Before Changing a Control Module

When all checks have been made as described in the action schedule under the appropriate diagnostic trouble code or by manual fault diagnosis, and no fault has been detected, it is natural to assume that the control module is faulty.
Considering that the control module is both a high quality and an expensive component, it is important to be as sure as possible of the diagnosis.
For this reason, run through the following points before definitely deciding that the control module is the cause of the fault.
1 Check one more time that all the checks in the appropriate fault diagnosis schedule have been followed through.
2 Study the appropriate wiring diagram and make sure that you understand it. If necessary, consult the appropriate parts of the technical description and the electrical function description.
3 Check all grounding points. If you have done this before, do it again.
4 Check the voltage supply to the control module.
5 Go through the points under "General fault diagnosis" Fault Diagnosis, General
6 If, despite this, the original fault remains, the Automatic Climate Control (ACC) control module must be changed.