We've got a similar issue with our '08 X3. Dash light triad and rumbling at highway speeds.

Yesterday we replaced the xDrive servomotor actuator on the transfer case, but it seemed to make no difference.

Is there some way to lock the transfer case electrically so I can see if anything's mechanically disconnected (e.g., broken transfer case chain)?

Here's what INPA says in the transmission section (after translation):

E R R O R M E M O R Y --------------------------------------- Date: 16.05.2021 11:52:45 ECU: VGSG83 JobStatus: OKAY Variant: VGSG83 ------------------------------- ------------------------------ RESULT: 2 error in error memory! ------------------------------------------ ------------------- 54C8 54C8 Classifying resistor on the servomotor Error counter: 2 Logistic counter: 40 1. Environment set Mileage 287 160 km input voltage KL30 13.63 volts KL15 status CAN CAN signal OK - KL15 on 0-n KL15 internal KL15. on 0-n motor speed CAN signal OK - ICE on 0-n reset source NO RESET 0-n MKSOLL 0.00 Nm MSperrIstPosLim 0.00 Nm LockError 0.00 1 LockMainState 16.00 1 SGTemp 28.00 degrees C iSM 0.00 Ampere 2. Environment set Mileage 287 160 km input voltage KL30 12.38 volts KL15 status CAN CAN signal OK - KL15 on 0-n KL15 internal KL15. on 0-n motor speed CAN signal OK - ICE off 0-n reset source NO RESET 0-n MKSOLL 0.00 Nm MSperrIstPosLim 0.00 Nm LockError 0.00 1 LockMainState 48.00 1 SGTemp 30.00 degrees C iSM 0.00 Ampere Implausible signal or value Test conditions met. Error currently present and already saved. Error would not cause a warning lamp to light up Error code: 54 C8 68 02 28 8C 37 6D ED 00 00 00 10 0E 00 8C 37 63 E5 00 00 00 30 0F 00 ---------------------- --------------------------------------- 55C4 55C4 CAN_MESSAGE_DSC1 Error counter: 1 Logistic counter: 40 Mileage 287 160 km input voltage KL30 13.63 volts KL15 status CAN CAN signal OK - KL15 on 0-n KL15 internal KL15. on 0-n engine speed CAN signal OK - ICE on 0-n Reset source NO RESET 0-n MKSOLL 0.00 Nm MSperrIstPosLim 0.00 Nm deltaPhiSperreCal -51.00 Grad LockError 0.00 1 LockMainState 16.00 1 DSC1_Fehlersignale DSC1_MK_SOLL 0-n Implausible signal or value Test conditions met. Error does not exist at the moment, but has already been saved. Error would not cause a warning lamp to light up Error code: 55 C4 28 01 28 8C 37 6D ED 00 00 33 00 10 01 00 00 00 00 00 00 00 00 00 00 00 ====================== ========================================

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2008 X3 (E83-LCI) 3.0si M-Sport
2004 X5 (E53-LCI) 4.4i M-Sport
1994 318i (E30-LCI) race car - sold