01 E320 - Potential SAM failure?
From what you have said - for me it reads as one rear brake light out - from memory (and I could be foggy) - MB rear brake light bulbs have a "different" pin placement - like 12PM/4:30PM pins I believe - where auto parts store/general bulbs same size have a 12PM. When you jam in a generic 12/6 pin - some can get it to work - but ultimately it wacks out the socket.
Suggest you consider replacing that rear brake light on the bad side 1st - replace with correct bulb "both" sides - and start from there.
If it was me - while doing that - I would also choose a pre-emptive brake light switch replacement - genuine MB part only - under $20 - but that's me.
From there - I think it will be most likely a circuit/rear problem - you would be the 1st "blown SAM" I have seen.
Yes - W210's have wacked out rear brake lights...



