X5 becomes a Christmas tree

[sv1cec]

This morning I started from our house with a car, and I returned with a Christmas tree.

To explain: As I was waiting at a traffic light this afternoon, I hear a beep and I see the following lights switched on, in the dashboard: the 4x4 light, the ABS light and the brakes light (the one with the ! mark). A little later on, the left rear tail light warning light came also on.

I visited the local BMW dealer, who connected the car to his computers and did some "alignment". The lights went off, but when the mechanic took it for a drive, the lights came back on and he said that I need to have the 4x4 motor replaced (I think the proper name is Transfer Case motor). Total cost is about 800€ (about $1,100 for you Americans).

Now, it's not that I do not trust the dealer, but since I have the INPA software and the programming cable, which module shall I check to see if indeed the motor needs to be changed? And what would the error be?