Finally, a subject I can reply to that I have some knowledge about
I had this happen to to me and it drove me crazy! I had it to 3 dealers. They each had different suggestions on how to fix the problem, but nothing worked. Replaced ALL the bulbs, replaced the middle brake light bulb in the back windshield, double checked the connections on all the wires. Nothing worked.
Until I had the car in for a normal service interval and i asked them (again) to see if there was anything they could do to fix the "Brake Light" issue. I picked up the car, no more Check Brake light fault ! I asked the mechanic what he did to fix it. He had to replace the ballast (I think that's what its called) that holds all of the light bulbs that connects to the inside of the tail lamp assembly. He said even if everything works OK as far as lights working, the computer on board can detect if the ballast is going bad, even before it fails.
I sure hope this helps, it took me a solid year to get rid of the fault and the ding every time I turned off the car.
Now if someone brings up the other issue i struggled with regarding sitting in the drivers seat and tripping a fuse that controls the seat and steering wheel controls, I'll really feel like I'm helping my fellow M5'ers.
let me know if this helps :M5launch::M5launch::M5launch::M5launch::M5launch: