2004 'Vert Driver's Brake Light Not Working, Tail Light Works

[OneSwellFoop]

I've got a 2004 M3 convertible in Laguna Seca Blue. It's got the stock LED tail lights and, intermittently, the driver's side brake light doesn't work. The tail light overall has sometimes not worked but now, consistently, the tail light works, just not the brake light.

Is there a controller unit in the light that may be the issue? Is this a known issue that I've simply not heard of in my years of ownership and research? Is it likely something as simple as having a bad ground somewhere?

[oceansize]

Ahhhhh, I can see the problem, it's LSB

[OneSwellFoop]

Ahhhhh, I can see the problem, it's LSB

Even worse, I got it with 95k on it for $14,300 in late 2018!

[drivem3]

Get a new taillight, that will fix the issue. Had the same thing happen on my '04 M3 on the left taillight. Went down the rabbit hole on research and also thought it was grounding/electrical related but it was simply just worn LED bulbs.

Bought a new pair online and completely resolved my issue.

[OneSwellFoop]

Get a new taillight, that will fix the issue. Had the same thing happen on my '04 M3 on the left taillight. Went down the rabbit hole on research and also thought it was grounding/electrical related but it was simply just worn LED bulbs.

Bought a new pair online and completely resolved my issue.

Thanks! I was hoping to avoid the expense but, really, can we ever avoid the expense with M cars?

[Shonky]

Thanks! I was hoping to avoid the expense but, really, can we ever avoid the expense with M cars?

There's a few DIYs around on replacing individual LEDs. Unlikely to be your problem though. Also there was a TSB on the grounding going high resistance although I think that may have been the non LED units as they would draw more current. Still worth a look.

The units are pretty well sealed if it's internal but you don't have much to lose if you're technical enough to have a look. Worst case you're buying a new one either way.