Audi S8 ECU Failure Causes Complete Engine Shutdown

Had similar issues with my 2019 Audi S6. The ECU failure warning showed up after experiencing unusual engine surge problems. Initially thought it was serious, but the root cause was corroded battery terminals causing poor connections. Main symptoms match your situation: No ECU communication, Complete failure to start, Engine light issues, Diagnostic tools showing no data The fix involved: Cleaning battery terminals, Replacing corroded cable connectors, Checking ground connections, Resetting ECU after repair Important: Poor battery connections can mimic serious ECU issues and engine stalling problems. Before replacing expensive components, have all power connections inspected. The ECU needs stable power to function correctly. Common mistake: Many techs jump straight to ECU replacement without checking basic electrical connections first. Recommendation: Look for a shop specializing in Audi electrical diagnostics. Make sure they perform a complete voltage drop test across all major power connections before replacing parts. This type of issue is straightforward to fix if diagnosed correctly but can be expensive if misdiagnosed as an ECU module failure.

Thanks for this detailed explanation. My S8 had nearly identical symptoms and turned out to be an engine software conflict after a failed update rather than a full ECU failure. The fuel injection system kept cutting out because of the corrupted programming. This really helped point me in the right direction. How much did the repair end up costing you? Have you experienced any other electrical or engine stalling issues since the fix?

Great news on getting the battery connections sorted out. The complete repair came to 155 Euro, which covered cleaning and replacing the corroded cable connections. Since fixing those electrical issues, the engine software has been running perfectly with no more ECU malfunction warnings or engine surge problems. The repair shop did a full check of the fuel injection system while they had it, just to be safe. No engine stalling or starting issues since then. It shows how important proper electrical connections are for modern engine management systems. The diagnostic showed it was much simpler than a complete ECU issue. Good battery connections are crucial for stable engine performance. The engine light hasnt come back on in months of regular driving. Main takeaway: Always start with checking electrical connections before assuming more complex engine software problems. It can save both time and money.

I took my S8 to a specialized Audi shop last week after reading the responses here. The technician found the software conflict in the engine management system that was causing the ECU failure warnings. They performed a complete reset and reload of the engine software which fixed the fuel injection cutting out. Total cost was 380 Euro for diagnostics and reprogramming. Much better than the 2000 Euro+ quoted for a full ECU replacement that another shop suggested. The engine light is now off and the car starts perfectly. No more engine stalling or diagnostic communication issues. The shop also did a full systems check while they had it connected. Really glad I found a mechanic who properly diagnosed the actual problem instead of just throwing parts at it. Cars been running great for the past week with no warning lights or starting problems.