and cold start emissions which are not measured during the ASM test). Result: ECS: Pass: PCV; Pass: Catalytic Converter; N/A: EGR Visual; N/A: EGR Functional; Pass: Fuel Cap functional; Pass: Fuel Cap Visual; Pass: Spark Controls; Pass: Fuel Evaporative Controls Functional; N/A: Thermostatic Air Cleaner; N/A: Air Injection; Pass: Vacuum Lines to Sensors/ Switches; N/A Ignition Timing; Pass: Wiring to Sensors; N/A: Fillpipe Restrictor; Pass: Fuel

Evaporative Controls; Pass: MIL/Check Engine Light; Pass: Carb./Fuel Injection; Pass: Other Emission Related Components; Pass: Oxygen Sensor; Pass: Liquid Fuel Leaks. ASM Emission Test Results; The first headers are: percent CO2; percent O2; HC(PPM); CO (percent); NO (PPM); The second headers are: Test; RPM; MEAS; MEAS; MAX; AVE; MEAS; MAX; AVE; MEAS; MAX; AVE; MEAS; Results; Row 1: 15 meter per hour; 2129; 15.1; 4.1; 74; 9; 14; 0.58; 0.03; 0.11; 430; 67; 1034; FAIL; Row 2: 25 meter per hour; 2435; 15.4; 4.0; 39; 6; 13; 0.49; 0.03; 0.12; 713; 62; 353; PASS. MAX equals to Maximum allowance emissions, AVE equals to Average Emissions for passing vehicles and MEAS equals to Amount measured. Back to Figure The text reads: Inspection Procedure Hint: • If DTCs P0XXX, P0XXX, and P0402 are output simultaneously, perform troubleshooting of DTC PXXXX first. • If DTCs P0XXX and P0XXX are output simultaneously, perform troubleshooting of DTC P0XXX first. Hand-held tester: 1. Check connection of vacuum hose and EGR hose. (asterisk) See page EC-ST).NG Repair or replace. Ok. 2. Check VSV for EGR. Preparation: A) Connect the hand-held tester to the DLG3. B) Turn the ignition switch ON and push the hand-held tester main switch ON. C) Select the ACTIVE TEST mode on the hand-held tester. Check: Check the operation of the VSV when it is specified by the handheld tester. OK: EGR system is OFF: Air from port E comes out through the air filter. EGR system is ON: Air from port E comes out through port G. OK Go to step 6. NG. Two illustration of air filter is shown for OFF and ON condition Back to Figure An illustration shows vacuum hose released from the ports P, R, and Q. P and R ports are blocked with a finger, and the air is blown into port Q. An illustration shows vacuum hose is released from the ports P, R, and Q. P and R ports are blocked with a finger, and the air is blown into port Q while the engine is at 2,500 R P M. An illustration shows the E G R valve. An illustration shows the E G R valve with a gasket. Back to Figure The texts read: Sample Commonwealth of state vehicle emissions inspection report. Test date/time: 03-26-20XX @ 10:50. VEHICLE INFORMATION: Year:

1996; VIN: A1234567890B12345; Odometer: 100000; License: XXX1234; County: PIERCE ROBERT; Make: XXXX; Engine size: 6.0 L; GVWR: 4400; Inspection type: INITIAL; Model: XXXXXXXXXXXX; Cylinders: XXXX; Estimated test: B; Weight: 4400; Record Number: 123456. Emissions control systems visual/functional inspection: Air Pump System: Pass; EGR System: Pass; PCV System: Pass; Fuel Inlet Restrictor: Pass; Catalytic Converter: Pass; Evaporative Control System: Pass; Gas Cap Integrity: Pass; Evaporative Pressure: N/A; Evaporative Purge: N/A. TAILPIPE EMISSIONS INSPECTION. The headers are: MODE; CO; HC