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