Automotive Computer Controlled Systems Diagnostic tools and techniquesAllan W.. 30 1.11 Computer controlled diesel engine management systems ..... I have assumed that most readers of thi
Trang 2Automotive Computer Controlled Systems
Trang 3Automotive Computer Controlled Systems Diagnostic tools and techniques
Allan W M Bonnick
MPhil CEng MIMechE MIRTE
OXFORD AUCKLAND BOSTON JOHANNESBURG MELBOURNE NEW DELHI
Trang 4Linacre 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
Typeset in 11/13pt Garamond by Laser Words, Madras, India
Printed and bound in Great Britain
Trang 51 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
Trang 61.13 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
Trang 73 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
Trang 85.1.1 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
Trang 96.4.1 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
Trang 107.10.1 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
Trang 11A.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
Trang 12Improvements in design, materials and manufacturing techniques have combined
to produce vehicles that are, in general, very reliable Many servicing and repairtasks, such as rebores, big-end repairs, gearbox overhauls etc., are no longercommonplace and this sometimes gives the impression that today’s vehicletechnicians do not need the range of skills that once were necessary
It may be the case that the so called ‘traditional’ skills are less important, but thechange in automotive technology that has resulted from the introduction of manycomputer controlled systems has meant that technicians require additional skills.These additional skills are discussed However, it remains the case that techniciansneed to have a thorough understanding of technical and scientific principles thatlie behind the operation of vehicle systems For example, an exhaust emissionsystem may be malfunctioning and a first reaction might be that the exhaustcatalyst has failed But what about other factors, such as air filter, fuel pressure,condition of the injectors, condition of the ignition system, engine valves, cylindercompression etc.? I have assumed that most readers of this book will be engaged invehicle service work, in training or education and that they will have knowledge
of the basic technology and science that enables them to ‘think through’ theconnections between defects in computer controlled systems and the factors thatmay be contributing to them
The text concentrates on areas of technology that are common to a range
of systems For example, air flow meters are a common feature on most petrolengines and they are of two types: volumetric flow (the flap), and mass flow such
as the hot wire and the hot film The outputs from these sensors are broadly similarand they can be measured accurately with the type of equipment that is described.Most exhaust gas oxygen sensors are of the zirconia type and the output signals,
on almost all vehicles to which they are fitted, will be broadly identical
There are families or groups of sensors and actuators that operate on broadlysimilar principles and this makes them amenable to testing by means that arewidely available When an object, such as a sensor, bears similar properties toother objects it may be referred to as belonging to a genus and the term ‘generictesting’ is sometimes used since the tests can be applied to most, if not all,
of the same type of sensor Many diagnostic equipment manufacturers are nowmaking equipment that enables technicians to perform a wide range of tests oncomputer controlled systems The aim of this book is to show how, with the aid
Trang 13x Preface
of equipment, suitable training and personal endeavour, service technicians andtrainees 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 be used to perform effective diagnosis on a range
of computer controlled systems Also covered is a range of modern computercontrolled systems, computer technology and features such as CAN and OBD II.This book has been designed to meet the needs of students and trainees whoare working for NVQ level 3, BTEC National Certificate and Diploma, HigherNational and similar vocational qualifications However, the treatment of topics
is sufficiently broad as to provide useful background knowledge for students
of design and technology, and those on computing courses who are studying
in schools and colleges DIY motorists, particularly those with an interest incomputing, may also find the book helpful in obtaining a better understandingabout their own vehicles, particularly in relation to features such as the EuropeanOBD, which is likely to cause widespread attention when it becomes more widelyused in the UK
Allan Bonnick
Trang 14Thanks are due to the following companies who supplied information and inmany cases permission to reproduce illustrations
Crypton Technology Group
Ford Motor Company
Fluke (UK) Ltd
Gunson Limited
Lucas Aftermarket Operations Ltd
Lucas Diesel Systems
Lucas Varity Ltd
Motorola
Renault Ltd
Robert Bosch Ltd (Mr Richard Clayton – Garage equipment dept.)
Rover Car Company
Society of Automotive Engineers, Inc (Reprinted with permission from
Trang 15Common technology
The aim of this chapter is to review a number of computer controlled vehiclesystems that are in current use and to make an assessment of the technologyinvolved 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 skillsthat will assist in diagnostic work across the spectrum of vehicles, from small cars
to heavy trucks
Subsequent chapters concentrate on aspects of the technology that enablegarage technicians to perform diagnostic and other tasks related to the mainten-ance and repair of modern vehicles In order to achieve this aim a representativerange of systems is examined in outline, so as to give a broad understanding oftheir construction and mode of operation, as opposed to an ‘in depth’ study ofeach system Later chapters look at the individual aspects of each system, such
as sensors and the computer (ECM), and provide detailed explanations since theevidence suggests that more detailed knowledge assists in the diagnostic process
1.1 Common technology
Changes in electronics technology and manufacturing methods take place rapidlyand for some years now, microcontrollers (mini-computers) have formed the heart
of many of the control systems found on motor vehicles
Microcontrollers, in common with other computers, contain a control unit andpresumably in order to avoid any possible confusion, the ‘black box’ that used to
be known as the Electronic Control Unit (ECU) is now commonly referred to asthe Electronic Control Module (ECM) In this book, the term electronic controlmodule (ECM) is used when referring to the control module that was formerlyknown as the ECU
As vehicle systems have developed it has become evident that there is a gooddeal of electronic and computing technology that is common to many vehicleelectronic systems and this suggests that there is good reason for technicians tolearn this ‘common technology’ because it should enable them to tackle diagnosisand repair on a range of vehicles Indeed, many manufacturers of automotive test
Trang 162 Common technology
equipment are now producing equipment which, when supported by informationand data about diagnostic trouble codes (fault codes), provides the knowledgeabletechnician with the support that should enable him/her to go forward in to the2000s with a degree of confidence in their ability to maintain and repair modernsystems
We will now look at a representative selection of commonly used modernsystems in order to enable us to ‘tease out’ the common elements that it will beuseful 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, plus emission control A major purpose of thesesystem surveys is to identify common ground in order to focus on the components
of the systems that can realistically be tested with the aid of reasonably pricedtools, rather than the more exotic systems that require specialized test equipment
By examining three ignition systems it should be possible to pick out certainelements that are commonly used In the process of examining a number of othersystems we shall see that certain basic principles are common to several types ofsystems that are used on vehicles In effect, there is a good deal of knowledge thatcan be transferred across a considerable range of technology
1.3 Ignition systems
Electronic ignition systems make use of some form of electrical/electronic device
to produce the electrical pulse that switches the ignition coil primary current ‘onand off ’, so that a high voltage is induced in the coil secondary winding in order
to produce a spark in the required cylinder at the correct time
There are several methods of producing the basic ‘triggering’ pulse for theignition, but three of these methods are more widely used than the others It isthe ignition systems that are based on the use of these three methods that are nowdealt with in some detail
1.3.1 THE CONSTANT ENERGY IGNITION SYSTEM
Figure 1.1 shows a type of electronic ignition distributor that has been in use formany years The distributor shaft is driven from the engine camshaft and thusrotates at half engine speed
Each time a lobe on the rotor (reluctor) passes the pick-up probe a pulse
of electrical energy is induced in the pick-up winding The pick-up winding isconnected to the electronic ignition module and when the pulse generator voltagehas reached a certain level (approximately 1 V) the electronic circuit of the modulewill switch on the current to the ignition coil primary winding