ppm; RPM; DILUTION; Row 1: Speed Idle; Limit; Reading; Result; Limit; Reading; Result; Reading; Result; Reading; Result; Row 2: IDLE;1.20; 2.23; FAIL; 220; 360; FAIL; 500; VALID; 13.5 percent; VALID; Row 3: 2500 RPM; 1.20; 2.35; FAIL; 220; 120; PASS; 2400; VALID; 14.3 percent; VALID. OVERALL TEST RESULTS: FAILED: Emissions Control Systems Visual/Functional Inspection: PASS; Tailpipe Emissions Inspection: FAIL; Transaction Identification Number: 123456789. Retain this document for use on reinspection. Return the vehicle to the same station within thirty (30) days for one (1) free retest. This vehicle has failed the emissions inspection. Repairs should be made to either pass reinspection or qualify for a waiver. All emissions related repairs performed must be documented by the inspection station. This inspection report and copies of the repair receipts must be made available to the inspection station at the time of reinspection. Vehicles that fail the inspection may be eligible for warranty coverage for the required repairs. Vehicle manufacturers are required by Federal law to provide EMISSIONS WARRANTIES FOR AT LEAST FIVE (5) YEARS OR FIFTY THOUSAND (50,000) MILES. Warranty coverage may vary depending on vehicle make and model year. For further information, refer to the EMISSIONS WARRANTY section of the vehicle’s owner manual. In order for a vehicle to receive a “WAIVER” when tail pipe levels of CO, HC, and NO (if applicable) and still failing to meet the standards at the time of inspection, the following requirements must be met. 1. REPAIR WORK MUST BE APPROVED BY A CERTIFIED REPAIR TECHNICIAN.2. Emission related repair expenditures must have been at least $ (Dollar)XXX.XX3. Copies of the repair receipts for emissions related repairs must be provided to the inspection station.4. Repairs were performed no earlier than 60 days prior to the initial inspection. Vehicle tested in accordance with 40CFR, Part 51 and Pa. Title 67, Chapter 127. EMISSIONS INSPECTION STATION: STATION #: 12345 STATION NAME: I/M Quality Inspection; ADDRESS: 13901 CIRCLE DRIVE, ANYTOWN 12345012345-6789JOHN A; PHONE: 012-345-6789; INSPECTOR NAME: John A. Samson; INSPECTOR ID: 12345; ANALYZER #: Z123451; SOFTWARE

VERSION: 1.00. VEHICLE EMISSIONS INSPECTION QUESTIONS: If the station cannot answer your questions, please contact the Department of Transportation, Vehicle Inspection Division at (012) 999-9999. Inspector’s Signature: John A. Samson Back to Figure The text reads: Safety and Emissions Inspection: VEHICLES FAILING EMISSIONS TESTS MAY BE ELIGIBLE FOR UP TO $ (Dollar) 600 IN REPAIR ASSISTANCE. FOR MORE INFORMATION, VISIT www.anywebsite.org OR CALL 1-800-000-0000. Vehicle Identification; Station Identification. Test Date/Time: 03/31/20XX, 13:30; Station Name: ARBOR CAR WASH & LUBE CEN; Test and Type: Initial – OBDII; Station #/Analyzer: 6P34907/ES520110; Insp. Type/Exp. Date: N/A; Station Address: 10401 JOLLYVILLE; Version/Test Number: 1601/23324; Station City: ANYTOWN; License Number: SHUFL; Station Zip Code: 00000-0000; Vehicle ID Number: 1FTFWXET7FDFXXXXX; Inspector First Name: DENNIS; Vehicle Make: FORD; Inspector Last Name: SPENCER; Vehicle Model: F150 4WD; Vehicle Year/Type: 2013/Truck/Van; Safety Inspection Fee: No