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Library of Congress Cataloging-in-Publication Data

Anello, John Automotive Computer Diagnostics - Real World Training p.

Cm.

TXu 885-880 Copyright Š 1998,1999,2008 by John Anello

- third edition

g reserved. This manual is copyrighted py g under Federal Law to pprevent the All rights unauthorized use or copying of its contents. Under copyright laws no part of this manual can be reproduced, copied or transmitted in any form without the written permission of its author John Anello of Auto Tech On Wheels Inc.

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Editor’s Desk A scant few years after I’d started making my living as a mechanic, I became pretty sure I was the best wrench around, able to solve problems nobody else could and repair cars and trucks so that problem, at least, never occurred again. I was wrong, of course, but I didn’t find that out for a couple more years. Most of us, in our heart of hearts, suspect the same thing for a good part of our working life. After all, we don’t really know that many mechanics’ work if they aren’t ’t att the th same shop h we are.We W do d all ll our own work, k after ft all, ll andd only l see other th people’s mistakes. As I started writing more articles and meeting more mechanics, I came to the realization that there were occasional people, in fact a lot of them, who could give me a real run for the money. A year or two ago I wrote an article in Import Service magazine about John Anello’s unusual automotive business, diagnosing only the most difficult of cars, those other shops had given up on - and all of it on a payment-only-after-success basis. basis I followed him around one day while he went through a dozen cars, figuring out almost all of them. He is, in plain words, the most amazing diagnostician I’ve ever seen, partly from the experience of doing that most of the time and partly from his own 100-mph disposition and good head. There may be somebody somewhere who is faster than he is, or there may be g y higher g battingg average. g But I doubt there’s anybody y y with someone with a slightly that combination of speed and accuracy. So I was very honored when he asked me to read through his instruction book and make suggestions. Except for editorial suggestions, the book is entirely his work; and fascinating work it is, drawn from the daily nightmare puzzles he solves one after another. The cars he sees are not clean, factory fresh jobs or engines on a display stand. These are the same kind you see, complete with rust, previous amateur repairs and other mistakes, multiple problems and general neglect. As he says in the title, this instruction is “real world,” with all the grit and nicks and dents you’d expect to find in a couple hundred cars from New Jersey. While John is an engaging writer and makes his points clearly, this is not an easyreading, coffee-table book. There’s no fat in it and no slackening off the fast pace, so if you drift off, you’ll miss something important. He wrote the book to accompany the th di diagnostic ti course he h has h preparedd andd has h given i now severall times ti on the East Coast, but the book can also be of interest and use to people who can’t take advantage of the course.There is probably more real-world automotive diagnostic information in fewer words and pages here than in anything else you’ll find to read. Joe Woods T h i l Editor, Technical Edit Import I t Service S i Magazine M i

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A k Acknowledgments l d I would like to give a special thanks to the many people, especially my wife, who inspired me to write this book and who gave me a lot of support along the way. I spent the full summer of 1998 putting this book together and invested close to 600 hours of my free time. I tried to make it as “real world� as possible so that you will not onlyy ggraspp the theory y behind how a system y functions but also understand how the different factors of real world occurrences can play havoc in your daily diagnostic routines. All of the photos in this book were taken on job sites and really give you the close encounter feel of what goes on out there in the shop environment. Even the data files I present all came from my own personal files of cars I have previously diagnosed. Along with the many diagrams I drew, the book will give you the sense of being or been there atmosphere. I hope this book can only inspire other techs to realize the potential they have to become a master in the field of diagnostics!

