Audi S7 MOST Bus Failure Kills All Entertainment Systems

I had a very similar issue with my Audi S6 2020 last year. Have some experience with car electronics and basic diagnostics, but this was beyond DIY territory. The symptoms matched exactly, complete infotainment failure and multiple error codes. The car diagnostics revealed that the MOST bus system was indeed the culprit. The fiber optics ring that connects the audio, navigation and other control units had a defective component interrupting the signal flow. Took it to a workshop specializing in automotive protocol systems. They used specialized diagnostic equipment to trace the exact failure point in the MOST network. Turned out one of the control units was faulty and needed replacement to restore the fiber optics communication. Total repair cost was 1000 Euro including parts and labor. The workshop had to reprogram and code the new unit to work with the car electronics system. Would help to know: Have you checked if all fuses are intact? Are there any other electrical issues besides infotainment? What specific error codes are you getting? Did this start suddenly or develop gradually? This info would help determine if your issue is identical to what I experienced.

Thanks for sharing your experience. My issue started completely out of nowhere during a regular drive after my last service at 45481 KM. The car diagnostics showed multiple communication errors across the data transmission network. Checked all fuses first, they are fine. No other electrical problems besides the complete infotainment failure. The issue appeared suddenly in the middle of using navigation. The fiber optics diagnostic report shows multiple breaks in connectivity between modules. The error codes mainly point to the MOST bus interface, suggesting a failure in the automotive protocol system rather than individual component issues. Makes sense that a specialized workshop would be needed for this level of bus network repair.

Based on what you describe, this sounds exactly like what I dealt with on my S6. The sudden failure during normal operation combined with those specific data transmission errors matches my experience perfectly. When my MOST bus network failed, the diagnostic report also showed multiple connectivity breaks. The fiber optics system is sensitive, even a single faulty connection point can disrupt the entire ring topology and cause complete audio system failure. In my case, the car diagnostics revealed that while multiple errors were logged, the root cause was actually a single failed control module that corrupted the whole bus network. The workshop confirmed this using specialized protocol testing equipment that could trace signal flow through the fiber optics. Important note: Make sure whoever works on it has experience with MOST systems specifically. Regular scanning tools cant properly diagnose these automotive protocol issues. The repair requires both specialized diagnostic equipment and expertise in car electronics. My advice would be to skip general mechanics and go straight to a shop that specializes in vehicle network systems. Could save you diagnostic time and money in the long run, since my repair journey started with two unsuccessful attempts at regular shops. The multiple error codes appearing simultaneously across different modules is actually a typical indicator of a MOST bus failure rather than individual component issues.

Thanks for the detailed information. After comparing your case with mine, I'm convinced we're dealing with the same type of MOST bus failure. Your repair experience really helps confirm my suspicion about the fiber optics network being the core issue. I've already contacted a workshop specializing in automotive protocol systems and booked an appointment for next week. The specialist mentioned they have the proper car diagnostics equipment to trace MOST bus network failures. The sudden failure during navigation use, combined with the multiple communication errors across the bus system, matches your experience perfectly. It gives me some peace of mind knowing that in your case it was resolved with a single control unit replacement, despite showing multiple errors. Interesting that you mentioned avoiding general mechanics, I actually cancelled my appointment with my regular shop after reading about your experience. No point wasting time and money on diagnostic attempts without the proper equipment for testing fiber optics and audio system connectivity. Will update once the specialized workshop identifies the exact cause of my bus network failure. Hope it turns out to be a similarly straightforward fix like in your case, even if the repair cost is around 1000 Euro.