[Knuppel]

My wife got warnings on the dash concerning just about every bulb in the car. Visually checked, only the left inner tail light was out (the one in the tailgate). I took out the brackets on both sides, and found the tail light bulb sockets to be full of oxidation. Moreover they both showed signs overheating. The metal on the underside of the bulb was completely gone. The plastic around it also. I replaced the housings with OEM blackline some time ago; both my old and the used ones i got had this issue, so i'm guessing this is a well known problem.

I've succesfully cleared most of the oxidation from the sockets and put everything back together. All the other bulb notifications went away upon flipping the light switches, but the left tail light stayed; i've confirmed visually it's still not working. I've flipped bulbs with ones i known working ones. Also, i had to run a reverse camera cable to the tailgate, whilst i was at it i checked the wires, they all looked fine.

Is there something else i can try? Can i swap left and right bulb brackets or are they differently wired? Do i need to clear error codes?

[Serf27]

The errors self clear when a bulb is good.
You can swap the bulb housings from one side to another to see if that’s the issue.
The FRM may have also stopped sending power to that bulb and now needs an “FRM counter reset”.

The e91 is also getting a bit famous for ripped wires at the boot that connects the hatch to the body of the car.

Swap the housings first and see what happens.