VW Jetta Audio Dead: MOST Bus Network Failure Fix

I had a nearly identical issue with my 2004 VW Passat TDI. As someone with moderate experience working on VWs, I can share that MOST bus failures can be tricky to diagnose without proper diagnostic equipment. The symptoms were exactly as you describe, complete failure of audio and navigation, with multiple stored errors in the control unit. After some initial troubleshooting, I took it to a specialized workshop that deals with car electronics and fiber optics systems. They performed a complete diagnostic of the MOST bus system using specialized equipment to test the fiber optic ring. Turned out one control unit was defective and had interrupted the entire communication loop. The repair involved: 1. Full system diagnostic scan 2. Testing fiber optic signal strength 3. Replacing the faulty control unit 4. Reprogramming the new unit 5. Final testing of all multimedia functions Total cost was 1000€, which included parts and labor. The system has worked flawlessly since the repair. To provide more specific guidance for your case, could you share: Have you performed any diagnostic scans? Are there any visible damage to wiring or connections? Does the system occasionally work or is it completely dead? Which specific error codes are stored?

Thanks for the detailed response. My latest service was just 2 weeks ago, and it started failing right after. The data transmission is completely dead now with no intermittent function. The car diagnostics showed error code 01042 which points to the audio system failure. I checked all visible connections but found no obvious damage to the bus system wiring. The workshop quoted 1200€ for repairs without a clear diagnosis of the root cause, which seems steep. Will try getting a second opinion from a shop specializing in control unit repairs.

Thanks for the additional details. Since my Passat repair, I learned that audio system failures right after service can often indicate accidental damage to the MOST bus connections during maintenance work. The error code 01042 is consistent with what I experienced before my repair. Based on the timing of your issues, I suggest having the shop that did the recent service inspect their work. They might have inadvertently disturbed or damaged a fiber optic connection. The quoted 1200€ does seem high without a proper car diagnostics assessment, especially if the issue was service-related. Getting a second opinion from a control unit specialist is smart. When I dealt with my MOST bus fault, the specialist shop charged significantly less because they properly diagnosed the exact failure point in the automotive protocol chain rather than suggesting wholesale component replacement. A complete system scan using proper diagnostic equipment would determine if its truly a faulty control unit or just a damaged connection. In my case, what initially seemed like a total system failure was resolved by fixing one connection point, costing much less than replacing components. Would also recommend requesting a detailed diagnostic report showing all communication breaks in the MOST bus system before approving any repairs.

I appreciate this thorough advice about MOST bus diagnostics. You make a good point about checking with the original service shop first, I hadn't considered they might have accidentally damaged something during the recent maintenance. The fiber optics in these systems are quite delicate after all. I contacted the original workshop and they agreed to perform a complete data transmission diagnostic at no cost, given the timing of the failure after their service. They'll use specialized equipment to test the entire automotive protocol chain and provide a detailed report of any communication breaks in the control unit network. If they find they caused the issue, they'll handle repairs under their service warranty. If not, I'll still have proper diagnostic results to take to the control unit specialist for a second opinion. This should help avoid paying 1200€ for potentially unnecessary component replacements. Makes much more sense to pinpoint the exact audio system failure point before proceeding with repairs. Will update once I have the diagnostic results and know whether it's a damaged connection or actual component failure.