Audi RS5 Won't Start After Check Engine Warning

Had similar issues with my 2015 Audi RS7. When the engine failed to start, the initial check engine warning was also present. After proper engine diagnostics, it turned out the battery cable terminals had severe corrosion and loose connections. The starting problem symptoms match closely, engine not cranking properly and intermittent electrical issues. These can mimic more serious engine control problems, which explains the mechanics initial concerns. In my case, cleaning the battery terminals and securing the connections resolved the starting issues completely. For proper troubleshooting, expect: 1. Battery voltage test 2. Terminal connection inspection 3. Starter motor diagnostic 4. Full engine diagnostics scan 5. Fuel injection system check if above tests clear This is generally not a serious repair when caught early, but corroded connections can damage other electrical components if left untreated. The check engine light in this case likely triggered due to voltage fluctuations from poor connections. Would strongly suggest starting with the battery connections before exploring more complex engine fault scenarios. The symptoms align with a classic case of deteriorated battery cables rather than engine control issues.

Thanks for sharing your experience. I had the exact same problem with my RS5, first the check engine light, then complete failure to start. My ECU failure diagnosis initially had me worried, but it turned out to be corroded battery terminals too. The engine software scan showed several faults that disappeared after fixing the connections. How much did the repair cost in your case? Have you had any issues with the electrical system since getting it fixed? My repair was completed a few months ago and everything has been running smoothly with no further engine fault codes.

Just returned to update on the costs since fixing the battery cable issue. The repair bill came to 155 Euro for cleaning and securing all connections properly. The engine control malfunction and related fault codes cleared up completely after the fix. The electrical system has performed flawlessly since then with no engine stalling or startup problems. Those initial engine fault warnings from the ECU were definitely triggered by the poor power connection, not actual engine issues. The repair shop confirmed this is quite common, unstable voltage from bad connections can cause various sensors to report false engine surge and fuel injection errors. Pretty relieved it turned out to be just corroded battery terminals rather than serious engine control problems. Over a year later and the car starts perfectly every time with no warning lights or electrical gremlins. Regular battery terminal maintenance is now part of my service routine to prevent similar issues. Good to hear your RS5 is also running well after the same fix. These false engine fault readings from bad connections seem to be a known quirk with these models.

Thanks everyone for the insights. Just wanted to share how my repair experience turned out. After reading about similar cases, I took my RS5 to a different mechanic who actually listened to the symptoms. The new shop immediately checked the battery connections and found heavy corrosion. They did a complete engine software scan which showed multiple fault codes. After cleaning and securing the terminals properly, the engine started right up and all error codes cleared. Total cost was 180 Euro for diagnostics, cleaning, and new terminal clamps. The check engine light has stayed off and the car starts perfectly now. Much better outcome than the first shop that wanted to replace engine control modules. The whole repair took under 2 hours once they identified the real problem. No engine surge or starting issues since then. Just goes to show how important it is to get a second opinion when the initial diagnosis seems questionable.