Mercedes-Benz W210 BAS and ASR light and brake light switch
Why does the W210 BAS and ASR light come on?
A common cause is the brake light switch, whose failure can also switch off traction control. Fault code C0125 points to the switch. Other things to check: battery charge and charging, fuses, and the brake light bulb holders and bulbs. Brakes are safety-critical, so have a workshop check the end result.
Where is the W210 brake light switch and how is it replaced?
The switch is in the footwell at the top of the brake pedal, under the dashboard. Disconnect the connector, press the switch clip and turn the switch out. When installing, the switch plunger is pulled all the way out, and it sets itself correctly when the pedal is pressed. Have a workshop check the brakes after the replacement.
The light is on even though the brake light switch has been replaced, what then?
The fault may be in the BAS control unit connected to the brake booster, whose replacement switched the light off. A faulty control unit can also send wrong information to other units. Diagnosis and replacing the part are a job for a workshop, because it concerns the brake system.