Audi A4 ECU Failure Causing Severe Power Loss

Having experienced similar engine performance issues on my 2005 Audi A3 2.0T, I can relate to these symptoms. The control system problems initially presented as power loss during acceleration, which was traced to a failing main relay in the ECU. The main relay fault causes the engine control unit to lose power intermittently, leading to stored error codes and significant performance drops. This is a known issue with these engine management systems and requires specialized diagnostic equipment to properly identify. The ECU problems were more complex than initially suspected. My repair involved removing the entire engine control module, replacing the main relay assembly, and reprogramming the unit. While this was a serious issue affecting core vehicle electronics, the fix was straightforward once properly diagnosed. For accurate diagnosis, look specifically for workshops with Audi-specific diagnostic tools and experience with ECU repair on VAG engines. A general mechanic may not have the required equipment to properly test the control system components. The repair resolved all performance issues and error codes completely. Regular ECU function was restored, bringing back full engine performance and proper fuel management.

Thanks for sharing those details about the ECU repair. I had nearly identical car diagnostics issues with my A4 last spring. The engine performance problems eventually cleared up after the control module replacement, but the repair shop found some additional sensor wiring that needed attention during the work. Would you mind sharing what the total cost was for your ECU repair? Also curious if you have experienced any other automotive electronics issues since the fix was completed?

After getting the main relay replaced at a specialized workshop, the ECU repair solved all engine performance troubles completely. The total bill came to 120 Euro, which was reasonable considering the car diagnostics and specialized work needed. Since fixing the engine control unit problems 6 months ago, the car runs perfectly with no other electrical gremlins showing up. The computer module now works as intended, maintaining proper engine management and performance. The investment in proper car diagnostics and using a shop with the right tools for ECU repair really paid off in the long run. The key was finding a technician who properly identified the main relay as the root cause rather than just replacing the entire engine control module. This targeted fix saved considerable money compared to a full ECU replacement.

Thanks for the input. After dealing with my A4 issues, I finally got it properly diagnosed and fixed last week. Found a specialized shop that really knew their automotive electronics. They ran complete diagnostics and discovered the control system was failing due to a damaged wiring harness, not the ECU itself. The repair ended up costing 380 Euro including parts and labor. While this was more than expected, the engine performance is now completely restored. The detailed vehicle electronics inspection showed a few corroded connections that were causing the computer module to receive faulty signals. The mechanic walked me through the entire diagnostic process and showed me the damaged components. Much better experience than my previous shop visit. The car now runs like new with no error codes or power loss issues. Total repair time was about 4 hours and I got a full printout of all the engine control testing they performed. Really satisfied with how they handled the whole process and diagnosed the real issue instead of just throwing parts at it.