List of Acknowledgments: To Jorge Menchu from AES who always found time for the many questions I presented him with and allowing me to overcome many hurdles in my quest to produce this book. To Tom Petty from Petty Diagnostics and Technical Services who helped to lay my foundation for starting my seminars by providing me with a lot of insight and pointing me in the right direction. To Jim Linder from Linder Technical Services who provided me with a lot of inspiration for my seminars and found the time to always answer the many questions I confronted him with. To Joe Woods from Import Service who really did a great job editing my book and teaching me to be a better writer. John Anello President, Auto Tech On Wheels

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Table Of Contents Introduction……………………………………….………………….9 Welcome to the Real World……………………………………..….10 Bottom Flow…………………………………………………………11 Diagnostic Road……………………………………………………..12 ECM Power and Ground operation………………………...………..13 ECM Ref ground/Ref voltage operation…………………………….14 ECM grounds a) Loose ground……………………………………………15 b) High resistance #1………………………………………16 c) High Resistance #2……………………………………..17 d) Weak/Corroded #1……………………………………….18 e) Weak/Corroded #2………………………………………19 ECM power feeds: a) ECM power failures…………………………………….20 b) Fuse link repair………………………………………….21 c) Power failure culprits……………………………………22 d) Power relay failure………………………………………23 e) Relay water intrusion…………………………………….24 f) Ignition feed failure #1……………………………………25 g) Ignition feed failure #2……………………………………26 ECM ref ground failures: a) Open circuit……………………………………………….27 b) Weak circuit………………………………………………28 ECM ref voltage: a) 5 Volt ref failures #1 (internal)……………………………29 b) 5 Volt ref failures #2 (internal)……………………………30 c) 5 Volt ref failures #3 (external)……………………………31 Ref Power Failures……………………………………………………...32 ECM communication: a) Communication lines……………………………………..33 b) Loss of Communication………………………………….34 ECM PROM..…………………………………………………………..35

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Moisture Damage……………………………………………………….36 ECM Failure…………………………………………………………….37 Coolant Temp Sensor: a) Operation…………………………………………………38 b) Harness failure……………………………………………39 c) Error #1…………………………………………………..40 d) Error #2…………………………………………………..41 Air Temp Sensor: a) Operation………………………………………………..42 b) Sensor failures…………………………………………..43-44 c) False sensor signal…..…………………………………..45 Throttle Position Sensor: a) Operation………………………………………………..46 b) TPS drop-out……………………………………………47 b) Throttle shaft wear………………………………………48 c) Clock indexing…………………………………………..49 d) Connector damage………………………………………50 ISC Position Sensor…………………………………………………….51 MAP Sensor: a) Linear Type……………………………………………..52 b) Frequency Type…………………………………………53 c) Sensor failure……………………………………………54 d) MAP line problems……………………………………..55 e) Mistaken Identity……………………………………….56 O2 Sensors: a) One-wire………………………………………………..57 b) Ref ground failure………………………………………58 c) Ref ground error…………………………………………59 d) True Lean operation……………………………………..60 e) False Lean operation…………………………………….61 f) Two-wire ………………………………………………..62 g) Isolated O2 Ground errors……………………………….63 h) Three-wire……………………………………………….64 i) Four-wire………………………………………………..65 j) Criss-Cross fuel control…………………………………66

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Knock Sensor…………………………………………………………..67 EGR Sensor: a) Temperature type…………………………………………68 b) Blocked EGR passage…………………………………….69 c) Lift sensor type……………………………………………70 d) Back-Pressure type………………………………………..71 e) PFE Damage………………………………………………72 f) Diagnostic Di i switch i h type…………………………………….73 73 Vane Air Flow sensor: a) Operation………………………………………………….74 b) Unmetered air……………………………………………..75 c) VAF door problems………………………………………..76 MAF sensor: a) Hot film type………………………………………………77 b) Hot film drop-out………………………………………….78 c) Hot-wire type………………………………………………79 d) Hot-wire contamination……………………………………80 e)) Hot-wire H t i failure f il #1 #1…………………………………………81 81 f) Hot-wire failure#2………………………………………….82 g) Frequency error………………………………………….83 ECM switches : a)Air Conditioning…………………………………………….84 b) Park/Neutral………………………………………………..85 Park/Neutral 85 c) Power Steering……………………………………………..86 Pick-Up coil: a) Operation…………………………………………………..87 b) Air Gaps……………………………………………………88 c) Weak AC signals….……………………………………….89 signals 89 d) Reverse polarity……………………………………………90 e) RPM drop-out……………………………………………..91 Crank Sensor: a) A/C output type……………………………………………92 b) Hall-Effect type……………………………………………93 type 93 c) Bad sensor signal…………………………………………..94

