[dimbo857]

Hello everyone,
I own a 2014 535xi and have intermittent issue with my radio/iDrive.
Every single morning when I start the car, radio and all the sounds work well. About 20 minutes later, all the sound/music shuts off and iDrive displays "No Warning Tones". Navigation and iDrive remains functional. Sometimes before completely cutting out, radio works on and off every couple of seconds before completely going out (see youtube link to below) . When it completely cuts off -the clock/time in iDrive freezes. I have a Harman Kardon HiFi audio system and NBT iDrive,
ISTA-D shows 3 faults
- No connection with KOMBI (dashboard)
- No connection with Amplifier
- MOST ring break
If I lock the car for about 20-30 minutes and return - all the sound comes back and works for about 10-15 minutes before shutting off again. Tried installing used amplifier from a similar vehicle and there was no change in behavior - it did the same exact thing. I tried using fiber optic loop in both kombi and amplifier and the issue still seems to occur. Checked the battery and it's good. Any ideas? All help is greatly appreciated!

https://youtu.be/mIubnhQF940

[Surly73]

My first instinct would be to take some things apart and re-seat connections. The error messages you report seem bang on - the MOST ring (a fiber optic network mostly for "entertainment" signalling) is being interrupted. Temperature cycling may be wiggling a connector apart or similar.

Worse would be if there's an internal fault in one of these components, and when it gets hot a fiber transceiver just stops working.

[dimbo857]

Thanks for your response. Do you know if there are any other modules on MOST bus aside from instrument cluster, head unit and amplifier?

[Surly73]

I don't have one, but they might be out there.

A quick google gave me an F10 M5 technical document with a chapter on MOST.

https://www.google.com/url?sa=t&rct=...IlEWygsXCGBsjr

[dimbo857]

The whole NBT head unit had to be replaced and coded. Bought a used one off ebay for $200. All fixed.