Audi TT ECU Failure: Clicking Sound, No Start Issue

Had a similar ECU issue with my 2016 Audi S3. As someone with some experience working on cars, I first thought it was a major engine fault that would require expensive repairs. The check engine light and clicking sounds matched exactly what you describe. After taking it to my regular workshop, it turned out the battery cable connections were corroded and loose, causing inconsistent power supply to the ECU. This triggered multiple engine fault codes and made the ECU behave erratically. The fix was straightforward, cleaning and properly securing the battery connections. Total cost was 155 Euro including diagnostic time and labor. The whole repair took about an hour. Before suggesting more specific solutions, could you share: Have you noticed any corrosion around the battery terminals? Does this happen more often after rain or in humid conditions? When was the last time the battery connections were checked or cleaned? Are there any other electrical issues like dim lights or slow power windows? The fuel injection and other systems might appear faulty due to poor power supply, but its worth checking these basic connections before assuming a full ECU failure.

Thanks for sharing your experience. My car has 25191 KM and had its last service 3 months ago. Yes, I notice this tends to happen more in damp weather. The battery terminals look clean but I havent specifically checked for corrosion. The engine diagnostics also showed multiple error codes which matches your experience with power supply issues. No other electrical problems noticed, but the engine surge right before shutdown was concerning. The engine light pattern you described sounds identical, it flashed briefly before the car refused to start. Do you think its worth getting the connections cleaned and checked before going for a full engine software diagnostic? The workshop quoted 290 Euro just for the initial ECU testing.

Your battery connection diagnosis was spot-on. After fixing mine, I discovered other Audi owners reporting similar engine fault symptoms during wet weather. The ECU issues clear up completely with proper battery maintenance. Looking at your mileage and service history, this definitely sounds like a power supply problem rather than a full ECU failure. The multiple error codes and engine light behavior is textbook for inconsistent power delivery to the engine control unit. Save yourself the 290 Euro diagnostic fee. Start with having the battery connections thoroughly cleaned and secured. Make sure they check the ground straps too, on these models they can work loose and cause similar engine stalling symptoms. My mechanic now includes this in regular maintenance after seeing so many ECU-related complaints resolved by proper battery connection service. If cleaning the connections doesnt solve it, then consider the full engine software diagnostic. But from experience with these Audis, when the engine fault messages appear together with starting issues in damp conditions, its almost always related to power supply rather than actual ECU problems. Ask your shop to check the battery cable routing too. Sometimes the insulation wears through where it contacts metal parts, causing intermittent shorts that trigger engine control malfunctions.

Thanks for the advice. After reading about similar experiences, I'll definitely start with checking the battery connections before paying for expensive ECU diagnostics. The correlation with damp weather and multiple error codes appearing suddenly makes the power supply theory very convincing. Going to have my mechanic clean and inspect all battery connections and ground straps first. Much better than spending 290 Euro upfront on engine software testing. Will update once I know more, but feeling less worried now that this might be a simpler fix than a complete ECU failure. The engine light and starting issues match exactly what others described with power supply problems. Just hoping a good cleaning and tightening of connections resolves these engine fault messages. Appreciate all the detailed suggestions, helped narrow down where to start with the repairs. Makes sense to rule out basic electrical issues before diving into complex engine control unit diagnostics.