Automotive Computer Controlled Systems Automotive Computer Controlled Systems Diagnostic tools and techniques Allan W. M. Bonnick MPhil CEng MIMechE MIRTE OXFORD AUCKLAND BOSTON JOHANNESBURG MELBOURNE NEW DELHI Butterworth-Heinemann Linacre House, Jordan Hill, Oxford OX2 8DP 225 Wildwood Avenue, Woburn, MA 01801-2041 A division of Reed Educational and Professional Publishing Ltd First published 2001  Allan Bonnick, 2001 All rights reserved. No part of this publication may be reproduced in any material form (including photocopying or storing in any medium by electronic means and whether or not transiently or incidentally to some other use of this publication) without the written permission of the copyright holder except in accordance with the provisions of the Copyright, Designs and Patents Act 1988 or under the terms of a licence issued by the Copyright Licensing Agency Ltd, 90 Tottenham Court Road, London, England W1P 0LP. Applications for the copyright holder’s written permission to reproduce any part of this publication should be addressed to the publishers British Library Cataloguing in Publication Data Bonnick, Allan W.M. Automotive computer controlled systems: diagnostic tools and techniques 1. Automotive computers I. Title 629.2 0 549 ISBN 0 7506 5089 3 Library of Congress Cataloguing in Publication Data Bonnick, Allan W.M. Automotive computer controlled systems: diagnostic tools and techniques/Allan W.M. Bonnick. p.cm. Includes index. ISBN 0 7506 5089 3 1. Automotive computers. 2. Automobiles – Maintenance and repair. I. Title. TL272.53 B66 629.2 0 7 – dc21 2001018080 Typeset in 11/13pt Garamond by Laser Words, Madras, India PrintedandboundinGreatBritain 1 Common technology 1 1.1 Common technology 1 1.2 Engine-related systems 2 1.3 Ignition systems 2 1.3.1 THE CONSTANT ENERGY IGNITION SYSTEM 2 1.3.2 DIGITAL (PROGRAMMED) IGNITION SYSTEM 3 1.3.3 DISTRIBUTORLESS IGNITION SYSTEM 6 1.3.4 OPTOELECTRONIC SENSING FOR THE IGNITION SYSTEM 8 1.3.5 KNOCK SENSING 9 1.3.6 ADAPTIVE IGNITION 9 1.4 Computer controlled petrol fuelling systems 10 1.4.1 SINGLE-POINT INJECTION 11 1.4.2 MULTI-POINT INJECTION 13 1.5 Engine management systems (EMS) 17 1.5.1 EXHAUST GAS RECIRCULATION 18 1.5.2 COMPUTER CONTROL OF EVAPORATIVE EMISSIONS 19 1.6 Anti-lock braking (ABS) 19 1.6.1 OPERATION OF ABS 22 1.6.2 SOME GENERAL POINTS ABOUT ABS 22 1.7 Traction control 22 1.8 Stability control 25 1.9 Air conditioning 27 1.9.1 DEALING WITH AIR CONDITIONING REFRIGERANT 29 1.10 Computer controlled damping rate 30 1.11 Computer controlled diesel engine management systems 30 1.11.1 SPILL CONTROL 33 1.11.2 TIMING CONTROL 35 1.11.3 IDLE SPEED CONTROL 35 1.12 Summary 38 1.13 Review questions 38 2 The Computer ECM 2 2.1 The fundamental parts of a computer 2 2.1.1 COMPUTER MEMORY 41 2.1.2 THE CLOCK 41 2.2 A practical automotive computer system 41 2.3 Principles of operation 44 2.4 Computer data 45 2.4.1 DATA TRANSFERS 45 2.4.2 DATA TRANSFER REQUIREMENTS 46 2.5 Computer interfaces 46 2.6 Control of output devices 47 2.7 Computer memories 48 2.7.1 READ ONLY MEMORIES 49 2.7.2 RANDOM ACCESS MEMORY 50 2.7.3 OTHER TYPES OF COMPUTER MEMORY 50 2.8 Fault codes 51 2.9 Adaptive operating strategy of the ECM 51 2.9.1 LIMITED OPERATING STRATEGY (LOS) 52 2.10 Networking of computers 52 2.10.1 A BUS-BASED SYSTEM 52 2.10.2 STAR CONNECTED COMPUTERS 52 2.10.3 MESSAGES 53 2.10.4 PROTOCOLS 54 2.11 Vehicle network systems 55 2.11.1 THE PRINCIPLE OF A BUS-BASED VEHICLE SYSTEM 55 2.11.2 DATA BUSES FOR DIFFERENT APPLICATIONS 57 2.11.3 ENCODING SERIAL DATA 57 2.12 Prototype network systems 59 2.13 Summary 62 2.14 Review questions 63 3 Self-diagnosis and fault codes 3 3.1 Access to DTCs 3 3.1.1 METHOD 1: THE DASHBOARD LAMP 4 3.1.2 METHOD 2: FAULT CODES DISPLAYED THROUGH A LOGIC PROBE OR TEST LAMP 70 3.1.3 METHOD 3: FAULT CODE READERS AND SCAN TOOLS 70 3.2 Developments in self-diagnosis 78 3.2.1 OBD I 79 3.2.2 OBD II 79 3.3 Diagnostic equipment and limitations of DTCs 3.22 3.4 Review questions 83 4 Diagnostic tools and equipment 4 