Brakes - ABS, ASC, and ASC + T Malfunctions

9217bmw01

Group 34
Brakes


Bulletin Number
34 01 92 (3490)


Woodcliff Lake, NJ
February 1992
Product Engineering


SUBJECT: ABS, ASC, and ASC + T Malfunctions Caused by Non-Approved Wheels and Tires

MODELS: All So Equipped


General
Information:
All BMWs equipped with slip-control systems (ABS, ASC, or ASC + T) utilize four wheel-speed sensors which monitor individual wheel rates of rotation with a high degree of accuracy. The system's control unit processes these individual inputs and computes a vehicle speed, and is thereby able to detect individual wheel speed variations from the computed speed.

If these inputs vary from each other by a certain amount, the control unit is unable to reliably perform its calculations ("plausibility" fault), and takes itself off-line as a safety precaution ("Fail-Safe").

If a complaint is received of any of these systems (ABS, ASC, or ASC +T) being inoperative, intermittently inoperative, or illuminating the warning lamp, verify that the vehicle is equipped with BMW-approved wheels and tires.

If it is not, DO NOT proceed with further diagnosis until the wheels and tires are replaced with original equipment (or BMW-approved) wheels and tires.

BMW of North America cannot test all combinations of aftermarket wheels and tires for compatibility with these systems. Therefore, ABS, ASC, and ASC + T cannot be expected to perform as designed unless BMW-approved wheels and tires are installed on the vehicle.


Please ensure that all service and sales personnel in your dealership are aware of the potential problems that can be caused by the installation of non-BMW-approved wheels and tires. Further, responsibility for correction of these problems must be borne by the installer of the non-BMW-approved items which caused the problem.