Intermittent fault-tracing: Notes

The reason the car is in the workshop is because the customer has experienced abnormalities with the car. The symptoms experienced by the customer does not always coincide with a permanent fault. The fault might not occur when the customer arrives at the workshop but occurs on a single occasion.

In order to deduce the fault type is important to check the symptoms reported by the customer:

• How does the car behave? Is the car difficult to start, are the gears hard to shift, does the tachometer flicker etc.
• What are the circumstances when the fault occurs? under heavy load, is it dependant on the weather, outside temperature, on uneven roads, when making sharp turns, only when the engine is cold, under hard braking etc.

It is important to interview the customer about the surrounding circumstances in the event of a fault.

It may be an advantage to simulate the driving conditions for when the symptom occurs and carry out an analysis and deduce the fault. By deducing the fault, the symptom can be remedied so that the fault does not recur.

When a diagnostic trouble code (DTC) has been stored the freeze frames are also stored. These can be used to recreate the driving conditions for the diagnostic trouble code (DTC).

Tools:

• Reading off freeze frames, read off the freeze frame data for the relevant diagnostic trouble code (DTC)
• Status identifier, read off the status of the selected diagnostic trouble code (DTC)
• The counter indicates, amongst other things, how many fault free cycles have been carried out since the diagnostic trouble code (DTC) was stored.