4.2 Breakout boxes 94 4.1 Diagnostic tools that connect to ECM 4 4.3 The digital multimeter 95 4.4 Portable flat screen oscilloscopes 96 4.5 Diagnostic tool and oscilloscope combined 97 4.6 Pressure gauges 99 4.6.1 VACUUM PUMPS AND GAUGES 99 4.7 Calibrating test instruments 103 4.8 Location charts and wiring diagrams 103 4.9 Sources of diagnostic data 103 4.10 Exhaust gas emissions and emission system testing 4.21 4.10.1 PETROL ENGINE EMISSIONS 4.21 4.10.2 DIESEL ENGINE EMISSIONS 108 4.11 Review questions 110 5 Sensors 5 5.1 Electromagnetic sensors 5 5.1.1 THE VARIABLE RELUCTANCE TYPE SENSOR 5 5.1.2 HALL EFFECT SENSORS 116 5.2 Optical sensors 118 5.3 Combustion knock sensors 119 5.4 Variable resistance type sensors 121 5.5 Temperature sensors 124 5.6 Ride height control sensor 125 5.7 Manifold absolute pressure (MAP) 126 5.7.1 THE VARIABLE VOLTAGE MAP SENSOR 127 5.7.2 OTHER MAP SENSORS 129 5.8 Exhaust gas oxygen sensors 130 5.8.1 THE VOLTAIC-TYPE EGO SENSOR 132 5.8.2 THE RESISTIVE-TYPE EGO SENSOR 137 5.8.3 ON-BOARD MONITORING OF THE CATALYTIC CONVERTER 138 5.9 Air flow measurement 138 5.9.1 HOT WIRE MASS AIR FLOW SENSOR (MAF) 142 5.10 The practical importance of sensor knowledge 144 5.11 Review questions 144 6 Actuators 6 6.1 Actuator operation 6 6.2 Petrol engine fuel injectors 147 6.2.1 SINGLE POINT INJECTION 147 6.2.2 MULTI-POINT PETROL INJECTION 147 6.3 Testing of petrol injectors 149 6.3.1 PEAK AND HOLD 149 6.3.2 CONVENTIONAL SWITCHING TO EARTH 150 6.3.3 PULSE WIDTH MODULATED INJECTORS 152 6.3.4 FURTHER INJECTOR TESTS 154 6.4 Exhaust gas recirculation 154 6.4.1 TESTING THE EGR SENSOR 155 6.5 Petrol engine idle speed control 155 6.5.1 STEPPER MOTOR-OPERATED VALVE 157 6.5.2 SOLENOID-OPERATED VALVE 160 6.6 Ignition system 161 6.7 ABS actuators 161 6.8 A clamping diode 162 6.9 Electronic unit injectors 163 6.10 Review questions 165 7 Diagnostic techniques 7 7.1 Circuit testing 7 7.2 Vehicle specific details 172 7.3 The ’six-steps’ approach 173 7.4 Skills required for effective diagnosis 174 7.5 An approach to fault finding 175 7.6 Emissions related testing 179 7.6.1 OXYGEN SENSOR 179 7.6.2 KNOCK SENSORS 186 7.6.3 AIR FLOW METERS 187 7.6.4 THROTTLE POSITION SWITCHES 190 7.6.5 A COOLANT TEMPERATURE SENSOR 192 7.6.6 MANIFOLD ABSOLUTE PRESSURE SENSOR (MAP) TESTS 195 7.7 Ignition system tests 198 7.7.1 TESTS ON DISTRIBUTORLESS IGNITION DIS 198 7.8 Diesel injection 200 7.8.1 TESTING THE INJECTION POINT ADVANCE 202 7.9 Sensor tests on other systems 202 7.9.1 ABS WHEEL SPEED SENSORS 203 7.9.2 TESTING THE RIDE HEIGHT CONTROL SENSOR 206 7.10 Intermittent faults 207 7.10.1 FLIGHT RECORDER (DATA LOGGER) FUNCTION 208 7.11 Summary 209 7.12 Review questions 210 8 Additional technology 8 8.1 Partial and absolute pressures 8 8.2 The piezoelectric effect 213 8.3 Liquid crystal displays 214 8.4 Countering cross-talk 216 8.5 Logic devices 216 8.5.1 THE RTL NOR GATE 216 8.5.2 TRUTH TABLES 217 8.5.3 THE SR (SET, RESET) FLIP-FLOP 218 8.5.4 ANALOGUE TO DIGITAL CONVERSION 221 8.5.5 DIGITAL TO ANALOGUE CONVERSION 222 8.6 OBD II 223 8.6.1 FUEL SYSTEM LEAKAGE 224 8.6.2 SECONDARY AIR INJECTION 225 8.6.3 FREEZE FRAMES 226 8.6.4 STANDARDIZED FAULT CODES 226 8.7 Computer performance (MIPS) 227 8.8 Supplementary restraint systems (SRS) 227 8.8.1 HANDLING SRS COMPONENTS 230 8.9 The coded ignition key 231 8.10 Fault tracing 232 8.11 Precautions when working with computer controlled systems 232 8.12 Variable capacitance sensor 233 8.13 Optoelectronics 234 8.14 Review questions 235 Appendix A.1 A.1 Companies who supply equipment and diagnostic data A.1 A.2 Answers to review questions A.1 A.3 OBD II standard fault codes 238 Index 46 [...]