You need BMW Standard Tools suite and a Bimmergeeks
Cable plus a laptop. (Go to the coding sub forum for this)
Then you have to use it to read how the modules are coded.
If you have a car made after 3/07 you may need the more expensive
Icom Cable to program Most Bus modules.
You can try to default code the Head Unit with the CAR VO if it still
had Logic 7 (option 677 and or 688 in the VO)
This starts our by learning to read an program the modules in
NCSexpert. However a SOS error does genrally result from
a broken Most Loop.
Most test point
http://www.e90post.com/forums/showthread.php?t=347222
You should see a Red Light coming out of one side of the Head unit on the
Most Bus cable.