[geo.k23]

Originally Posted by Steven211

Hi up until this year I was a BMW technician, and those faults are voltage related, they will always pop up with low voltage or when the battery has been disconnected. The 4x4 system relearns itself. In terms with the clunking, transfer boxes are known to fail on them and can cause clunking on the rear, they are programmed to the vehicle too so 2nd hand units cannot be fitted. I've known rear diffs go before but very very rare. I'd book it into an independent BMW specialist who has the latest ISTA-D software or BMW themselves as there will be codes stored, the BMW diagnostic software will say what to replace.

Though a little tip, if you have access to a ramp or have a good mechanic, get them to unplug the transfer box connector and see if the fault goes away, if it does then the transfer box is screwed. That is an official BMW test procedure that technical used to tell us to do.

thanks for all the input you mention disconnecting the transfer box is it advisable to leave it disconnected it was a great car up until i put it off the road for a couple of months thanks