Speakers not working, phone and music

[neliconcept]

So today, randomly the speakers decided not to emit sound at all. Could this be a fuse issue? I've been having issues with my driver side window switches as well but that seems to be wiring as they do work here and there and then they don't. Wondering if this could be an issue with my FRM module as well. So ready to trade this in as my A/C also does not work.. Freaking nightmare of shit happening all at the same time.

07 4.8 if anyone is wondering.

[Aquamania]

First check all the fuses. Then if they are good, it is time to find a good indy mechanic.

[neliconcept]

Speakers started to work again. Now a bit confused.

[BorisKV]

I am not sure if this applicable in your case, but I have 08 4.8 and I was having a very similar issue.

Initially it was a pretty rare occurrence and sound would disappear (both when playing radio/media and with parking sensors on) for a while and then reappear again. Then eventually SOS message came up. I did diagnosis with ISTA/D, there were error codes related to MOST and it appeared that one of the modules was breaking the MOST ring. MOST ring is essentially optical cable for media network where commands and media data flow through, the packets are picked up by targeted device and then those commands are executed. Any breakages in that ring will result in media system connected components not working. There is a special test procedure in ISTA/D which allows one to narrow down the module that wasn't working to couple modules around the breakage (MOST Ring Break test).

So I've purchased the loop from BMW dealership and started disconnecting optical connectors from modules in the vicinity of breakage and replacing them with said loop. Turned out that my SiriusXM module was dying, not completely dead but dying and replacing that module with the loop solved intermittent sound issues. So after disassembling the module, trying to troubleshoot electrical components, I decided it was much simpler just to get a replacement unit from another car. Since then, no issues.

Maybe your case is different but I would start with reading any stored codes to see if there are any reports related to MOST ring and trying to figure out which module is at fault.

Here are couple good links to read more on this subject:
How to Troubleshoot MOST bus or how to find the faulty MOST unit ON ANY BMW, AUDI, PORSCHE, VW, MERCEDES BENZ and other cars with OPTICAL FIBRE OPTIC MOST network | BMW LOGIC7
http://www.bmwmotorsports.org/BMW_docs/mostbus.pdf
Resource - MOST bus fault patterns - Bimmerfest - BMW Forums

Good luck, as this issue is a PIA to diagnose.