Has the re-call on the tail lights been done? If so, if it was done incorrectly, a voltage spike could have gone to the General Module. The General Module runs things like the stereo, dash lights, etc. I had the tail light re-call preformed at my local BMW Dealership, and had electrical problems right after it was done. WHen the re-call Ground wires were hooked up, the Tech shot positive voltage up thru the system and it shorted out about half of the General Module (all because he was too lazy on a Friday afternoon to remove the battery ground before doing the re-call). Some of the features that didn't work after the re-call; interior trunk lights, footwell entry lights, all 4 map reading lights, door open chime (these all worked correctly prior to re-call being performed). Diagnostics indicated a partly shorted out General Module. The General Module was a $400 part, less than an hour to install, but then the car and all keys had to be re-programmed, thus turning into a $900 bill. I paid the bill but thru several talks with BMWNA, I finally got to speak with the field service tech/advisor and he responded that I had a very valid point about disconnecting the battery ground prior to doing the re-call and we agreed on settling by dividing the cost of parts and labor in half.
Your BMW Dealer should be able to trace out the problem with computer diagnostics in an hours time (about $90), tell you if its indeed a K Buss or General Module problem. If you bought the car from a used car dealer and it had a warranty on it, have them pay the BMW Dealer for the diagnostic time as they should have had the problem corrected before you bought the car (unless you bought it AS IS with no warranty). If you bought the car from a BMW Dealer, it should have be fixed before you picked it up if they truly value your business and hope to have you return for routine services.
On a side note, did the stereo shop check ALL the fuses? Several electrical systems in these cars use 2 fuses within the fuse black for protection, shared fuses with other systems. In the fuse block door, there should be a card that lists all the fuses and what system they are related to besides the amperage of each fuse. Easy for you to check and see if you have any other bad fuses, use the audible sounder on a DMM to check for an open/burnt fuse, black test lead on one side of the fuse and the red lead on the other side of the fuse, sound, the fuse is good, no sound the fuse is open.
Last edited by tomoyer; 10-07-2012 at 06:28 AM.
Reason: wrong word