The transfer case control module controls the adaptive xDrive transfer case wear in such a way that it is able to detect when an oil change is required. After changing worn transfer case oil, a BMW scan tool should be utilized to reset transfer case wear adaptations if the "54C6-VTG:There is an Oil wear fault code and such features may consist of an illuminated 4x4 inactive warning lamp. If drivetrain vibrations, juddering, or humming noises occur at speeds of 50 mph or more, particularly noticeable when coasting, along with grabbing, juddering, or chattering under hard acceleration in low gears, and vibrations while driving through turns at low speeds, it is first necessary to make sure that the tires at all four corners meet the following criteria: The same brand, size, and, wear/condition. Next, remove the harness connector at the VTG servomotor and road test the car; if the problem is gone change the transfer case oil and reset wear values in the VTG control module using a BMW factory scan tool. Further, if problems persist with new oil and a reset, it may be due to activation of clutch in the VTG transfer case, and will require analysis and possible service. There are cases some variants radiate the ABS, brake and 4x4 inactive warning lights or; the transfer case actuator will click after the shutting down the engine, this may be attributed to a faulty VTG servomotor caused by bad composite gear which was either worn or cracked and housed within the servomotor. BMW does not offer the gear for purchase individually, but there is an aftermarket gear which can be bought; further more when replacing the gear one has to dismantle the servomotor.
