S3 Power Loss & ECU Issues: Diagnostics Guide & Solutions

I experienced similar symptoms with my 2014 Audi A4 2.0T. The sudden power loss combined with check engine light often points to a faulty main relay in the automotive electronics system. When my car showed these exact symptoms, the car diagnostics revealed intermittent power supply to the engine control module. The main relay was failing to maintain consistent power distribution to critical vehicle electronics components. Rather than immediately replacing the entire computer module, the repair involved testing the main relay circuit first. The main relay replacement resolved all symptoms, engine power restored, no more warning lights. This was a moderate repair that required professional diagnostic equipment to properly pinpoint the issue. The root cause typically stems from wear in the relay contacts after years of constant switching. While not a minor issue, its far less complex than a full control system replacement. Its worth having a qualified technician verify the relay condition before considering more extensive repairs. Professional diagnosis is essential here since similar symptoms can stem from multiple points in the engine control system. The computer module itself is usually not the culprit when these specific symptoms appear suddenly.

Thanks for sharing your experience. I had the same power loss problem last month. The main relay fix sounds exactly like what happened in my case too. Works perfectly now after the repair. Did you keep track of the repair costs? My engine control unit repair came to 450 Euro but wondering if prices vary much. Also curious if you had any other system reset procedures needed after the work was done?

I can confirm the main relay repair on my A4 cost 120 Euro including labor. Much more reasonable than a complete engine control unit replacement. Since having the automotive electronics system fixed, engine performance has been flawless with no additional issues. No system reset procedures were needed after the relay replacement. The control system automatically recalibrated once the new relay was installed. The technician did verify all engine control parameters were correct using their diagnostic equipment, but that was included in the standard repair process. The key was catching the faulty relay early before it could cause any damage to other components. Regular maintenance and prompt attention to warning signs helps avoid more expensive repairs down the line.

Thanks for the input. Just wanted to close the loop on my S3 situation. After visiting my mechanic, the car diagnostics confirmed it was indeed the main relay causing the power loss. Total repair came to 180 Euro including parts and labor, definitely beats replacing the whole control system. The repair was quick and straightforward. They tested the vehicle electronics, swapped the faulty relay, and ran a final check on engine performance. No extra resets or procedures needed. Car has been running perfectly for the past few weeks. Really glad I checked here first before assuming the worst about the computer module. The early warning signs definitely helped catch this before it turned into a bigger issue. Going to keep a closer eye on regular maintenance to hopefully avoid similar surprises in the future.