Audi RS3 Infotainment Dead: MOST Bus Network Failure Fix

Had a similar issue with my 2018 S3. Having some experience with car electronics, I initially thought it was just a software glitch, but it turned out more complex. The car diagnostics revealed multiple communication errors in the fiber optics network. The MOST bus system was failing to properly transmit data between control units. After some initial troubleshooting, the workshop found a defective control unit that was disrupting the entire infotainment chain. The repair involved replacing the faulty control unit and reconfiguring the MOST bus system. Total cost was around 1000 Euro, including parts and labor. Since the fix, all systems have been working flawlessly, audio, navigation, and all connected features. Before suggesting specific solutions for your RS3, could you share: Have you noticed any warning messages before the system failed? Does the issue persist after a complete restart of the vehicle? Are there any other electrical systems showing unusual behavior? Did you recently have any work done on the car? This information would help narrow down whether your issue matches what I experienced with the automotive protocol failure in my case.

Latest service was at 75000 KM. You raise good points about the diagnostics. No warning messages appeared before the failure, and the issue remains after multiple restarts. The problem appeared suddenly while driving on the highway. Other electrical systems work normally, and no recent work was done on the car. The car diagnostics at my local workshop showed a failure in the fiber optics ring, with error codes pointing to communication problems in the MOST bus network. Based on your experience, it sounds like I might be facing a similar control unit failure. The workshop provided an initial repair estimate of 1200 Euro for parts and labor, which seems in line with your case. They mentioned the automotive protocol testing alone would take several hours to properly identify the faulty component in the car electronics system.

Thanks for providing those additional details, this definitely sounds very similar to what I experienced with my S3. The sudden failure during highway driving without warning messages, combined with the diagnostic results showing fiber optics ring issues, strongly matches my case. The quoted 1200 Euro repair estimate aligns with what I paid, considering the extensive diagnostic work needed. One thing I learned from my experience, while the MOST bus testing is time-consuming, its crucial for accurately identifying which control unit is causing the communication breakdown. In my case, once the faulty control unit was replaced, the workshop also had to perform a complete system reset of the automotive protocol to ensure all components were properly synchronized. This extra step proved essential for restoring full functionality to the car electronics. Given the matching symptoms and diagnostic results, I would proceed with the repair. The fiber optics network issues rarely resolve themselves, and delaying could potentially lead to additional control unit failures in the chain. Would you mind updating the thread once the repair is completed? It would be helpful to know if your root cause matches what I encountered with the MOST bus system in my S3.

Thanks everyone for the detailed responses. I wanted to provide an update after getting the car back from the workshop. The issue was indeed very similar to what was described. The technicians found that the main control unit for the audio system had failed, disrupting the entire MOST bus system and blocking data transmission to other components. The repair involved replacing the defective unit and reconfiguring the car electronics to restore proper communication across the network. Final cost came to 1150 Euro, which included: Diagnostic testing of the fiber optics network, New control unit, Labor for installation and system reconfiguration, Full testing of all connected components After the repair, all infotainment functions are working perfectly again. The automotive protocol is stable and all systems are communicating properly. For anyone experiencing similar symptoms, definitely get the MOST bus system checked early to prevent potential cascade failures in other connected modules. Thanks again for helping me understand what I was dealing with and confirming that the repair costs were reasonable.