Mercedes M Klasse Audio and Navigation System Failure

A MOST bus fault sounds familiar. I had a similar problem with my M Klasse: dead audio, no navigation, the works. Did you run a full car diagnostics scan? What specific error codes did it show? Are other systems that rely on data transmission working? Any issues with the instrument cluster display or climate control? Knowing which modules are affected and the specific communication errors can help pinpoint the faulty unit. This bus system uses a fiber optic cable that loops through all the modules. If one module doesn't transmit data correctly, it can disrupt the entire network. Did you check if all the connectors are properly seated?

Thanks for the detailed response. I will get the exact error codes from the car diagnostics report. The instrument cluster and climate control seem to be working fine. You mentioned the fiber optic cable – can I visually inspect these connectors for damage or disconnections without special tools?

Checking the connectors is a good start. They're usually behind the head unit, amplifier, and navigation unit, so you'll need to remove those to access them. Look for any obvious damage to the fiber optic cables or loose connections. Given that other systems seem fine, I'd suggest a proper car diagnostics with a Mercedes-specific tool at a workshop. It could save time and prevent further problems. They should be able to isolate the faulty module on the MOST bus faster. The cost could be around 1000€.

I appreciate the advice. I followed your suggestion and went to a workshop with specialized car diagnostics equipment. The error was traced to a faulty amplifier within the MOST bus. After replacing it, the system is now working. Thanks for pointing me in the right direction.