data; Engine Size/Cyl/Ign: 5400/8/c; Safety Repair Costs: No data; Authorization Number: N/A; Emissions Test Fee: No data; Transmission/GVW: Automatic/7650; Emissions Repair Costs; Total Inspection Cost: No data. Odometer/Fuel Type: 104428/Gasoline. Total Inspection Cost: Emissions Test Results. The headers are: Status of Bulb Check: Monitors: Status: Row 1: MIL Cmnd Status: Off; Misfire: Ready; Heated Cat: N/S; O2 Sensor: Not Ready; Row 2: MIL: Fuel Sys: Ready; Evap Sys: Ready; Heated O2: Not Ready; Row 3: Engine On: PASS; Comp Cmpnt: Ready; Secondary: N/S; EGR/VVT: Ready; Row 4: Engine Off: PASS; Catalyst: Not Ready; Air Cond: N/S; DLC: Pass; Fault Codes: No Codes Present; Gas Cap Integrity: PASS; Safety Items: PASS. Fault Codes: No Codes Present. Gas Cap Integrity: PASS. Safety Items: PASS. Overall Result: FAIL. Back to Figure The text reads: Emission Control Systems Visual Inspection/Functional Check Results (Visual/Functional tests are used to assist in the identification of crankcase and cold start emissions which are not measured during the ASM test). Result; ECS; Result; ECS; Result; ECS; Pass; PCV; N/A; Thermostatic Air Cleaner; Pass; Fuel Evaporative Controls; Pass; Catalytic Converter; Pass; Pump Air Injection; Pass; Fuel Tank Cap Visual; N/A; Visual EGR; N/A; Ignition

Spark Controls; N/A; Carburetor; Pass; Fuel Injection; Pass; O2 Sensors and Connectors; Pass; Wiring of Other; Pass; Vacuum Line Connections; Pass; Other Emission Related; Sensors or Switches; N/A; Functional EGR; N/A; Ignition Timing: TDC; FAIL; MIL; N/A; Fillpipe Restrictor; Pass; Liquid Fuel Leaks; N/A; Fuel Evap Test; THIS VEHICLE FAILED MIL/CHECK ENGINE LIGHT DUE TO A WARNING LAMP FAILURE; Fault Codes: P0313: Misfire detected with low fuel;P0083: P0135: O2 Sensor Heater Fault (Bank 1, Sensor 1); P0153: O2 Sensor Heater Fault (Bank 2, Sensor 1); P0171: System Too Lean (Bank 1); P0174: System Too Lean (Bank 2); ASM Emission Test Results; The first headers are: percent ; CO2; percent ; O2; HC (PPM); CO ( percent ); NO (PPM); The second heading are: Test; RPM; MEAS; MEAS; MAX; AVE; MEAS; MAX; AVE; MEAS; MAX; AVE; MEAS; Results; Row 1: 15 meter per hour; 1790; 14.57; 0.07; 51; 4; 5; 0.48; 0.01; 0.64; 419; 27; 871; FAIL; Row 2: 25 meter per hour; 1346; 14.30; 0.00; 35; 4; 12; 0.86; 0.01; 0.72; 706; 26; 128; FAIL; MAX equals to Maximum Allowable Emissions; AVE equals to Average Emissions for Passing Vehicles; MEAS equals to Amount Measured. Back to Figure The text reads: Smog check vehicle inspection report (VIR): Test Date/Time: 02/24/20XX. Model Year: 1985; License: Engine Size: 5.3L; GVWR: 6100; Odometer: 647; Fuel Type: Gasoline; Make: CHEVROLET; State: Unknown; Type: Truck; Test Weight: 4060; Certification: California; Exhaust: Dual; Engine year 2012; Model: C10PICKUP; VIN; Transmission: Automatic; Cylinders: 8; VLT Record # 01049; Inspection Reason: Initial Registration. Overall Test Results; Comprehensive Visual Inspection: PASS; Functional Check: PASS; Emissions Test: FAIL; Repairing your vehicle is necessary to help California reduce smog forming emissions and reach our air quality goals. Emission Control Systems Visual Inspection/Functional Check Results (Visual/Functional tests are used to assist in the