VW Fault Code Lock Appears After Service Visit

Had a similar situation with my 2016 VW Golf TSI last month. The fault codes appeared right after basic maintenance, showing ECU fault related to undervoltage. The control unit was registering voltage drops, triggering the fault memory lock. The issue required immediate attention since undervoltage can affect multiple vehicle systems. The automotive diagnostics revealed the alternator wasnt providing consistent power to the electrical system. This was causing the ECU diagnostics to record multiple fault codes. The repair involved testing the charging system, replacing the alternator, and clearing the ECU fault codes. Without fixing this, there was risk of damage to sensitive electronic components and potential system failures while driving. This type of electrical system problem is serious and should be addressed promptly. In my case, waiting would have led to more extensive damage to the vehicles electronic systems. The fault memory lock is essentially the control unit protecting itself from voltage fluctuations. The symptoms matched yours exactly, appearing after routine maintenance. Would strongly suggest having it checked by a workshop with proper diagnostic equipment.

Thanks for sharing your experience. I had the same fault memory lock issue with my Suran Spacefox in December. The control unit was showing multiple fault codes and my car also had problems with the power supply. The mechanic found that some wiring was damaged during a previous oil change, causing the computer system to register errors. Wanted to ask, how much did your alternator replacement cost? My active memory codes needed clearing and wiring fix was 380€. Also curious if youve had any electrical issues since the repair?

Just got back from the mechanic last week, good news is the fault memory lock issue is completely resolved now. The computer system diagnostics showed it was indeed an undervoltage problem, but thankfully my alternator was fine. The ECU diagnostics revealed it was actually a loose connection causing intermittent power supply issues. The repair cost came to 240€, which included testing the entire electrical system, fixing the connection, and clearing all the control unit fault codes. Much better than needing a full alternator replacement. Since the fix, the car electronics have been working perfectly with no warning lights or error codes. The ECU fault readings are all clear, and the voltage readings are stable. Been monitoring closely through my own basic diagnostic tool, and everything is running exactly as it should. Your repair cost at 380€ sounds reasonable considering they had to fix damaged wiring. Wiring repairs often take more time since technicians need to trace and repair each affected connection in the electrical system.

Thanks for the update. Glad you got it sorted for less cost than my repair. After taking my car to the mechanic last week, they found the computer system was logging errors due to a damaged wire harness near the oil filter housing. The automotive diagnostics showed multiple fault codes triggered by this single issue. The repair took about 3 hours since they had to carefully trace all the affected wiring. The mechanic cleared the fault memory lock after fixing the damaged sections. Total cost was 380€ including parts and labor. Since then, the ECU fault warnings have completely disappeared and all electrical systems are working normally. Really appreciate everyone sharing their experiences. Having similar repair stories helped confirm I made the right call getting it checked promptly instead of waiting for more issues to develop.