Quote Originally Posted by JamesAustin View Post
As for the tail lights, BMW is into "adaptive brake lights" which show drivers following you how drastically you're slowing down. So far I've failed to confirm whether your car has them, but one of the ways BMW has implemented them is with extra bulbs that only light up during hard braking at speed. They don't light up at any other time, so unless someone follows you in a place where you can safely brake hard from speed, there's no way to test them. Try going back in there again and just looking for bulbs behind red lenses that don't seem to have any reason to be there. One other way BMW has implemented this is with brake lights that get brighter when you brake harder; maybe they use dual-filament bulbs and you have one with ONE blown filament?

I know all this because the very first issue I ever solved with my E91 was a burned-out adaptive brake light bulb. Neither wandering around my car with something blocking the brake pedal, nor watching my car's reflection in a glass-walled building as I pumped the brakes, ever revealed them.
Thanks, let's just hope it's the 3rd brake light. The car's at a friend's in Fairfax so I'll check again soon when I go back out.