Jose Garcia, one of ATSG’s Technical Field Advisors was called out by one of the local shops here in Miami, to help sort out a 2008 BMW 328Xi AWD (E90) problem.
Originally, the vehicle came into the shop with the ABS, Traction Control and Brake light lit up in the instrument cluster. It was like a Christmas tree with beautiful red and amber twinkling colored lights.
The center information panel had messages of worn brake pads and a bad wheel speed signal. The scan tool had also pulled codes related to these messages along with code 5F4A - Transfer case malfunction.
The shop went ahead and replaced brake pads, pad wear sensors, and front wheel speed sensors. This eliminated all the related codes except for the 5F4A code and the trio of lights remained on.
Jose noticed that as soon as the vehicle was started, the triad of lights came up immediately. But he also heard a grinding noise coming from underneath the vehicle.
The vehicle was lifted up on the hoist so Jose could inspect where the noise was coming from. Once it was up in the air it was obvious he wouldn’t be able to see a thing. The exhaust and shielding blocked everything. So after removing the exhaust system and shielding, he was able to determine that the noise was originating from the Transfer Case motor. He quickly removed this little motor from the Transfer case and held the drive gear with his hand. When he had the vehicle started, the motor started to cycle and he could hold the gear stationary. Simultaneously a ratcheting/grinding type noise was heard. Confirming a bad motor, he took it apart and found the internal worm gears were stripped out as figures 1 through 4 reveal. $300.00 later for a new motor and a Transfer Case fluid change and the problem was resolved. Not only was this problem resolved, the triad of lights also turned off!
Apparently this vehicle uses an xDrive system in conjunction with the ATC 300 (Active Torque Control) transfer case. This system works in combination with the Dynamic Stability Control Unit for all wheel drive control. So if the transfer case becomes unable to drive the front wheels, the brake system warning lights come on to inform the driver of a problem. So in reality, this vehicle had bad brakes, bake brake wear sensors, bad wheel speed sensor and a bad Transfer Case Motor; a quadruple problem revealed by a triad of lights. This also seems to suggest that just a transfer case control motor problem could also turn on all three lights.
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