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CAM Sensor a) Operation Operation………………………………………………95 95 b) Erratic signal…………………………………………..96 Crank Angle Sensor: a) Operation………………………………………………97 b) RPM drop-outs…………………………………………98 c) Noise shields……………………………………………99 shields 99 IDM/Tach reference………………………………………………….100 RPM Specific signals…………………………………………………101-102 EMI/RFI problems……………………………………………………103-106 Vehicle Speed Sensor………………………………………………..107 Coil Drivers: a) Operation……………………………………………….108 b) Coil failures……………………………………………109-110 c) Driver failures………………………………………….111-112 d) Primary harness failures……………………………….113 p Timing: g Electronic Spark a) Operation……………………………………………….114 b) Failures…………………………………………………115 Injector Drivers: a) Peak and Hold type…………………………………….116 b)) Saturated type………………………………………….117 yp c) Injector Circuit Resistance……………………………..118 d) Loss of operation….…………………………………..119-120 e) Driver failures…………………………………………121 Quad driver circuits: p a)) Operation………………………………………….…..122 b) Driver circuit low #1………………………………….123 c) Driver circuit low #2………………………………….124 d) Failures……………………………………………….125 A/C Clutch relay……………………………………………………..126 Coolant Fan relay…………………………………………………….127 .

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EGR Solenoid: a) Operation…………………………………………………128 b) Failure…………………………………………………….129 Solenoid Control………………………………………………………130 IAC Solenoid…………………………………………………………..131 ISC Motor………………………………………………………………132 IAC Valve: a) Operation…………………………………………………133 b) Failure…………………………………………………….134 ECM Strategies: a) Closed/Open Loop………………………………………..135 b) Idle……………………………………………………….136 c) Fuel Enrichment………………………………………….137 d) Fuel Enleanment………………………………………….138 e) Cranking Enrichment……………………………………..139 f) Clear-Flood Mode…………………………………………140 g) Timing…………………………………………………….141-144 h) Power Management……………………………………….145-146 i) Back-Up……………………………………………………147 j) Speed Density………………………………………………148 System Monitors: a) Component…………………………………………………149 c) Misfire……………………………………………………..150 Performance Alterations…………………………………………………151-152 What’s here/What’s coming……………………………………………..153 List of Acronyms………………………………………………………..154-155 Note Pages……………………………………………………………….156-159

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My name is John Anello and my experience in the field is as follows: a) Gulf Service Center

-

Mechanic 1979-1980

b) Tune-up/Diagnostic Center -

Semi-Technician 1981-1982

c) Engine Rebuilding Shop

-

Rebuilder 1983-1985

d) Cadillac/Pontiac Dealer

-

Master Technician 1986-1991

e) Auto Tech On Wheels

-

Mobile Diagnostician 1991-present

I presently run a Mobile Diagnostic Center from which I provide technical assistance for about 1200 repair shops and 300 body shops in Northern NJ. My daily routine involves the diagnosis of many operating systems such as ABS, Air Bag, ECM, BCM and engine/electrical analysis. I also provide reprogramming of control modules and immobilizor systems on site.To this day I have diagnosed close to 50,000 vehicles of all makes and models. I also beta-test equipment for five major tool manufacturers so their tools can be fine-tuned to meet a technician’s requirements for real world application!

