Petrol engine

management diagnostics

Wednesday 15th September 2010

The aim of this page is to form the basis for a series of articles from AK Automotive explaining the processes involved when diagnosing faults with modern petrol engine management systems. It is intended as a guide and to offer some helpful tips and advice to try and make life easier.

Preliminary measures: background knowledge and liaising with customers

No two faults are the same and every diagnosis should be started with due regard for all factors that could have an affect. Keep an open mind. Formulating effective diagnostic strategies requires detailed background knowledge and experience of system operating principles.

The most important thing is to understand and be able to evaluate fault symptoms and effectively gather evidence and information relating to the fault. The starting point for any diagnosis should therefore always be the customer.

A very important thing to bear in mind is whether the problem has been looked at before. Picking up the pieces from somebody else’s work is very difficult.

Be wary of spurious, unrelated faults that have been induced into the system through inappropriate tests carried out by other people. Typical additional problems include disconnecting components whilst the ignition is switched on which induces more fault codes into the system.

When liaising with the customer, typical questions to ask are:

• When did the fault occur?
• Where did the fault occur (for example on a particular piece of road, going up/down a hill, during cornering/braking etc)?
• How often has the fault occurred?
• What are the conditions when the fault occurs (engine hot/cold, during overrun or acceleration, first thing in the morning, after a period of driving etc).
• Are any warning lamps illuminated in the instrument cluster (dash panel)?
• What is the service history of the vehicle?
• Has any other work been done to the vehicle recently (for example a body shop or other mechanical/electrical repair)?
  

Further information

The petrol engine management course from AK Automotive is a two day practical diagnostics course. Click here for details about the course For enquiries and to book a place on the course, contact: Tony Kitchen MIMI (AK Automotive) Telephone: 01908 579309 Mobile: 07968 842274 Click here to contact AK Automotive Mobile e-mail: tony.ak@blackberry.orange.co.uk

Ask probing questions and let the customer describe the fault symptoms in their own words. Make notes where appropriate and clarify any points with the customer that you don’t understand.

A road test with the customer, where practicable, is essential to experience the symptoms first hand. Also, you need to understand the customer and be clear about their expectations, motives and what work they actually want you to do on their vehicle.

When the initial consultation with the customer is complete, it is time to get down to deciding what physical checks and diagnostic tests need to be carried out.

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