Checking the Basics

When all checks have been carried out in accordance with the diagnostic procedure described under each diagnostic trouble code and no fault has been found, it is natural to assume that the control module/instrument is at fault.

In view of the fact that the control module/instrument is an extremely expensive high-quality component, it is important to ensure as far as possible that the diagnosis is correct.

Go through the following points very carefully before definitely deciding that the control module instrument is the cause of the fault.





1 Check once again that every single point in the diagnostic procedure or checking schedule for the relevant diagnostic trouble code has been carried out.

2 Study the wiring diagram of the circuit in question and make sure you understand how it works.

3 Check all grounding points. If you have already done so, do it once again.

4 Check the power supply and the fuses for the control module/instrument.

5 Check that there are no slide-outs in the control module connector.

6 Go through the points in "Points to remember when diagnosing faults" and "fault diagnosis hints" for the system one more time. Description of On-Board Diagnostic System

7 If the fault persists in spite of this, then the control module/instrument will have to be changed.