Diagnostic Functions

Diagnostic functions

General
All diagnostic communication regarding the gas discharge lamp module (GDL) is handled via the central electronic module (CEM).

Diagnostic trouble codes (DTCs)
If the central electronic module (CEM) detects a fault in the headlight system, it stores a diagnostic trouble code.
A fault detected during the last driving cycle is defined as permanent. Other faults that are detected are defined as intermittent.

Replacing the gas discharge lamp module (GDL)
If the gas discharge lamp module (GDL) (master) or any of the gas discharge lamp position sensors are replaced, the position sensors must be calibrated.
After replacement with a new gas discharge lamp module (GDL) (master), diagnostic trouble codes CEM-8A20 and CEM-8A21 are generated. These codes are deleted automatically after position sensor calibration.
Calibrate as per the tab DIAGNOSTICS/VEHICLE COMMUNICATION/Central electronic module (CEM).
Calibration must always be performed with the vehicle unlocked and stationary on a level surface.