VW Polo Media System Failure: MOST Bus Network Down

I had a very similar issue with my 2011 VW Golf TDI. As someone with moderate experience working on VWs, I can share what helped resolve this. The symptoms were identical, complete failure of the audio system and infotainment. The data transmission through the MOST bus was interrupted, affecting multiple control units. After extensive diagnosis, the workshop found a defective fiber optics ring controller unit that was disrupting the entire bus system. The repair involved: Complete diagnostic scan of all control units, Testing the MOST bus ring for breaks, Replacing the faulty control module, Reprogramming and coding the new unit, Testing all connected systems Total cost was around 1000€ including parts and labor. Since then, the infotainment and all connected systems have worked flawlessly. Could you share: Have you noticed any warning messages before the system failed? Does the issue occur intermittently or is it constant? Were there any recent repairs or modifications to the electrical system? Did you get specific fault codes from the scan? This information would help determine if your case matches what I experienced and could guide you toward the right fix.

Thanks for sharing your experience. The issue on my car with 70336km is constant, no warning messages appeared before the failure. Car diagnostics revealed fault codes pointing to MOST bus communication errors. Based on your repair details, this gives me hope its fixable without replacing the entire head unit. The symptoms match exactly, complete audio system failure and no functionality in any infotainment features. Will have the fiber optics connection checked, especially since no prior electrical work was done that could have caused this. Main concern is finding a shop with proper diagnostic equipment for the bus system testing.

Thank you for providing those details. Since we have matching symptoms and fault codes, I am quite confident your MOST bus issue is similar to what I encountered on my Golf. After dealing with this myself, here are some key points from my repair experience that might help: The fiber optic ring testing revealed the fault was in the control module, not in the actual optical cables of the bus network. This is actually good news, as replacing damaged fiber optics would be more complex and expensive. Make sure the workshop uses specific automotive protocol testing equipment for MOST bus diagnostics. In my case, some general repair shops could read the error codes but lacked the specialized tools to properly diagnose the car diagnostics system communication issues. Parts cost was around 400€ for the ring controller unit, with labor making up the rest since accessing and programming the unit took several hours. But this was far cheaper than replacing the complete head unit. Looking at your mileage of 70336km, this seems to be a typical point where these bus system failures can occur. My car had similar mileage when the issue appeared.

Thanks for the additional info, feel like I have a much clearer picture now. The similar mileage when the failure occurred and identical symptoms are really helpful data points. Will definitely look for a shop that specializes in bus network diagnostics rather than a general repair place. Good to know I might just need the ring controller unit replaced instead of the whole head unit, which would have been way more expensive. I will call around to find someone with the right car diagnostics equipment to properly test the fiber optics and MOST bus systems. The fact that this was a typical failure point at this mileage and that no prior electrical work was done makes me more confident this is a known issue with a proven fix. Just need to find the right shop with proper testing capabilities for the control unit and bus system communications. Your repair experience is exactly the kind of real-world insight I was hoping to get. Will update once I get it checked out.