VW Polo ECU Failure Causing Power Loss, Owner Tips

Had the exact same situation with a VW Golf TDI from 2018. Being someone with some basic car maintenance experience, I first attempted a system reset using my OBD scanner, but the ECU problems persisted. After multiple attempts at resetting the vehicle electronics, I took it to a workshop where they diagnosed a defective main relay that was causing communication issues with the computer module. Once they replaced the main relay, the control system started functioning normally again, and the engine power returned to full capacity. The repair cost me 120€, including parts and labor. Much better than replacing the entire ECU, which was my initial worry. Before suggesting specific solutions for your case, could you share: Any warning lights on the dashboard? Does the issue occur more during cold starts? Have you noticed any electrical issues before this started? What specific error codes were stored in the system? This information would help determine if your Polo is experiencing the same relay issue or if something else is affecting the ECU.

Last serviced at 140041km, and I can confirm experiencing similar warning lights and performance issues. Connected my OBD reader yesterday and it showed multiple ECU communication errors. The check engine light comes on mainly during cold starts, and I have noticed occasional electrical glitches with the central locking system. The control system shows error codes P0401 and P0402, suggesting issues with the EGR system communication. The automotive electronics definitely seem compromised, as the car also struggles to maintain idle sometimes. Before investing in a new computer module, a relay check sounds like a cost-effective first step to diagnose the issue. These symptoms started appearing gradually over the last two weeks, unlike your sudden onset. Would you recommend getting the relay tested before looking into more expensive repairs?

Thanks for providing those details. Based on those error codes and symptoms, your situation seems slightly different from what I experienced, even though some patterns match. In my case, the ECU communication issues were more sudden, while your gradual onset and specific error codes pointing to the EGR system suggest a different root cause. A system reset might help temporarily, but given the combination of EGR-related codes with electrical glitches, I would recommend checking both the EGR valve and its wiring harness first. For my Golf TDI, the main relay was clearly the culprit because there were no specific system errors pointing elsewhere. The car diagnostics showed general communication errors rather than the targeted EGR codes you are seeing. While testing the relay is still worth doing since it is a low-cost check, the engine performance issues in your case might be more related to a failing EGR valve or its control circuit. When my mechanic performed car diagnostics, they specifically pointed out that clean error codes related to a single system usually indicate a problem with that component rather than general ECU failure. Before spending money on parts, get a professional scan of the vehicle electronics to confirm the exact source of these error codes. My repair turned out simple, but your symptoms suggest you might be dealing with a different underlying issue.

Thanks for sharing those insights about your Golf TDI repair. The fact that my Polo has been showing these issues gradually does make me think the root cause might be different. You make a good point about the specific EGR codes versus general ECU communication errors. After reading about your experience, I will start with a professional diagnostic scan to pinpoint whether the engine control issues stem from the EGR system rather than jumping straight to ECU replacement. The car diagnostics should reveal if the system reset and relay check make sense as first steps, or if I need to focus on the EGR valve and wiring. The electrical glitches with the central locking combined with engine performance problems had me worried about a complete ECU failure, but your case shows how important it is to properly diagnose before replacing expensive components. Will book a thorough scan this week and update once I know more about what is affecting the control system. Good to know your repair ended up being relatively simple and affordable. Hoping for a similar outcome once I get to the bottom of these error codes and performance issues.