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Here is a prime example of a vehicle that could roll into your shop one day with a complaint that the engine just does not run well. You open the hood and start to raise your eye brows and notice that this vehicle not only has two distributors but also has a heat exchanger for a turbo that is no longer in use. This vehicle used to have a 1989 four cylinder turbo engine but a repair shop replaced the engine with a used 1985 four cylinder non-turbo engine and installed a 1989 non-turbo camshaft in the engine. The 1985 block had it’s own distributor but it would ld nott workk properly l with ith the th factory f t harness. h The Th shop h removedd the th camshaft and installed a 1989 camshaft that was coupled with a distributor that would adapt to the vehicle harness. The only problem was that the electronics were still the set designed for a turbo engine. The fix here was to replace the entire ECM and harness with a non-turbo one. Note: Visual N Vi l inspections i i are a key k to successful f l diagnostics. di i It I is i not uncommon in i the field to see cars that have been altered, sometimes considerably, from the original setup. These type of vehicles may not apply to normal troubleshooting tactics. It is up to a sharp tech who can see beyond theory and into the real world.

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It is very important to not become just a parts-replacer, basing your decisions on prior problems you fixed. What applies to one car may not always apply to another. You can have a similar problem causing the same results! You must have a game plan in order to tackle a problem. Provide yourself with the essentials: 1) Service bulletins and repair information, information 2) Proper diagnostic tools, 3) Proper education. It is also important to gather some background information on the car by talking to the customer. Verify the customer’s complaint even if you have to drive with him. You may drive differently from the way the customer does. Take time to read about system operation and to put the players (the components involved) on the board. Then find a test to rule out each player. By doing isolated tests you will narrow down the source of your problem and eliminate lost time as well as misdiagnosis.

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Prior to diagnosing a vehicle, it is important to speak to the driver and put him through an interrogation process that will allow you to properly fine-tune your diagnostic routine. You need to build yourself a list of basic test procedures prior to diagnosing a computer-related problem . Remember that engine performance will affect computer performance. Don’t overlook basic tests such as fuel pressure, compression, valve/ignition timing, exhaust back-pressure or even KV output at the sparkk plugs. l Make M k sure any test t t you perform f meets t the th specification ifi ti off the th manufacturer. Don’t use a generalized spec sheet! After your engine tests are performed satisfactorily, you will need to study the computer layout of the system. This will include all input sensors, output control devices as well as the ECM strategies. By doing so, you will give yourself a better understanding of the system you are working on and the ability to test each component to see whether it is working properly. properly

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The ECM is supplied with ground from the battery. There should never be more than 0.1 volt drop between the ECM and the battery. The ground source may be directly from the battery or indirectly from the engine block. During heavy electrical demands (A/C, coolant fan, wipers, rear defog, high beams, etc.), the ECM is always the smallest guy on the totem pole because it draws the least current. If the main engine ground is weak, the ECM will suffer and have either erratic EST operation or a total shift of its sensor operations. E Examples: l 1) Cadillac C dill bad b d engine i grounds--Erratic d E ti EST with ith A/C on. The ECM is also supplied with a constant battery positive feed. This feed allows the ECM to retain its memory of relearn strategies such as Idle Speed, Block Learn and Integrator. An ‘87 Mercury Cougar 3.8L turbo may keep running without its power feed but lose all operating strategies once the ignition is shut down. Another power supply is the ignition feed. The ignition is basically a wake-up call to the ECM to start system functions. This feed may come directly from the ignition switch or from a power relay energized by the ignition switch.

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The ECM takes the main ground and filters it to produce clean ref grounds for the sensors so they have noise-free redundant grounds. This prevents any noise on the sensor return signal lines to the ECM. These grounds should have no more than a 0.1 voltage drop. The ECM may also supply a shielding ground for dynamic signals such as cam, crank, and VSS sensors. This may aid in signal noise reduction by filtering the noise to ground through capacitors in the ECM. Once the ECM is awake, it produces ref voltage supply for the input sensors. The 5 volt ref is like the heartbeat of the ECM. Always check for a 5 volt ref to determine whether the ECM is functioning. The ECM monitors this voltage on the same ref line (for two-wire sensors) or the voltage return line (for three-wire sensors). y there mayy be other sensors sharingg the same 5 Note: In a three-wire 5 volt ref system volt supply. Often one defective sensor takes this 5 volt supply to ground and renders the other sensors inoperative. Examples: 1) Toyota no start 2) Ford no start

