VW Touran Audio & Nav Failure Points to MOST Bus Issue

I had a similar issue with my VW Golf from 2006. Having some experience with car electronics, I first suspected individual component failure, but it turned out to be more complex. The symptoms matched yours exactly, complete audio system failure with multiple systems affected simultaneously. The automotive protocol diagnostics revealed a defective control unit in the MOST fiber optics network, which was disrupting all communication between components. After attempting basic troubleshooting like checking fuses and connections, I took it to a specialized workshop. They performed a complete diagnostic scan of the car electronics network and identified the faulty control unit that was causing the cascade failure in the communication bus. The repair involved replacing the defective control unit and recoding the entire system, costing approximately 1000€ including parts and labor. Since then, all systems have been functioning properly. Before suggesting specific solutions for your case, could you provide: Complete error codes from your diagnostic scan, Whether the issue appeared suddenly or developed gradually, If any recent work was done on the electrical system, Whether you notice any other electrical issues This information would help determine if your issue matches the same failure pattern I experienced.

Thanks for sharing your experience. After getting my latest service at 115359km, I also did some basic diagnostics myself. The error codes indicate a potential bus network issue rather than individual component failures. The audio system started behaving erratically before completely failing. The control unit diagnostic readings point to similar symptoms you described. Particularly helpful to know about the MOST fiber optics network issues, as this matches what my initial scan revealed. Would you mind sharing which diagnostic tool was used to identify the specific automotive protocol issues? Also interested if the replacement control unit required any special programming after installation.

Based on my experience with the same issue in my VW Golf, I used a professional-grade diagnostic system that could specifically analyze the MOST bus data transmission protocols. The tool not only identified the faulty control unit but also mapped the entire fiber optics network to pinpoint communication breaks. For the actual repair, the automotive protocol testing revealed that the control unit needed specific programming after replacement. The workshop used a VAS diagnostic system that could properly interface with the car electronics and ensure proper initialization of the new unit. The programming process was critical, without it, the new control unit wouldn't properly integrate into the existing bus system. After installation, they had to: Configure the control unit to the vehicle specifications, Reset all communication parameters, Validate data transmission across the MOST network, Test all connected components systematically One detail I forgot to mention in my previous response: during diagnostics, they found tiny breaks in the fiber optics ring, which contributed to the intermittent failures before complete system shutdown. The comprehensive repair included checking all optical connections in the bus system. The total diagnostic and repair time was about 4 hours, but it was worth it for a permanent fix rather than temporary workarounds that might have caused further issues.

Thank you for the detailed information about the diagnostic process. This helps confirm my suspicions about the MOST bus being the core issue. Your experience with the fiber optics network problems matches my current symptoms perfectly. I will look into getting a proper car diagnostics scan done with a VAS system, since my basic scanner might not be catching all the data transmission issues. The fact that your repair included checking the optical connections is particularly relevant, as my audio system also showed intermittent behavior before failing completely. The cost breakdown and 4-hour repair timeframe gives me a realistic expectation for budgeting the fix. Based on your experience, I will make sure any repair includes: Complete MOST bus diagnostic scan, Inspection of all fiber optics connections, Control unit testing and potential replacement, Full system programming after repairs Before booking the repair, I will gather all my error codes and system behavior documentation to help speed up the diagnostic process. 1000€ seems reasonable for a permanent solution rather than continuing with a non-functional audio system and navigation.