Just got the car back from the shop where they had to fix the oxy sensor, and also ended up replacing the eng wiring harness due to deterorating wire coatings...

I've check the fuse (#5) and it's fine...dug in and pulled the Brake light switch - it has power going to it for both sets of wires, and a continuity check seems to indicate that it is working...

Wiring diagram seems to indicate that everything goes through the "Exterior Lamp failure Monitoring Unit" - but don't know how to check if that somehow has failed....

All other lights work - it's just the brake lights.

Any ideas?

UPDATE: **********************

Upon further examination there are other lights that don't seem to work - Including the brafke lights, the license plate lights, and the side marker lights also don't work. Grounds were all checked and haven't been touched. Rear lights ground to wheelwheels in rear of can - either side..



Thanks for any help

The "Lamp Failure Monitoring Unit" would affect all of the lights in the circuit...headlights, taillights, parking lights, license plate light, etc. If that unit was bad, either nothing would work, or upon failure would shunt the network to allow uninterrupted operation of the lighting system (which I believe is the MB way of designing a circuit).

Since you said the other lights work fine, I would have to rule that unit out.

I'm more inclined to believe that a ground wire may have been knocked loose during the wiring harness replacement.

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2009 ML350 (106K) - Family vehicle
2001 CLK430 Cabriolet (80K) - Wife's car
2005 BMW 645CI (138K) - My daily driver
2016 Mustang (32K) - Daughter's car