Alfa Audio Dead: MOST Bus System Failure Alert

Been there with my 2003 Alfa 159 Diesel. My experience with automotive electronics is moderate, but this issue was quite specific to the MOST bus architecture. The symptoms were identical, complete audio system failure and navigation blackout. The fiber optics network in these models is indeed sensitive, and the control unit failure you are experiencing is unfortunately common in these Alfas. Had it diagnosed at a specialist workshop. They identified a faulty control unit in the MOST bus system that was disrupting the entire network. Total repair cost was 1000 Euro, which included: Diagnostic testing of the fiber optics ring, Replacement of the defective control unit, System reprogramming, Testing all connected components Before committing to repairs, could you share: Any warning messages showing on the display? Did the issue appear suddenly or gradually? Have you had any recent work done on the electrical system? Does the problem persist after battery disconnect/reconnect? This info would help confirm if your issue matches what I experienced with my 159. The bus system architecture is similar between these models, so the fix might be comparable.

Thanks for the workshop details. At 114938KM, I did notice the issue appeared quite suddenly after my last service. After disconnecting the battery for 30 minutes as suggested, the audio system came back briefly but failed again after a few minutes. No warning messages appear on the display, it simply stays completely dark. The control unit diagnostic you described matches my symptoms perfectly. Will have it checked at a workshop for the bus network integrity. My concerns about unnecessary parts replacement were spot on. Good to know the data transmission issues can be pinpointed to specific components.

Glad I could help with identifying the likely cause. The behavior after battery disconnect is particularly telling, that temporary restoration of function strongly points to the MOST bus control unit, just like in my case. The sudden onset after service is interesting because it matches my experience exactly. In my 159, a minor disturbance to the fiber optics during routine maintenance was enough to trigger the failure. The audio system showing brief signs of life suggests the bus network itself might be intact, but the control unit is failing to maintain stable data transmission. After my repair, I learned these control units often develop issues around the 100000-120000KM mark, so your mileage fits the pattern. The good news is that once properly diagnosed and repaired, the automotive protocol system usually remains stable. My car has run flawlessly for 50000KM since the fix. One thing to mention, make sure the workshop tests the entire bus system before replacing parts. In my case, they initially suspected the amplifier, but proper diagnostics revealed the control unit was the actual culprit in the network.

Thanks for sharing your follow-up experience. The timing correlation with the service visit adds another piece to the puzzle. Given the car electronics match your case so closely, I feel more confident about the repair path now. The data transmission recovery after battery disconnect, even if temporary, is particularly insightful. It really helps narrow down the car diagnostics to the control unit rather than a complete bus system failure. Good point about the typical failure range, my 114938KM definitely fits that pattern. Will proceed with the workshop diagnosis, making sure they perform a complete automotive protocol test before any replacements. Definitely want to avoid the misdiagnosis you mentioned with the amplifier. The total cost seems reasonable considering the complexity of the fiber optics repair. Thanks again for the detailed experience share. Will update once the repair is complete. Hoping for the same long-term reliability you achieved after fixing the control unit.