BMW Z3 ABS and ASC light on
Z3: why do the ABS and ASC lights come on while driving?
The usual cause is the circuit board of the ABS unit's control module: vibration breaks the solder joints near the connector. The fault can come and go with temperature. Re-soldering has fixed the lights when the other parts were fine.
Z3: why does the ASC light flash and power cut out under hard acceleration?
If the tyres are smaller than the original size, the wheels turn at different speeds and ASC reads that as wheelspin. For example, 205/55-16 tyres instead of 225/60-16 caused this above 4000 rpm. Tyres of the original size removed the flashing.
Z3: where is the ABS control module and what has to be done for a new one?
The module is on the engine-side flank of the ABS unit near the brake booster, and it comes off with a few screws and one large connector. The old one can be repaired. A new module must be coded to the car, and the front wheel sensor calibration must be set. Coding takes about 10 minutes.