Advanced Automotive Fault Diagnosis

Automotive Technology: Vehicle Maintenance and Repair

Tom Denton

• Publisher: Routledge
• Year: 2020
• ISBN:
  9781000178388
• Edition: 5
• Topic: Technology & Engineering
• Subtopic: Automotive Transportation & Engineering
• Index: Technology & Engineering

Diagnostics: Test don't guess.

Learn all the skills you need to pass Level 3 and 4 Vehicle Diagnostics courses from IMI, City & Guilds, and BTEC, as well as ASE, AUR, and other higher-level qualifications.

Along with 25 new real-life case studies, this fifth edition of Advanced Automotive Fault Diagnosis includes new content on diagnostic tools and equipment: VCDS, decade boxes, scanners, pass through, sensor simulators, break out boxes, multimeter updates for HV use, and more. It explains the fundamentals of vehicle systems and components, and it examines diagnostic principles and the latest techniques employed in effective vehicle maintenance and repair. Diagnostics, or faultfinding, is an essential part of an automotive technician's work, and as automotive systems become increasingly complex there is a greater need for good diagnostic skills.

Ideal for students, included throughout the text are useful definitions, key facts, and 'safety first' notes. This text will also assist experienced technicians to further improve their performance and keep up with recent industry developments.

Chapter 1

Introduction

1.1Diagnosis

1.1.1What is needed to find faults?

Finding the problem when complex automotive systems go wrong is easy if you have the necessary knowledge. This knowledge consists of two parts:

• understanding of the system in which the problem exists;
• the ability to apply a logical diagnostic routine.

It is also important to be clear about these definitions:

• symptom(s) – what the user/operator/repairer of the system (vehicle or whatever) notices;
• fault(s) – the error(s) in the system that result in the symptom(s);
• root cause(s) – the cause(s) of the fault.

If a system is not operating to its optimum, then it should be repaired. This is where diagnostic and other skills come into play. It is necessary to recognise that something is not operating correctly by applying your knowledge of the system, and then by applying this knowledge further and combining it with the skills of diagnostics to be able to find out the reason.

Definition

Diagnostics: The word ‘diagnostics' centres around the principle of the four rights: Measuring the right thing, in the right way, at the right time, with the right tool. (Source: TechTopics, www.techtopics.co.uk)

The four main chapters of this book (‘Engine systems’, ‘Chassis systems’, ‘Electrical systems’ and ‘Transmission systems’) include a basic explanation of the vehicle systems followed by diagnostic techniques that are particularly appropriate for that area. Examples of faultfinding charts are also included. In the main text, references will be made to generic systems rather than to specific vehicles or marques. For specific details about a particular vehicle or system, the manufacturer’s information is the main source.

Definition

Diagnosis: The word ‘diagnosis’ comes from the ancient Greek word ‘δια′γνωσις’, which means discernment. It is the identification of the nature and cause of anything. Diagnosis is used in many different disciplines, but all use logic, analysis and experience to determine cause and effect relationships. In automotive engineering, diagnosis is typically used to determine the causes of symptoms and solutions to issues.

Key Fact

General diagnostic principles and techniques can be applied to any system, physical or otherwise.

Other chapters such as ‘Sensors, actuators and oscilloscope diagnostics’ and ‘On-board diagnostics’ are separated from the four previously mentioned chapters, because many operations are the same. For example, testing an inductive sensor is similar whether it is used on ABS or engine management.

An important note about diagnostics is that the general principles and techniques can be applied to any system, physical or otherwise. As far as passenger-carrying heavy or light vehicles are concerned, this is definitely the case. As discussed earlier, there is a need for knowledge of the particular system, but diagnostic skills are transferable (Figure 1.1).

Figure 1.1 Diagnostics in action.

1.2Safe Working Practices

1.2.1Introduction

Safe working practices in relation to diagnostic procedures, and indeed any work on a vehicle, are essential – for your safety as well as that of others. You only have to follow two rules to be safe:

Use your common sense – do not fool about. If in doubt – seek help.

Further, always wear appropriate personal protective equipment (PPE) when working on vehicles.

The following section lists some particular risks when working with vehicle systems, together with suggestions for reducing them. This is known as risk assessment.

Safety First

Aways wear appropriate personal protective equipment (PPE) when working on vehicles.

1.2.2Risk assessment and reduction

Table 1.1 lists some identified risks involved with working on vehicles. The table is by no means exhaustive but serves as a good guide.

Table 1.1 Identifying and reducing risk

Identified risk	Reducing the risk
Battery acid	Sulphuric acid is corrosive, so always use good PPE – in this case overalls and if necessary rubber gloves. A rubber apron is ideal as are goggles if working with batteries a lot, particularly older types.
Electric shock	Ignition HT is the most likely place to suffer a shock – up to 25000V is quite normal. Use insulated tools if it is necessary to work on HT circuits with the engine running. Note that high voltages are also present on circuits containing windings due to back emf as they are switched off – a few hundred volts is common. Mains supplied power tools and their leads should be in good condition, and using an earth leakage trip is highly recommended.
Exhaust gases	Suitable extraction must be used if the engine is running indoors. Remember it is not just the CO that might make you ill or even kill you, other exhaust components could also cause asthma o...