I screwed up a simple explaination again I think with too much info......?........let's try this.
CCP = check control panel in headliner
VDO = amber triangle in cluster
LED = brake bulb warning in CCP
CCB = the test/reset button on the CCP
1] when you start the car AND do NOTHING else, the LED & VDO will be on.
2] step on the brake and both SHOULD go out, if the bulbs/circuits are good.
3] if they stay on after depressing the brake pedal,
a] there's one or more bulbs out
b] defective HMSL circuit board [sorry, HMSL=3rd brake lamp]
c] bad brake lamp switch
4] if the VDO & LED come on while driving [you've hit the brakes] it's usually due to [a] but can also be corrosion or looseness in the lamp assemblies. Pressing the CCB will turn off the VDO until the next braking event with a lamp problem, [a] or [b].
5] this system can't tell you if the brake lamp switch goes bad after you start the car.....it will have no way of knowing you've touched the brakes.......later model BMW's do [a double contact switch].
6] if all the bulbs are new and CORRECT, and the contacts are CLEAN and working BRIGHTLY [ DON'T use brake lamp bulbs for taillamps!! the lamps will melt!] the problem is the HMSL circuit board.
HOPE THIS IS CLEAR NOW.........................jeff b........................