S7 ECU Fault Memory Lock Causing Persistent Codes

I dealt with a very similar issue on my 2011 S6 last year. I have some experience working on cars but ECU diagnostics are definitely not my strong suit. The fault codes kept reappearing instantly after clearing, which turned out to be caused by undervoltage in the vehicle electrical system. The automotive diagnostics revealed that the battery voltage was dropping below critical levels, causing the ECU to enter a protective memory lock state. The workshop had to: 1. Run a complete voltage check across the electrical system 2. Test the alternator output 3. Verify battery health 4. Check for parasitic draws Total repair cost was 240 Euro, including diagnostics and fixing the underlying voltage issue. Getting it fixed at a specialized workshop was worth it since they had the proper diagnostic equipment to pinpoint the exact cause. Before suggesting more specific solutions, could you share: Current battery age and condition, Whether you notice any electrical issues (dim lights, slow starter), If any aftermarket electronics were installed recently, The specific fault codes showing up in your active memory This would help determine if your issue is similar to what I experienced or if its coming from a different source.

Thanks for sharing your experience. Just to update my details: last service was done at 36222 KM. The control unit fault codes in my case turned out to be related to a failing voltage regulator on the alternator, not just a standard battery issue. The auto repair shop first suspected normal battery drain but automotive diagnostics showed the alternator was outputting inconsistent voltage. The ECU diagnostics also revealed the memory lock was engaging to protect sensitive electronics from power fluctuations. After replacing the voltage regulator and running a full system reset, all fault codes cleared permanently. Would recommend getting the alternator tested specifically, beyond just basic battery checks. The fix cost 580 Euro including parts and labor.

Interesting update regarding your alternator voltage regulator. That matches my experience exactly, I initially thought it was just a battery drain issue too, but the computer system was actually protecting itself from those voltage spikes. After getting my S6 fixed, I installed a voltage monitoring system that connects to my phone. It shows the alternator output stays steady now between 13.8-14.2V at idle. The control unit hasnt logged any new fault codes since the repair. The auto repair cost was higher in your case, but replacing the whole regulator assembly probably makes more sense long-term than just doing basic repairs. These cars ECU fault protection systems are quite sensitive to voltage fluctuations. One suggestion, if you havent already, have them check the ground connections while everythings apart. Poor grounding can cause similar symptoms and its a common issue that can make the car electronics act up even with a good alternator. Would be interested to hear if your voltage stays stable now. On my S6, it took about a week of driving before all the adaptive memory settings normalized after the repair.

Thanks all for the input. After 2 weeks of driving since the voltage regulator replacement, I can confirm the auto repair completely resolved my issues. The computer system is running perfectly with no more fault codes appearing in active memory. For anyone searching with similar problems: my control unit was going into memory lock because the failing voltage regulator was causing unstable power delivery. The diagnostic scan showed voltage fluctuations between 11.8V-15.2V which triggered the ECU protection systems. Final cost breakdown of my repair: Voltage regulator: 320 Euro, Labor: 260 Euro, Diagnostic fees: waived since I got the repair done there Important learning: When the control unit shows persistent faults that return instantly after clearing, check the charging system before assuming ECU problems. A proper auto repair shop with good diagnostic equipment can usually pinpoint if its a voltage issue pretty quickly. Will update this thread if anything changes, but so far all systems are working as they should.