Mercedes S Klasse Brake Light Issue

Sounds familiar! I had a similar issue with my S Klasse. If the bulb is OK, it's almost certainly the brake switch. Cheap part, but fiddly to get to. I thought I had fixed it, but the error came back after a week.

Thanks for the quick reply! When you say fiddly, what exactly do you mean? Is it just awkward to reach, or are there specific things to watch out for? And when the error came back after a week, what did you do?

Yeah, awkward to reach up under the dash by the brake pedal. I messed with it, probably didn't seat it right. I ended up taking it to the workshop. They said it was the switch, replaced it, and all good since.

You were spot on! I decided to try my luck and took it to a local mechanic. They confirmed it was indeed a faulty brake switch, likely caused by accidentally kicking it while driving. The switch was reset, and the error is now gone. The tail light is working perfectly again. The repair cost was 0€, thankfully. Thanks again for pointing me in the right direction; your help was invaluable!