BMW E87 DSC and traction control light on or flashing
Why does the E87 DSC or traction control light come on and power is lost?
The most common cause is a rusted and swollen ABS ring, a toothed ring on the driveshaft hub. It rubs against the wheel speed sensor, and the system receives incorrect rotation data. The car may jerk, and power is lost especially when cornering or on the motorway.
How is the fault repaired?
Replace the ring and check the sensor, and replace the sensor too if it shows signs of wear. Replacing only the sensor is not always enough. A shim under the sensor helps only temporarily. The permanent repair is new rings, and the ring is sometimes part of the driveshaft.
Is it worth using cheap sensor and ring parts?
Not necessarily. Cheap sensor and ring kits do not always work, so use original or good-quality parts. A workshop can find the faulty wheel by reading the wheel speeds with a diagnostic tool: the speed of one wheel fluctuates compared with the others.