Checking the Stop Lamp

Checking the stop lamp

Checking the wiring and the relay
If the brake light does not light up, check the cable between the central electronic module (CEM) terminal #6B and the rear electronic module (REM) terminal #4A. Check for an open-circuit. Check for a short-circuit to supply voltage.
If the brake light is constantly lit, check the cable between the central electronic module (CEM) terminal #6B and the rear electronic module (REM) terminal #4A. Check for a short-circuit to ground.

Hint: When the brake pedal is depressed, there should be 0 V in the connections, otherwise 12 V in the connections.

Check the relay (2/79).

Hint: There should be a 12 V supply to the relay switch to terminal #5 and in the supply to coil #2. When the brake pedal is depressed, there should be 12 V in the relay switch #3.

Check the cable between terminal #5 and fuse 3 in the cargo compartment fusebox (11D/3).
Check that fuse is intact.
Check the cable between relay #3 (2/79) and shunt brake light #3 (20/31).
Check shunt (20/31).

Hint: The voltage must be 12 V at the shunt terminals, i.e. at terminals #3 and #2 when the brake light is active.

Check the cable between shunt brake light #2 (20/31) and brake light #2B (10/54 for left brake light and 10/48 for right brake light).
Check the ground supply between the brake light terminal #1B and the ground terminal.
If no fault was found, replace the brake light.

Other information:
- For information about signals, see Signal specification Signal Specification
- To replace the brake light, see Bulb tail lamp/stop lamp/back-up lamp/fog lamp, replacing Service and Repair
- Checking wiring and terminals Checking Wiring And Terminals.









Is the function OK?

Yes - FAULT FOUND

No - No Fault Found

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