Originally Posted by cc_bavarian
A good start is to go to BMW or a garage with a computer to find out exactly what error codes are being logged. The cost difference for an ABS pump vs ABS sensor is huge.
Agreed, it could be just a simple abs sensor throwing off an error. You could always replace the sensor first and clear the errors to see if the errors reappear. I have had the same issue on my E90 also, however it was just a sensor replacement.