S6 ECU Fault Code Persists Despite Multiple Fixes

Having experienced a similar issue with my 2003 Audi S4 4.2L, the persistent control unit errors were related to an undervoltage condition in the ECU system. The fault codes kept reappearing even after clearing them through standard diagnostic tools. The auto repair revealed three core issues: 1. Corroded ground connections at the ECU 2. Failing voltage regulator 3. Memory lock caused by voltage fluctuations While the car ran normally, addressing these issues was crucial to prevent potential ECU damage. The repair required: Cleaning and resoldering ECU ground points, Replacing the voltage regulator, Performing a full ECU reset using specialized diagnostic equipment This proved to be a serious issue requiring immediate attention, as continuous voltage fluctuations can permanently damage the control unit. After the repair, all fault codes cleared permanently and the ECU maintained stable operation. The symptoms match closely with your case, suggesting similar underlying electrical issues rather than a complete ECU failure. Getting a voltage analysis of the ECU circuit would be the recommended first step before considering replacement.

Thanks for sharing that detailed repair experience. Your solution with the voltage regulator and ground connections really caught my attention, as similar car electronics issues started showing up in my Audi S6 last month. The automotive diagnostics showed almost identical fault codes. Did you remember the total repair cost for fixing those ECU-related problems? Also, curious if everything has stayed stable since the repair or if youve noticed any new electrical quirks popping up?

Good news, got the voltage issues sorted last week. The computer system diagnostics confirmed it was indeed an undervoltage problem, just like I suspected from my earlier experience. The total repair came to 240 Euro, which covered fixing both the faulty connections and that pesky fault memory lock. The most important update is that after clearing the ECU fault codes, they havent returned. The automotive diagnostics now shows all systems running normally. The fault memory lock issue that was giving you similar headaches is completely resolved. The repair really targeted those unstable voltage readings that were triggering the control unit errors. Based on several months of trouble-free operation in my case, addressing these electrical system faults properly seems to prevent any recurring issues. The ECU diagnostics are now showing stable values, which suggests the fix was comprehensive. No new electrical problems have emerged since the repair, and the control unit is functioning exactly as it should.

Thanks for the input. Just got back from the mechanic and wanted to share how it went. The auto repair took about 4 hours and cost 280 Euro total, which was better than expected for an ECU-related fix. The automotive diagnostics confirmed it was mainly about bad ground connections and a failing voltage regulator, similar to what others mentioned. The mechanic cleaned all the connections and installed a new regulator. They also used specialized equipment to properly reset the ECU diagnostics and clear that stubborn fault memory lock. Really happy to report all fault codes are now gone and everything runs perfectly. The mechanics actual work matched up well with the advice shared here. For anyone facing similar control unit errors, definitely worth checking the electrical connections first before jumping to full ECU replacement. Thanks again for helping point me in the right direction with this repair.