... knock sensor, and a manifold pressure sensor for indicating engine load In the next section, computer controlled fuelling systems are examined and it will be seen that quite a lot of the technology is similar to that used in electronic ignition systems 1.4 Computer controlled petrol fuelling systems Computer controlled petrol injection is now the normal method of supplying fuel – in a combustible mixture... repair Chapters 5, 6 and 7 show how knowledge of the technology that is common to many of the systems can be used to perform effective diagnosis on a range of computer controlled systems Also covered is a range of modern computer controlled systems, computer technology and features such as CAN and OBD II This book has been designed to meet the needs of students and trainees who are working for NVQ level... especially when the going was hard 1 Common technology The aim of this chapter is to review a number of computer controlled vehicle systems that are in current use and to make an assessment of the technology involved that is common to a range of systems It is this knowledge that is ‘common’ to many systems that enables a vehicle technician to develop a ‘platform’ of skills that will assist in diagnostic... the systems that can realistically be tested with the aid of reasonably priced tools, rather than the more exotic systems that require specialized test equipment By examining three ignition systems it should be possible to pick out certain elements that are commonly used In the process of examining a number of other systems we shall see that certain basic principles are common to several types of systems. .. extensively on computer controlled systems and it requires technicians to run vehicles under normal driving conditions for several minutes after replacement parts and adjustments have been made to a vehicle This review of ignition systems gives a broad indication of the technology involved and, more importantly, it highlights certain features that can reasonably be said to be common to all ignition systems. .. important, but the change in automotive technology that has resulted from the introduction of many computer controlled systems has meant that technicians require additional skills These additional skills are discussed However, it remains the case that technicians need to have a thorough understanding of technical and scientific principles that lie behind the operation of vehicle systems For example, an exhaust... order that the computer can determine the duration of the fuel injection pulse Some computerized systems are designed so that the franchised dealership can alter the computer program to match customer requirements A re-programmable ROM is necessary for this to be done and the work can only be done by qualified personnel acting under the control of the vehicle manufacturer Multi-point injection systems commonly... output voltage at low and high speeds Fig 1.3 A digital ignition system Ignition systems 5 The control unit (ECU or ECM) is a small, dedicated computer which has the ability to read input signals from the engine, such as speed, crank position, and load These readings are compared with data stored in the computer memory and the computer then sends outputs to the ignition system It is traditional to represent... of tests on computer controlled systems The aim of this book is to show how, with the aid x Preface of equipment, suitable training and personal endeavour, service technicians and trainees may equip themselves with the knowledge and skill that will permit them to perform accurate diagnosis and repair Chapters 5, 6 and 7 show how knowledge of the technology that is common to many of the systems can... in to the 2000s with a degree of confidence in their ability to maintain and repair modern systems We will now look at a representative selection of commonly used modern systems in order to enable us to ‘tease out’ the common elements that it will be useful to learn more about 1.2 Engine-related systems The engine systems that are surveyed are those that are most commonly used, namely ignition and fuelling, . Automotive Computer Controlled Systems Automotive Computer Controlled Systems Diagnostic tools and techniques Allan. the systems can be used to perform effective diagnosis on a range of computer controlled systems. Also covered is a range of modern computer controlled systems,