Mercedes-Benz W210 ABS, ESP and BAS warning lights on
W210 ABS, ESP and BAS lights on - what can cause it?
Common causes are a weak battery or voltage drop, a faulty brake light switch, the wheel speed sensor or its tone ring, the steering angle sensor, and the pre-charge pump of the ABS pump. Read the fault codes with a diagnostic tool. Brakes are safety-critical, so have a specialist check the brakes after the repair.
Why do the lights come on after the battery has been changed or disconnected?
Disconnecting the battery or low voltage confuses the system, and the centre position of the steering angle sensor has to be reset. Start the engine and turn the steering wheel from lock to lock and back. Sometimes the lights also go out after a few brake applications. If they come on again, the fault is real and must be repaired.
Can the brake light switch or a wheel speed sensor cause the lights?
Yes. A faulty dual-function brake light switch turns on the ABS, ESP and BAS lights even if the brake lights work. It is cheap and easy to replace. If the code points to a wheel speed sensor but replacing the sensor does not help, the tone ring may be cracked even if it looks intact.
Can a crooked steering wheel turn on the ESP light?
Yes. If the steering wheel is off-centre when driving straight, for example after work on a control arm or tie rod, the ESP may interpret it as a fault. Have the wheel alignment checked. Even a small tyre pressure difference can also trigger the light, so check the pressures.