identification of crankcase and cold start emissions which are not measured during the ASM test). Result; ECS; Result; ECS; Result; ECS; Pass; PCV; N/A; Thermostatic Air Cleaner; Pass; Fuel Evaporative Controls; Pass; Catalytic Converter; N/A; Air Injection; Pass; MIL/Check Engine Light; N/A; EGR Visual; Pass; Vacuum Lines to Sensors/; Pass; Carb./Fuel Injection; N/A; EGR Functional; Switches; Modified; Pass; Pass; Fuel Evaporative Controls; MIL/Check Engine Light; Carb./Fuel Injection; Other Emission Related; Pass; Fuel Cap functional; N/A; Ignition Timing: 17 BTDC; Components; Pass; Fuel Cap Visual; Modified; Pass; Thermostatic Air Cleaner; Air Injection; Vacuum Lines to Sensors/; Switches; Ignition Timing: 17

BTDC; Wiring to Sensors; Pass; Oxygen Sensor; Pass; Spark Controls; Pass; Fillpipe Restrictor Pass; Liquid Fuel Leaks; N/A; Fuel Evaporative Controls Functional; ASM Emission Test Results; The first headers are: percent CO2; percent ; O2; HC (PPM); CO ( percent ) NO (PPM); The second headers are: Test; RPM; MEAS; MEAS; MAX; AVE; MEAS; MAX; AVE; MEAS; MAX; AVE; MEAS; Results; Row 1:15 meter per hour; 1511; 14.0; 0.1; 108; 4; 11; 0.43; 0.01; 0.01; 1004; 14; 0; PASS; Row 2: 25 meter per hour; 1476; 13.9; 0.4; 97; 4; 4; 1.07; 0.01; 0.01; 969; 19; 0; PASS; MAX equals to Maximum Allowable Emissions; AVE equals to Average Emissions for Passing Vehicles; MEAS equals to Amount Measured. Back to Figure The text reads: Smog check vehicle inspection report (VIR): Test Date/Time: 07/29/20XX. Model Year: 1997; License: Engine Size: 2.4L; GVWR: N/A; Odometer: 174984; Fuel Type: Gasoline; Make: NISSAN; State: California; Type: Passenger; Test Weight: 3124; Certification: California; Exhaust: Single; Model: 240SK; VIN; Transmission: Automatic; Cylinders: 4; VLT Record #; Inspection Reason: KTP; Bar Number: N/A; Overall Test Results; Comprehensive Visual Inspection: PASS; Functional Check: PASS; Emissions Test: FAIL; Repairing your vehicle is necessary to help California reduce smog forming emissions and reach our air quality goals. Emission Control Systems Visual Inspection/Functional Check Results (Visual/Functional tests are used to assist in the identification of crankcase and cold start emissions which are not measured during the ASM test). Result; ECS; Result; ECS; Result; ECS; Pass; PCV; Pass; Fuel Evaporative Controls; Pass; Catalytic Converter; Pass; EGR Visual; Pass; Spark Controls; Pass; Fuel Injection; Pass; Oxygen Sensor; Pass; Wiring to Sensors; Pass; Vacuum Lines to Sensors/; Pass; Other Emission Related; Pass; Liquid Fuel Leaks; Switches; Components; Pass; Malfunction Indicator Light; Pass; Fuel Cap Integrity Test; Pass; Fuel Cap Visual; Pass: Ignition Timing: 21 BTDC.. ASM Emission Test Results; The first headers are: percent CO2; percent O2; HC(PPM); CO (percent); NO (PPM); The second headers are: Test; RPM; MEAS; MEAS; MAX; AVE; MEAS; MAX; AVE; MEAS; MAX; AVE; MEAS; Results; Row 1: 15 meter per hour; 1496; 14.6; 0.5; 58; 9; 7; 0.52; 0.02; 0.00; 451; 57; 645; FAIL; 25 meter per hour; 1712; 14.6; 0.4; 42; 7; 5; 0.50; 0.03; 0.00; 736; 50; 534; PASS. MAX equals to Maximum allowance emissions, AVE equals to Average Emissions for passing vehicles and MEAS equals to Amount measured.

Back to Figure The text reads: Smog check vehicle inspection report (VIR): Test Date/Time: 07/29/20XX. Model Year: 1990; License: Engine Size: 1.6 L; GVWR: N/A; Odometer: 228747; Fuel Type: Gasoline; Make: HONDA; State: CA; Type: Passenger; Test Weight: 2500; Certification: California; Exhaust: Single; Model: CIVIC; VIN; Transmission: Manual; Cylinders: 4; VLT Record #; Inspection Reason: High Emitter Profile. Overall Test Results; Comprehensive Visual Inspection: PASS; Functional Check: PASS; Emissions Test: FAIL; Repairing your vehicle is necessary to help California reduce smog forming emissions and reach our air quality goals. Emission Control Systems Visual Inspection/Functional Check Results (Visual/Functional tests are used to assist in the identification of crankcase and cold start emissions which are not measured during the ASM test). Result: ECS: Pass: PCV; Pass: Catalytic Converter; N/A: EGR Visual; N/A: EGR Functional; Pass: Fuel Cap functional; Pass: Fuel Cap Visual; Pass: Spark Controls; Pass: Fuel Evaporative Controls Functional; N/A: Thermostatic Air Cleaner; N/A: Air Injection; Pass: Vacuum Lines to Sensors/ Switches; Pass: Ignition Timing: 17BTDC; Pass: Wiring to Sensors; N/A: Fillpipe Restrictor; Pass: Fuel Evaporative Controls; Pass: MIL/Check Engine Light; Pass: Carb./Fuel Injection; Pass: Other Emission Related Components; Pass: Oxygen Sensor; Pass: Liquid Fuel Leaks. ASM Emission Test Results; The first headers are: percent CO2; percent O2; HC(PPM); CO (percent); NO (PPM); The second headers are: Test; RPM; MEAS; MEAS; MAX; AVE; MEAS; MAX; AVE; MEAS; MAX; AVE; MEAS; Results; Row 1: 15 meter per hour; 2129; 15.1; 4.1; 94; 37; 149; 0.58; 0.12; 0.43; 567; 443; 1363; FAIL; Row 2: 25 meter per hour; 2435; 15.4; 4.0; 76; 26; 63; 0.49; 0.19; 0.11; 704; 369; 266; PASS. MAX equals to Maximum allowance emissions, AVE equals to Average Emissions for passing vehicles and MEAS equals to Amount measured. Back to Figure The text reads: Emission Control Systems Visual Inspection/Functional Check Results (Visual/Functional tests are used to assist in the identification of crankcase and cold start emissions which are not measured during the ASM test): Result: ECS: Result: ECS: Result: ECS: Pass: PCV; N/A: Thermostatic Air Cleaner; Pass: Fuel Evaporative Controls: Pass: Catalytic Converter; N/A: Air Injection; Pass: MIL/Check Engine Light; N/A: EGR Visual; Pass: Vacuum Lines to Sensors/; Pass: Carb./Fuel Injection; N/A: EGR Functional; Switches; Pass:

