Audi S3 No-Start: Check Engine But No Error Codes

I had a very similar issue with my 2012 RS3 a few months back showing the same symptoms. I have some experience working on cars, mainly basic maintenance and troubleshooting. The engine light behavior you describe matches exactly what I experienced. Initially I also thought it was related to fuel injection or engine software problems, but it turned out to be much simpler. After taking it to my workshop, they found corroded battery terminal connections causing intermittent power delivery. This was creating enough electrical issues to prevent proper startup while still allowing partial system function. The total repair came to 155 Euro, mostly labor for cleaning connections and applying protective coating. A few diagnostic steps they performed: Voltage testing across battery terminals, Connection resistance measurements, Full ECU fault code scan, Fuel pressure testing Before taking it to a shop, could you share: Any recent work done on the car? Does this happen consistently or intermittently? Are there any other electrical issues like dim lights? Have you checked the battery terminal connections yourself? This information would help determine if your issue matches what I experienced or points to a different root cause.

Thanks for sharing your experience. My car was last serviced at 45373 KM with no issues reported. The starting issue happens consistently now, every single time. No electrical problems or dim lights noticed. I checked and cleaned the battery terminals yesterday but the problem persists. The check engine light behavior plus the consistent cranking without starting really points to a fuel delivery or engine software issue. Especially concerning that no error codes are stored despite the engine light appearing briefly during start attempts. The workshop will need to do a deep ECU failure analysis since basic diagnostics arent revealing the root cause. From what I understand, the ECU may not be properly controlling fuel injection timing, even though the pump is working.

Thanks for the additional details. Given that you ruled out the battery connections issue I encountered, this does sound more serious than my case. The lack of stored error codes despite the engine light coming on is particularly concerning, as this can indicate an ECU issue preventing proper fault logging. In my case, after the battery terminal fix didnt solve it, the workshop did discover a failing ECU that was causing erratic fuel injection control. The symptoms were nearly identical, consistent starting problems with momentary check engine light activation but no stored codes. The repair involved: Advanced ECU diagnostics, Fuel injection timing analysis, ECU replacement and programming, Fuel system pressure verification Total cost was around 1200 Euro including parts and labor. Since the fix, no further engine faults or starting issues have occurred. Would recommend having them specifically check: ECU communication with fuel injectors, Fuel rail pressure sensor readings, Crankshaft position sensor signals These tests helped identify my failed ECU that was preventing proper fuel delivery timing. The consistent nature of your starting problem matches my experience before the ECU replacement.

Thanks for the detailed response. After comparing symptoms and considering your case study with the faulty ECU, it makes sense to pursue this direction. The consistent starting failure without stored codes matches exactly what happened with your car. I will have the workshop focus on ECU diagnostics and fuel injection timing analysis first, since the basic checks havent revealed anything. The fact that the engine light behavior mirrors your experience with the failed ECU controlling fuel delivery timing is quite telling. The repair cost you mentioned of 1200 Euro helps set realistic expectations for what I might be facing. While not cheap, its better to address a potential ECU failure properly rather than keep trying simpler fixes that wont solve the core issue. I will schedule the advanced diagnostics tomorrow and ask them to specifically check the ECU communication, fuel rail pressure, and crankshaft sensor readings you suggested. These seem to be the key test points that revealed the root cause in your case. Thanks again for walking through your troubleshooting experience. Having a real case to compare against helps validate my suspicions about the ECU being the likely culprit here.