VW Beetle Power Loss: ECM Problem vs Other Causes

As someone with moderate experience in car repairs, I faced a similar issue with my 2012 VW Golf. The symptoms you describe match what I encountered, sudden power loss and engine control system warnings. The automotive electronics can be tricky to diagnose, but in my case, the main relay was failing intermittently, causing ECU problems and engine performance issues. After running car diagnostics, the workshop found that the relay was sending inconsistent signals to the control system. The repair took about 2 hours and cost 120€, including parts and labor. The mechanic first performed a full diagnostic scan, then tested the electrical connections before identifying the faulty relay. After replacement, the engine performance returned to normal and all error codes cleared. To better assist with your specific case, could you share: Current mileage, Any recent repairs or maintenance, Specific error codes showing up, Whether the issue occurs more frequently when the engine is hot or cold, If you notice any other electrical issues like flickering lights or difficulty starting These details would help determine if your Beetle is experiencing the same relay issue or if there might be other factors affecting the engine control module.

Thanks for sharing your experiences. My last service was just 2 weeks ago where they did routine maintenance and everything checked out fine. The issue started suddenly after that. I have the exact error codes from my OBD reader: P0172, System too rich P0300, Unusual misfire detected The problems occur consistently regardless of engine temperature. No other electrical issues noticed, starts fine and all lights work normally. Looking at the service history, no previous ECU problems or similar power loss issues were documented. Given the timing right after the service, could something have been overlooked or disturbed during the maintenance work? The vehicle electronics seem to be functioning otherwise, but the engine performance is definitely compromised.

Thanks for providing those details. Your situation seems different from my relay issue, especially with those specific error codes. After seeing P0172 and P0300, I suspect the service work might have inadvertently affected your fuel system rather than the ECU being faulty. On my Golf, I had similar engine performance problems after a service once, but it turned out to be a loose connection at the mass air flow sensor that was disturbed during maintenance. The system reset cleared the codes temporarily but they returned until the connection was properly secured. The combination of system too rich and unusual misfires often points to: Disturbed or damaged vacuum lines, Incorrectly seated connections on fuel system components, Contaminated or failing oxygen sensors, Air intake system issues Before investing in expensive ECU repair, have the shop check these simpler issues first. These components are often handled during routine service and could explain the timing of your problems. Would you be able to check if the engine performance changes at all when you disconnect and reconnect the mass air flow sensor? This quick test might help narrow down whether we are dealing with a sensor issue or a deeper control system problem.

The mass air flow sensor test was definitely worth trying. I disconnected and reconnected it, but saw no change in performance. I took your advice though and had the shop do a thorough check of the vacuum lines and connections first. Turns out you were right, they found a vacuum line that had worked loose during the recent service. It was causing incorrect readings in the car diagnostics system, which made the computer module adjust the fuel mixture incorrectly. The engine control system was actually working as designed, just responding to faulty input data. The fix only cost 80€ and took about an hour. They also did a full computer reset after fixing the line to clear the error codes. Engine performance is back to normal now and no more warning lights on the dashboard. Really appreciate the suggestion to check the simpler issues before jumping to expensive ECU repairs. Saved me quite a bit of money and stress. The vehicle electronics are all working properly now that they're getting accurate sensor readings.