Today I had to get onto the brakes real hard, the ABS kicked in and I got the car stopped safley. When I stopped the BAS light and error message were on. This has never happened before. The battery is almost new and working fine, brake fluid ok,brake lights work everything looks good. I even dis-connected batt to try to reset, and it was still on immediately after starting. ANY ideas????????

 

Your stoplight switch is faulty and needs to be replaced.

 

It is common problems with MBZ. As mentioned in previous post it is either brake switch or dust in front brake caliper area, which can be washed away with high pressure water hose.

 

Hey sarmstrong, before you change your brake lamp switch you might wanna check your battery.

If tThe battery voltage was dropping down under 10 volts at times which is the threshold for the ESP/BAS system according to the Owners Manual.