«Allan W. M. Bonnick MPhil CEng MIMechE MIRTE OXFORD AUCKLAND BOSTON JOHANNESBURG MELBOURNE NEW DELHI Butterworth-Heinemann Linacre House, Jordan ...»
Diagnostic tools and techniques
Allan W. M. Bonnick
MPhil CEng MIMechE MIRTE
OXFORD AUCKLAND BOSTON JOHANNESBURG MELBOURNE NEW DELHI
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 629.20 549 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.
ISBN 0 7506 5089 3
1. Automotive computers. 2. Automobiles – Maintenance and repair. I. Title.
TL272.53 B66 629.20 7 – dc21 2001018080 Typeset in 11/13pt Garamond by Laser Words, Madras, India Printed and bound in Great Britain 1 Common technology
1.1 Common technology
1.2 Engine-related systems
1.3 Ignition systems
1.3.1 THE CONSTANT ENERGY IGNITION SYSTEM
1.3.2 DIGITAL (PROGRAMMED) IGNITION SYSTEM
1.3.3 DISTRIBUTORLESS IGNITION SYSTEM...... 6 1.3.4 OPTOELECTRONIC SENSING FOR THE IGNITION SYSTEM
1.3.5 KNOCK SENSING
1.3.6 ADAPTIVE IGNITION
1.4 Computer controlled petrol fuelling systems..... 10 1.4.1
7 Diagnostic techniques
7.1 Circuit testing
7.2 Vehicle specific details
7.3 The ’six-steps’ approach
7.4 Skills required for effective diagnosis............... 174
7.5 An approach to fault finding
7.6 Emissions related testing
7.6.1 OXYGEN SENSOR
7.6.2 KNOCK SENSORS
7.6.3 AIR FLOW METERS
7.6.4 THROTTLE POSITION SWITCHES............... 190 7.6.5 A COOLANT TEMPERATURE SENSOR....... 192 7.6.6 MANIFOLD ABSOLUTE PRESSURE SENSOR (MAP) TESTS
7.7 Ignition system tests
7.7.1 TESTS ON DISTRIBUTORLESS IGNITION DIS
7.8 Diesel injection
7.8.1 TESTING THE INJECTION POINT ADVANCE
7.9 Sensor tests on other systems
7.9.1 ABS WHEEL SPEED SENSORS
7.9.2 TESTING THE RIDE HEIGHT CONTROL SENSOR
7.10 Intermittent faults
7.10.1 FLIGHT RECORDER (DATA LOGGER) FUNCTION
7.12 Review questions
A.1 Companies who supply equipment and diagnostic data
A.2 Answers to review questions
A.3 OBD II standard fault codes
Improvements in design, materials and manufacturing techniques have combined to produce vehicles that are, in general, very reliable. Many servicing and repair tasks, such as rebores, big-end repairs, gearbox overhauls etc., are no longer commonplace and this sometimes gives the impression that today’s vehicle technicians 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 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 emission system may be malfunctioning and a ﬁrst reaction might be that the exhaust catalyst has failed. But what about other factors, such as air ﬁlter, fuel pressure, condition of the injectors, condition of the ignition system, engine valves, cylinder compression etc.? I have assumed that most readers of this book will be engaged in vehicle service work, in training or education and that they will have knowledge of the basic technology and science that enables them to ‘think through’ the connections between defects in computer controlled systems and the factors that may 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 petrol engines 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 similar and 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 broadly similar principles and this makes them amenable to testing by means that are widely available. When an object, such as a sensor, bears similar properties to other objects it may be referred to as belonging to a genus and the term ‘generic testing’ 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 now making equipment that enables technicians to perform a wide range 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 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 3, BTEC National Certiﬁcate and Diploma, Higher National 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 in computing, may also ﬁnd the book helpful in obtaining a better understanding about their own vehicles, particularly in relation to features such as the European OBD, which is likely to cause widespread attention when it becomes more widely used in the UK.
Allan Bonnick Acknowledgements
Thanks are due to the following companies who supplied information and in many 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 SAE J 2012 MAR99 1999) Toyota Motor Company Volvo Cars Wabco Special thanks also to Shirley and to Phil Handley who persuaded me that the effort was worthwhile, especially when the going was hard.
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 work across the spectrum of vehicles, from small cars to heavy trucks.
Subsequent chapters concentrate on aspects of the technology that enable garage technicians to perform diagnostic and other tasks related to the maintenance and repair of modern vehicles. In order to achieve this aim a representative range of systems is examined in outline, so as to give a broad understanding of their construction and mode of operation, as opposed to an ‘in depth’ study of each system. Later chapters look at the individual aspects of each system, such as sensors and the computer (ECM), and provide detailed explanations since the evidence suggests that more detailed knowledge assists in the diagnostic process.
1.1 Common technology Changes in electronics technology and manufacturing methods take place rapidly and 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 and presumably 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 as the Electronic Control Module (ECM). In this book, the term electronic control module (ECM) is used when referring to the control module that was formerly known as the ECU.
As vehicle systems have developed it has become evident that there is a good deal of electronic and computing technology that is common to many vehicle electronic systems and this suggests that there is good reason for technicians to learn this ‘common technology’ because it should enable them to tackle diagnosis and repair on a range of vehicles. Indeed, many manufacturers of automotive test 2 Common technology equipment are now producing equipment which, when supported by information and data about diagnostic trouble codes (fault codes), provides the knowledgeable technician with the support that should enable him/her to go forward 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, plus emission control. A major purpose of these system 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 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 that are used on vehicles. In effect, there is a good deal of knowledge that can 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 ‘on and 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 the ignition, but three of these methods are more widely used than the others. It is the ignition systems that are based on the use of these three methods that are now dealt with in some detail.
1.3.1 THE CONSTANT ENERGY IGNITION SYSTEMFigure 1.1 shows a type of electronic ignition distributor that has been in use for many years. The distributor shaft is driven from the engine camshaft and thus rotates 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 is connected to the electronic ignition module and when the pulse generator voltage has reached a certain level (approximately 1 V) the electronic circuit of the module will switch on the current to the ignition coil primary winding.
Ignition systems 3
Fig. 1.1 Reluctor and pick-up assembly