My 07 335i coupe had the bulb warning light come on with the CC-ID 134 code (right rear brake). All the bulbs tested good and I moved them around but still had the warning light with the same code.
I replaced all of the 921 bulbs in the right tail light assembly and the warning light went out. For good measure I replaced all of the 921 lamps in the left side light assembly as well.
Looking at the bulbs some were blackened but still working. Early warning system I guess.