-- VAF Sensor VC circuit shorted to ground -- EGR PFE 5V circuit shorted to ground

3) GM lean operation -- CLS Sensor 5V circuit shorted to ground

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This vehicle had a hard-start/no-start condition and ran very poorly. By performing some checks on the sensor inputs, I found all the sensor values were higher than normal. The ECU had stored a code 1 for the O2 sensor and a code 16 for an injector circuit problem. The ref voltage was also out of range at 7.04 volts. Due to the high voltage readings, the grounds were my first area of concern. During a check of the grounds I found a high resistance in the ground circuit. Further inspection revealed a loose ECM ground at the thermostat housing. It had never b been properly l securedd after ft a simple i l thermostat th t t replacement. l t

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This 1987 Ford Mustang surged and stalled and kept setting a TPS code. The repair shop found the TPS out of spec and replaced it. The TPS was still not within spec so the shop elongated the TPS mounting holes to bring the TPS into spec. This did not resolve the problem. When the TPS harness was checked, it was discovered that the reference voltage was at 5.73 volts and the reference ground had a voltage drop of about 0.71 volts. The ECM was still regulating it’s 5 volt supply, but because the reference ground was bad b d it allowed ll d a hi higher h operating ti window. i d Thi This was the th result lt off the th higher hi h than th normal TPS reading. The ECM also had a bad ground at the battery which created weak reference ground output feeds to all the sensors. Note: It is important to fully understand sensor feeds and how to perform basic electrical checks prior to any component replacement.This could prevent unnecessary parts replacement. l

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This Taurus had a cooling fan sharing the same ground feed with the ECM. The connector developed high resistance, which caused the connector to overheat and melt. This set up an intermittent no-start condition with no spark and no fuel pulse whenever the ECM ground became weak. Make visual inspections a central part of your diagnosis! Sometimes the bad ground is mechanic mechanic-induced induced. II’ve ve seen cars where during a battery replacement someone took the ECM ground for a fusible link and connected it directly to the positive post! This would reverse bias the ECM and cause damage to its internal board.

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This is a bad ground cable that shows a high resistance to current flow. Visual inspections are always necessary during diagnostics. Basic electrical tests can really help cut down on unneeded parts replacement: a) Starter draw tests -- 1 amp per cubic inch of cylinder displacement, b) Cranking voltage test -- 9.6 volts or better (some manufacturers may be higher), c) Voltage drop test -- No more then 0.3 volts at the ECM while cranking. To check ECM grounds, load the circuits by turning all the accessories on while the engine is running. Every ground gains resistance under load, and the largest current gets the best ground. “The big guy always gets the pie!�

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This vehicle ran erratically at times during high electrical loads. The EST operation got so bad that the car backfired and bucked on acceleration. If the ignition system was placed in base timing mode by opening the bypass line, the problem went away because the ECM no longer controlled coil triggering. With a scope you can see the grounds lift for fractions of a second, causing a total shutdown of ECM injector or coil triggering. The ECM grounds had a poor contact at the block, so I removed and cleaned them all, reconnected them using star washers, h andd thus th solved l d the th erratic ti running i problems. bl

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This picture shows a poor connection performed by a garage in an attempt to repair a burnt ECM power feed line. This connection would make and break and cause an intermittent no start accompanied by a loss of communication with a scan tool. The proper fix was to repair the harness with a proper fusible link, a section of wire two gauge sizes smaller (two wire-gauge numbers higher) than the rest of the power feed wire.

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This vehicle had a no-start/no-spark/no-fuel-pulse condition caused by a blown fusible link. This also left the ECM with a memory loss. The garage repaired both blown fuse links by mating them together. This only compounded the original problem, and the technician went on to replace the ECU unnecessarily.

Note: Proper fuse link repairs require the replacement fuse link to be two gauge sizes lower (two wire sizes higher) than the main wire to the circuit it protects.

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