Although it is possible for the home mechanic to remove the hydraulic unit, the unit's self-diagnosis system must be interrogated by dedicated test equipment before and after removal, and the unit must be bled by BMW service test equipment. Consequently, removal and installation of the hydraulic unit should be entrusted to a BMW dealer or suitably-equipped specialist. For similar reasons, the removal and installation of the accumulator should also be handled by a BMW dealer or qualified repair shop. To remove the ABS/ASC+T ECU, the hydraulic unit must first be removed as the ECU is attached to the side of the hydraulic unit, making it advisable to have a dealer or qualified repair shop perform this task. For the front wheel sensor, chock the rear wheels, apply the parking brake, jack up the front of the vehicle, and support it on jackstands. Remove the appropriate front wheel, trace the wiring back from the sensor to the connector in a protective plastic box, unclip the lid, and disconnect the wiring connector from the main harness. Loosen and remove the bolt securing the sensor to the steering knuckle, then remove the sensor and lead assembly from the vehicle. Note that on some models, the front wheel sensors are handed and marked L and R, with the right-hand sensor having two green markings. Before installation, apply a thin coat of multi-purpose grease to the sensor tip, ensure the sensor and steering knuckle sealing faces are clean, and fit the sensor to the knuckle, making sure it is installed on the correct side of the vehicle. Install the retaining bolt and tighten it to the specified torque, ensuring the sensor wiring is correctly routed and retained by all necessary clips, then reconnect it to its wiring connector and securely clip the lid in position. After installing the wheel, lower the vehicle to the ground and tighten the wheel bolts to the specified torque. For the rear wheel sensor, chock the front wheels, jack up the rear of the vehicle, and support it on jackstands before removing the appropriate wheel and the sensor. The front reluctor rings are fixed onto the rear of the wheel hubs; examine them for damage such as chipped or missing teeth, and if replacement is necessary, the complete hub assembly must be dismantled and the bearings replaced. The rear reluctor rings are pressed onto the driveaxle outer joints; examine these rings for signs of damage and replace as necessary, with the driveaxle assembly needing to be replaced if replacement is required.
Posted by BMWPartsDeal Specialist 
