Trailer Hitch

Fault code 0526

Brake light switch

Diagnostic conditions
- Ignition on
- Trailer hitch control module, internal function test

Possible causes of fault
- Communication via CAN comfort disrupted
- Problem with brake light signal from brake light switch
- Brake light relay faulty (relay carrier at left of dashboard)
- Signal lead from brake light switch faulty (open circuit, short circuit to B+ or ground)
- Fuse F38 and F26 (fuse carrier on the left)
- Brake light switch faulty
- Trailer hitch control module faulty

Affected pins
Trailer hitch control module, plug B:
- Pin 3

Diagnosis/troubleshooting

NOTE: The trailer hitch control module receives the brake light signal in two ways: as an analog signal via the signal wire (plug B, pin 3) and also via the CAN comfort bus from the PSM. A cyclical check and comparison of both sets of information takes place in the trailer hitch control module (redundancy). If different comparison values are detected, a fault is stored in the fault memory.