[Umfall]

Hi all!

I have a weird problem with my Harman Kardon audio.

TLDR: Sound works for a short time after the car was left unused for more than one night. ISTA: MOST ring break. No light in the optic fibre but there is a red light in amplifier itself. "diagnostics" guy states that the problem is in amplifier. Electronics service states, that amplifier is good.

Short backstory: I've imported my Bimmer from USA- lightly crashed in front (airbags didn't explode). While putting car together audio worked like a charm. After the repair I recoded my car using BimmerCode. Also that day I cleaned evap with a spray cleaner. (I pulled out the radio and there was no water traces) The day after coding all the issues with sound started. Sound would randomly disappear with the prompt "No warning tones". It would turn on and off every couple of seconds. Sometimes audio worked the whole day, sometimes not at all. I didn't have time to deal with it because it's my daily.

Current state: Most of the times sound works (for couple of minutes, then it starts to turn on and off until no sound at all) after the car was parked for longer than overnight. Sometimes it works randomly during the ride. Moreover there is no communication between modules as there is no info about fuel consumption on the screen (I have it on the cluster) and no sat nav info on the head up.

Troubleshooting: I've read error codes with ISTA, screenshot attached. As it diagnosed MOST ring break and no communication with the amplifier I thought that amp is the issue. I left the car at the electronic guy and he also diagnosed, that it is 100% amplifier fault. He thought that it might be cluster, but after replacing it problem was the same. After that I've sent the amplifier to another company that repairs them. They tested it and said, that my amplifier is 100% good. As a side note: before plugging the amp back to the car there was no light in the optic cable. After plugging it the sound was working and there was light in the cable. After couple of minutes sound died and no light in the cable. Plugging out and in does not change anything- for a short time after plugging in there is visible red light in the amplifier.

Of course I've checked fuses and connectors in the first place.

So after spending couple of hundreds euro I still don't have sound.

Do you have any ideas what should I check? Is it possible, that there is some simple issue with coding or power shortage? I'm really hopeless

EDIT: After finding yet another electrician and simply swapping NBT problem was solved. I fitted used NBT, got it coded and everything works like a charm. Thank you all for the tips and support

[NealfromNZ]

On the fibre cable side of things I’d be temped to try and eliminate that as a potential source. First thing would be to check behind the idrive and make sure there aren’t any kinks or overly tight radius that cause the light to refract which will cause errors.

If that’s looking ok I’d buy an aftermarket idrive to Hk amp section of fibre of 5 meters and run it from idrive to amp run loosely through interior of car . Run your idrive for 20 minutes or so with it sitting on the console and see if you get warning tone / most ring error. If this runs without issue then you’ll need to run the new cable through the left side interior path. Same approach could be used for the Most cluster section.

Have a look in aliexpress and search
bmw harman kardon most and look for cables with the right end connnectors for amp end and console end.

Note , the amp fibre cable is sold in 4 or 5 meter lengths. 4 meters is too short for factory cable path.

[sam330e]

Hey umfal

I had the same issue for 6 months.
Finally resolved the issue today.
I removed the main head unit and there is a fibre optic connection which is behind the head unit which is connected to the most bus ring.
I bought a bypass cable for £3.75 and connected it to the cable.
No more issues with media but my instrument cluster isnt working correctly.
It seens that there is a braek in the most bus loop and by using the cable to bypass the faulty cable i now have media continuously.
If maybe the sane issue you are having

[Umfall]

Thank you NealfromNZ and sam330e for the tips!

The problem was a damaged NBT unit. I got it replaced, coded and everything works like it should