Audi RS6 MOST Bus Failure Kills All Infotainment

I had a very similar issue with my 2017 RS7 last year. I have some experience working with automotive electronics, but this was definitely beyond DIY territory due to the complex bus system architecture. The symptoms matched exactly, complete infotainment failure affecting multiple systems. The car diagnostics showed several communication errors across the MOST bus network. After thorough testing, the workshop identified a faulty control module in the fiber optic ring as the root cause. The repair process involved: Full system diagnostic scan, Testing signal integrity across the MOST bus, Replacing the defective control unit, Reprogramming and coding the new module, Final testing of all connected systems Total repair cost was 1000 Euro including parts, labor and programming. The audio system and all other functions were fully restored after the repair. While waiting for the parts, the workshop kept me updated on the automotive protocol testing they performed to isolate the exact failure point. The car electronics are quite sophisticated in these models, so proper diagnostic equipment is essential. To provide more specific advice for your case: Which specific error codes are you seeing? Have you noticed any intermittent issues before the complete failure? Does the MMI system show any signs of life at all?

Latest service was at 195000km. The error codes pointed to the fiber optics data transmission failure indeed, but my mechanic found that water damage caused corrosion in one of the main control units. The repair required replacing both the damaged control unit and sections of the fiber optic cables in the MOST bus system. The labor costs were higher than expected since they had to remove several interior panels to access the bus system components. Total bill came to 2800 Euro but at least everything works perfectly now. The data transmission is stable and all systems communicate properly through the bus network.

Thanks for sharing those details about the water damage repair. Your experience actually mirrors what I dealt with on my RS7, water intrusion can be devastating to the fiber optics and control units in these cars. While my initial repair seemed straightforward with just the control unit replacement, I later discovered moisture had affected more components than initially detected. The car diagnostics eventually revealed intermittent signal issues in the MOST bus network, requiring additional repairs similar to yours. The high repair cost makes sense given the extensive labor needed to access and replace the affected bus network components. These fiber optics systems are incredibly sensitive, and once corrosion sets in, you really need to replace all potentially compromised sections to ensure stable data transmission. For others reading this thread: water damage to control units and fiber optic cables often requires more extensive repairs than initially apparent. The car diagnostics might only show the primary failure, but a thorough inspection of the entire MOST bus system is crucial to prevent recurring issues.

That water damage turned out to be much more extensive than I initially thought. I appreciate everyone sharing their repair experiences, helped me understand why the costs ran higher than expected. The most frustrating part was the hidden corrosion damage that wasnt obvious from the initial car diagnostics. The audio system and other electronics are working flawlessly now though, so I guess the complete bus system repair was worth the 2800 Euro investment. Just wish the control unit had better water protection from the factory since these MOST bus repairs are so labor intensive. Good to know others have dealt with similar issues in their cars. Will definitely keep an eye out for any signs of moisture around the electronic components in the future.