On the E90 almost all of the brake/tail lights are the same kind of bulb. There is one exception, and that is one bulb on the inner tail light that is built into the trunk lid. It’s a small, hard to find bulb called an H21W. Mine haven’t been working, which is of course causing the triangle error message on the dash. I got some replacements and installed them and they’re still not working. According to the owners manual these should be brake lights. Can someone please shed some light (sorry for the cheesy pun!) on what the problem might be? I am including some photos for reference.
Bump... nobody has any thoughts on the lights?
I read somewhere that "additional brake lights (light up) whith harder/sudden braking (something to this effect); now, I cannot find it again/ nor do I have any clue as to "how" the sucker knows what "harder braking" means and how these operate; my initial reaction would be that the brake light switch at the pedal has two stages (as to pedal travel, or possibly related to the ABS sensors). See if you can find the wiring diagram for those and perhaps that could help you trace the functionality.
Perplexing issue, perhaps someone can chime in with better answers.
Just hoping that this could be a clue for you.
Those are the rear fog lights on European cars, and the adaptive brake lights on American cars. They only turn on during extreme panic stops (ie the ABS unit is intervening).
ASE and BMW Master Certified Technician
So, if I am understanding correctly, I should not expect to be able to see those small, inner brake lights working under any circumstances while the car is parked in my driveway? I tried having my wife smash the brake pedal real hard and fast, and that didn't make them come on.
I'll be honest, I don't care as much about when, how, or even if those little lights come on. I just want the "light out" error to go away from my dash. I'm tired of the car dinging and putting up triangles, etc. If that isn't the problem, what else could it be? I cannot find any other lights that don't work on the car.
Thanks for your help!
Assuming that the lightbulbs work and you checked them by themselves, I wonder if a reset is needed/required...
i.e. go out on a "quiet/safe" country road, jump on the brakes at 35mph and see if the "computer" now detects the bulb resistance and the error clears afterwards...
A reset is not required. The Footwell module continuously pulses all the bulbs and will turn off the warning either immediately, or after a key cycle.
You will not be able to activate those lights while sitting still in your driveway. The proper way is to do a diagnostic test with the proper BMW software. It will tell you what bulb is out, as well as have the ability to activate and test any and all light bulbs on the vehicle.
ASE and BMW Master Certified Technician
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