Audi A5 Starting Dead Despite Clean Diagnostic Codes

Had a similar issue with my Audi A4 2004 with the 2.0T engine. The symptoms matched exactly, engine turning over but no start, following previous ECU repairs. The root cause in my case was not actually the ECU but corroded battery terminals causing inconsistent power delivery to the fuel injection system. The engine surge and starting problems were misleading, as they mimicked ECU failure symptoms. The fix required cleaning and replacing both battery terminals, plus checking all ground connections. The mechanic also tested the fuel pump relay since poor electrical connections can prevent proper fuel delivery at startup. This type of electrical issue can be quite serious if left unchecked, as intermittent power supply can damage the ECU and fuel injection components over time. Engine diagnostics initially showed no codes because the power interruption was too brief to register. Worth checking these basic electrical connections before assuming another ECU issue. Have the charging system and battery load tested too, as weak battery output can cause similar symptoms even with good connections.

Thanks for sharing your experience. I had a very similar problem with my A5 last winter and based on your description, it really sounds like it could be the same electrical issue. The check engine light kept coming on out of nowhere before it finally refused to start. Did you remember approximately how much the repair cost in your case? Just curious if the fix was relatively straightforward once they identified the problem. Also wondering if youve had any starting problems or engine software issues since getting it repaired?

Really glad to help! After getting the electrical connections fixed, the car has been running perfectly with no more engine control malfunctions or starting issues. The repair was quite straightforward once they identified the corroded battery connections as the root cause. The total repair came to 155 Euro for cleaning and replacing the battery terminals plus checking all ground connections. Much cheaper than I initially feared, especially compared to potential ECU replacement costs. The check engine light that was out of nowhere appearing completely stopped after the fix. No more engine software glitches or false ECU failure warnings either. The mechanic explained that poor electrical connections can create all sorts of misleading symptoms that mimic more serious issues. If your symptoms match what I experienced, definitely worth having the electrical connections checked before exploring more complex solutions. Good battery connections are crucial for proper ECU and fuel system operation.

I finally took my A5 to the mechanic yesterday based on your advice about checking the electrical system. Turned out you were absolutely right, the main issue was severe corrosion on the battery terminals and a loose ground connection. The repair was quick and straightforward. They cleaned all electrical contacts, replaced both battery terminals, and double-checked all ground points. Total cost was 180 Euro including diagnostic time. The engine starts perfectly now with no more unusual stalling or check engine warnings. What really surprised me was how such a simple electrical issue could cause so many confusing symptoms and engine fault warnings. The mechanic showed me how the corroded connections were interrupting power to the fuel injection system, making it seem like an ECU problem. Makes sense why the engine diagnostics were inconclusive before. Really glad I checked this first instead of jumping straight to expensive ECU repairs. The car runs better than it has in months.