2000 C230k - Bas/esp
 

BAS/ESP light goes on and off. Sometimes its on when I start the car, sometimes it goes on when I am driving, sometimes it is off for several days, sometimes it is on for several days. I changed the brake light switch but the problem continues. Sometimes it goes on under braking but just as often it will go while driving along. My independent can't read the code and the dealer is far away. Can any tools access this system? Any ideas besides the brake light switch?

Diaphragm travel sensor on the brake booster would be my personal guess #2.
Gilly

Thanks. Is there a way to check with a multimeter? I am not sure if it is the BAS system or the ESP system. The traction control, ABS and cruise all seem to work when the light is on. Would that eliminate the possibility of a wheel sensor?

I think you need the reader to read the travel sensor output, so generally better off in the long run in just going at getting the trouble code read.
Gilly