Other Emission Related; Pass: Fuel Cap functional; Pass: Ignition Timing: 17 BTDC; Components; Pass: Fuel Cap Visual; Pass: Wiring to Sensors; Pass: Oxygen Sensor; Pass: Spark Controls; Pass: Fillpipe Restrictor; Pass: Liquid Fuel Leaks; Pass: Fuel Evaporative Controls Functional. ASM Emission Test Results; The first headers are: percent CO2; percent O2; HC(PPM); CO (percent); NO (PPM); The second headers are: Test; RPM; MEAS; MEAS; MAX; AVE; MEAS; MAX; AVE; MEAS; MAX; AVE; MEAS; Results; Row 1: 15 meter per hour: 1873: 14.1:0.1: 59: 21: 18: 0.34: 0.41: 1.31: 406: 114: 102: PASS: Row 2: 25 meter per hour: 2435: 14.1: 0.1: 31: 19: 0: 1.30: 0.04: 1.40: 149: 121: 154: FAIL. MAX equals to Maximum Allowable Emissions: AVE equals to Average Emissions for Passing Vehicles: MEAS equals to Amount Measured. Back to Figure The headers are: Description: Limits: Actual Value: Row 1: Engine oil temperature Min 60 degree Celsius Not checked Temp gauge checked. Fast Idle Test: FAIL; Row 2: Engine Speed: 2500 to 3000 rpm, NOT CHECKED; Row 3: CO: less than equal to 0.20 percent, 4.75 percent : FAIL; Row 4: HC: less than equal to 200 ppm, 773 ppm, Fail; Row 5: Lambda: 0.97 to 1.03, 0.854, Fail; Second Idle Test: FAIL; Row 6: Engine Speed: 2500 to 3000 rpm, NOT CHECKED; Row 7: CO: 0.20 percent, 4.75 percent : FAIL; Row 8: HC: less than equal to 200 ppm, 385 ppm, Fail; Row 9: Lambda: 0.97 to 1.03, 0.939, Fail. Natural Idle Test: FAIL; Row 10: Engine Speed: 450 to 1500 rpm, Not checked; Row 11: CO: less than equal to 0.30 percent, 2.01 percent, Fail; Overall Result: Exhaust Emissions Test, FAILED; Test Start: 17.08.20XX 13:03; Test End: 17.08.20XX 13.26; Tested by: JOHN SMITH. Back to Figure Text reads, “Conforms to regulations: 2018 MY. U.S. EPA: T3B70 LDT4 CA OBD 2. Fuel: Gasoline. California: ULEV70 LDT CA OBD 2. Fuel: Gasoline. TWC/DFI/SFI/WR-HO2S/HO2S/TC/CAC. No adjustments needed. 3.5L-Group: JFMXT03.54JK. Evap: JFMXR0260NDP. JW7E-9C485-CLK.” A bar code is at the bottom of the label. Back to Figure The illustration is titled Freudenburg active engine mount. The parts labeled are: Actuator, diaphragm, outer reservoir, working reservoir, rubber element,

balance reservoir, bellows. The text below it reads: At low frequencies (20 Hz) the mount behaves as a conventional hydromount. • At high frequencies the inertia of the fluid is high decoupling the working and balance reservoirs. • At high frequencies the generated forces are in anti-phase with the dynamic forces generated by the engine Diaphragm Actuator Freudenburg. Back to Figure The parts labeled are: piston, pre-ignition, spark plug, intake valve, fuel injector, air chamber, camshafts, exhaust valve, cylinder. Back to Figure Text reads, Row 1. Accelerator Pedal. Position Sensor 1 (APP 1): 0 percent/0.50 Volt. Accelerator Pedal Position Sensor 1 (APP 1): 0 percent/1.50 Volt. Crankshaft Position Sensor (C K P): 300 rpm. Engine Coolant Temperature Sensor (E C T): −40 degrees Fahrenheit/40 degrees Celsius/5.0 Volt. Row 2. Fuel Enable: YES. Ignition Switch: START. Intake Air Temperature Sensor (I A T): −40 degrees Fahrenheit/40 degrees Celsius/5.0 Volt. Manifold Absolute Press Sensor (M A P): 101 kPa/0 in. Hg/5.0. Row 3. Mass Airflow Sensor (M A F): 175 gm/sec/5.0 Volt. Throttle Actuator Control Motor (T A C): 15 percent. Throttle Position Sensor 1 (T P 1): 0 percent/5.0 Volt. Throttle Position Sensor 2 (T P 2): 0 percent/5.0 Volt. Back to Figure The parts labeled are: coolant temperature sensor; 12 Volts; computer; 5 Volts and voltage sensing circuit. Back to Figure Three are three columns: Engine speed, idle, and 2000 rpm. Row entries are as follows: Row 1. H C (p p m), 500, 15. Row 2. C O (percent), 0.3, 0.1. Row 3. C O2 (percent), 13.0, 14.2. Row 4. O2 (percent), 0.2, 0.5. Back to Figure Text reads, “Conforms to regulations: 2018 MY. U.S. EPA: T3B70 LDT4 CA OBD 2. Fuel: Gasoline. California: ULEV70 LDT CA OBD 2. Fuel: Gasoline. TWC/DFI/SFI/WR-HO2S/HO2S/TC/CAC. No adjustments needed. 3.5L-Group:

JFMXT03.54JK. Evap: JFMXR0260NDP. JW7E-9C485-CLK.” A bar code is at the bottom of the label. Back to Figure Text reads, “Conforms to regulations: 2018 MY FFV. U.S. EPA: T2B5 LDV. OBD F2. Fuel: Gasoline/Ethanol. California: Not for sale in states with California emissions standards. TWC/HO2S/ WR-HO2S/DFI. No adjustments needed. 2.0L-Group: FFMXV02.0VE3. Evap: FFMXR0110GBA. FW7E-9C485-ZUP. A bar code is at the bottom of the label. Back to Figure There are four column headers: temperature measured in degree Celsius, temperature in degree Fahrenheit, Res in Ohms, and Voltage 2.2 K Pullup in Volts. Data from the TABLE are as follows: Row 1: negative 40, negative 40, 402K, 4.97; Row 2: negative 35, negative 31, 289K, 4.96; Row 3: negative 30, negative 22, 210K, 4.95; Row 4: negative 25, negative 13, 154K, 4.93; Row 5: negative 20, negative 4, 114K, 4.91; Row 6: negative 15, 5, 85.0K, 4.87; Row 7: negative 10, 14, 64.3K, 4.83; Row 8: negative 5, 23, 48.9K, 4.78; Row 9: 0, 32, 37.5K, 4.72; Row 10: 5, 41, 29.0K, 4.65; Row 11: 10, 50, 22.5K, 4.56; Row 12: 15, 59, 17.7K, 4.45; Row 12: 20, 68, 14.0K, 4.32; Row 13: 25, 77, 11.1K, 4.18; Row 14: 30, 86, 8.9K, 4.01; Row 15: 35, 95, 7.2K, 3.83; Row 16: 40, 104, 5.8K, 3.63; Row 17: 45, 113, 4.7K, 3.42; Row 18: 50, 122, 3.9K, 3.20; Row 19:55, 131, 3.2K, 2.97; Row 20: 60, 140, 2.7K, 2.74; Row 21: 65, 149, 2.2K, 2.52; Row 22: 70, 158, 1.9K, 2.30; Row 23:75, 167, 1.5K, 2.09; Row 24: 80, 176, 1.3K, 1.88; Row 25: 85, 185, 1.1K, 1.70; Row 26: 90, 194, 965, 1.52; Row 27: 95, 203, 826, 1.37; Row 28: 100, 212, 710, 1.22; Row 29: 105, 221, 613, 1.09; Row 30: 110, 230, 531, 0.97; Row 31: 115, 239, 462, 0.87; Row 32: 120, 248, 403, 0.77; Row 33: 125, 257, 352, 0.69; Row 34:130, 266, 309, 0.62; Row 35: 135, 275, 272, 0.55; Row 36: 140, 284, 241, 0.49; Row 37:145, 293, 213, 0.44; Row 38:150, 302, 189, 0.40. Back to Table