RS7 Infotainment Failure: MOST Bus System Dead

Had the same MOST bus system failure in my 2015 S6. The fiber optic ring that connects multiple control units stopped communicating properly, causing complete infotainment shutdown. Car diagnostics revealed a faulty control unit in the system chain. The issue required specialized testing equipment to identify the exact break point in the bus network. Main symptoms matched yours, dead MMI screen, no audio, multiple electronic faults across connected systems. The repair involved replacing one defective control unit and checking all fiber optic connections in the MOST ring. This was definitely a serious electrical issue that needed proper dealer-level diagnostic tools to resolve correctly. These failures are somewhat common in vehicles with complex bus networks once they pass 150000KM. The root cause is often degradation of the optical connections or control unit failure rather than simple wiring issues. Recommend having this diagnosed at a shop with proper automotive protocol testing capabilities, as attempting DIY repairs on fiber optic systems often leads to more damage. The repair requires specific tools and expertise in car diagnostics.

Thanks for the detailed response about the MOST bus system failure. This matches my symptoms exactly, the faulty control unit seems to be the likely culprit in my RS7 too. The complete shutdown of the infotainment matches what you experienced. Currently waiting for an appointment with a specialist who has proper car diagnostics equipment. Since you went through this already, do you remember roughly how much the repair cost you? Also wondering if youve had any other automotive protocol issues pop up since getting it fixed? Appreciate the warning about not attempting DIY repairs on the bus network. Definitely planning to leave this one to the professionals with proper testing equipment.

Just got back from having this exact repair done last week, the automotive protocol specialist confirmed it was indeed a faulty control unit disrupting the MOST bus system. The total repair came to 1000 Euro, which included full diagnostics and replacing the defective unit. The good news is the audio system and all connected electronics are working perfectly now. The repair shop used specialized testing equipment to verify the entire bus system was communicating properly after the fix. No more error codes or malfunctions since the control unit replacement. This type of car electronics issue really needs proper diagnosis and repair. The investment in getting it fixed by a qualified technician was worth it to restore full functionality to the infotainment and connected systems. The fiber optic connections in the MOST network are all stable now, and I havent seen any new faults in the bus system since the repair. A proper fix by specialists who understand these complex automotive protocols is crucial for long-term reliability. When done correctly, these repairs typically resolve the issue completely.

Wanted to update everyone on how this got resolved, finally got the RS7 fixed after finding a shop specializing in automotive protocol diagnostics. Their testing equipment picked up exactly where the data transmission was failing in the bus network. Turns out my control unit was completely dead, blocking all communication in the MOST bus system. The repair cost came to 1200 Euro including full diagnostics and parts. More than expected but worth it to have working electronics again. The shop thoroughly tested all fiber optic connections in the bus network after installing the new unit. Everything is back to normal now, navigation, audio, and all car electronics are functioning perfectly. No more error codes or system failures. Really glad I didnt try any DIY fixes on the data transmission components. Having proper diagnostic equipment and expertise made all the difference in getting this resolved correctly the first time. The bus system is now working exactly as it should.