[...]... 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, .