Audi Q3 Diesel Power Loss: ECU Issues and Fixes

The symptoms match what I experienced with my 2015 Audi A4 2.0 TDI. Initial car diagnostics revealed multiple stored errors, and the reduced power mode was triggered by a failing main relay, which directly impacted the ECU functionality. The repair involved systematic testing of the vehicle electronics, particularly the power supply to the engine control unit. The main relay was found defective, causing intermittent power supply issues to the ECU. This explained both the stored error codes and reduced engine performance. The fix required replacing the main relay and performing a complete system reset. While not the most expensive repair, its quite crucial as a faulty relay can cause cascading issues with engine performance and potentially damage other electronic components if left unaddressed. The key is finding a shop with proper diagnostic equipment. A specialist familiar with VAG car diagnostics would be ideal, as generic scanners might not catch the specific communication issues between the relay and ECU. After repair, full power was restored and all error codes cleared. The entire diagnosis and repair process took about 3 hours. This is definitely something that needs professional attention, but its typically not a catastrophic issue if addressed promptly.

Thanks for sharing your experience. Your case sounds exactly like what Im dealing with. Did you remember the total cost for the repair? Since its been a while since you had it fixed, has everything stayed working properly with the engine performance, or have you noticed any other electrical gremlins popping up? My Q3 seems to be showing similar control system issues and Im trying to budget for the worst case scenario. The automotive electronics in these cars can get pretty complex, so Im hoping its just the relay like in your case and not the entire ECU that needs replacement.

Since having the engine control unit issue resolved at the mechanic, everything has worked flawlessly. The total repair cost came to 120 Euro for replacing the defective main relay, which was significantly less expensive than replacing the entire ECU. The car diagnostics confirmed it was indeed just the relay causing the problems with the control system. The vehicle electronics have performed perfectly since the repair, with no additional electrical issues appearing. The engine performance returned to normal immediately after the system reset, and all error codes cleared permanently. Its been reassuring to see that fixing the main relay resolved all the symptoms completely. This turned out to be a much simpler fix than initially feared, especially considering how complex modern car diagnostics can be. Your Q3 showing similar symptoms likely points to the same root cause, which should be equally straightforward to resolve.

After getting your input about the relay issue, I finally took my Q3 to a specialized shop last week. The technician found the same problem with the main relay affecting the automotive electronics. Cost me 150 Euro for the part and labor, plus 80 Euro for the computer module diagnostics. The repair process went smoothly, they had it done in about 4 hours. After the system reset and a test drive, the engine control unit was working perfectly again. The reduced power issue disappeared completely, and the car runs like new. Really glad I asked here first. Would have probably spent way more if I had gone in blind. The vehicle electronics are all working great now, and the engine has its full power back. Definitely worth finding a shop that knows their way around these control systems. Appreciate everyone who helped point me in the right direction. This turned out to be a much cheaper fix than I had feared.