Audi Fault Codes Won't Clear: ECU Memory Lock Issue

Having some experience with automotive diagnostics, I faced a similar issue with my 2010 Audi A4 2.0 TFSI. The car electronics were showing persistent fault codes that wouldn't clear from the active memory. After multiple attempts with different diagnostic tools, my workshop found that the root cause was an undervoltage problem in the vehicle electrical system. The computer system was maintaining fault codes as a protective measure. The battery voltage was dropping below the required threshold, causing the ECU to store these codes permanently. The fix involved: Complete electrical system diagnosis, Testing and replacing the voltage regulator, Recalibrating the car electronics, Properly clearing the fault memory with professional equipment Total repair cost was 240 Euro, including diagnostics and parts. Before suggesting specific solutions for your A5, could you share: Battery age and condition, Any recent electrical modifications, Specific fault codes showing up, Whether you notice any electrical issues (dim lights, slow starter) This information would help determine if your issue stems from a similar undervoltage problem or if there might be other factors affecting the auto repair process.

I had my last service done at 77000 kilometers and the issue started shortly after. My car has 78807 km now, which makes me think it could be related to something they did during maintenance. The control unit might have been affected when they performed the routine computer system updates. Ive noticed the same fault codes keep returning to the active memory within 24 hours after clearing them. Getting quite frustrated with this persistent ECU fault. Will try checking the battery voltage levels as suggested. Will update once I know more.

Thanks for the update. Since I dealt with similar memory lock issues on my A4, I can share that service-related ECU programming can sometimes trigger persistent fault codes. The timing of your issue strongly suggests a connection to the recent maintenance. When my auto repair shop performed the full diagnostics, they discovered that routine software updates can occasionally create conflicts in the car electronics if not completed properly. The fault memory lock might activate as a fail-safe when the ECU detects incomplete programming sequences. Before checking battery voltage, I recommend: 1. Getting the exact service records from your last maintenance 2. Having a specialist perform advanced ECU diagnostics to verify if any programming routines were left incomplete 3. Checking if the workshop used manufacturer-approved software for updates For reference, my A4s issue was resolved by: Running a complete programming cycle, Performing a hard reset of the control modules, Clearing the fault memory with professional equipment This comprehensive fix cost around 180 Euro and permanently resolved the recurring codes. The automotive diagnostics revealed no actual component failures, just a software-related memory lock issue. Let us know what you find regarding the voltage levels and service history. This will help determine if your A5 needs similar reprogramming or if theres a different underlying cause.

Thanks for the detailed response. The service records show they did perform an ECU update during the last maintenance. I checked the battery voltage with a multimeter and its reading normal at 12.6V. The fault codes keep reappearing in the active memory no matter what I try. Called the service center and they confirmed there was an interrupted programming sequence during the last visit. They want 200 Euro to run a complete diagnostics and reprogram the car computer system. Seems like a fair price considering the complexity of these fault codes and ECU issues. Will book it in next week to get the control unit properly reprogrammed. Hopefully this resolves the persistent memory lock and clears those stubborn codes once and for all. Makes sense that incomplete software updates could cause these auto repair headaches. Will post an update after they fix the car electronics.