Audi A4 Won't Start: ECU & Fuel System Troubleshooting

Had a similar situation with my 2005 Audi A6 2.0T. The symptoms started with intermittent engine stalling and difficulty starting, particularly during cold mornings. After several failed starts, the engine diagnostics revealed multiple fault codes pointing to electrical issues. The root cause was corroded battery terminals and a loose ground cable connection. While this might sound simple, poor electrical connections can trigger ECU issues and create misleading fault codes that suggest fuel injection problems. The electrical system needs proper voltage to maintain stable engine diagnostics and fuel injection control. The repair involved cleaning the battery terminals, replacing the corroded cable ends, and securing all ground connections. After fixing these connections, the ECU needed a reset to clear the stored fault codes. The engine stalling issues disappeared completely after this repair. This kind of problem can often be misdiagnosed because the symptoms mimic more serious engine control issues. A proper diagnosis should always start with checking the electrical system fundamentals before moving to more complex engine diagnostics. If left unaddressed, poor electrical connections can potentially damage the ECU and other electronic components. A thorough check of all electrical connections should be your first step before exploring more expensive repairs.

Thanks for sharing that experience with electrical issues. Mine turned out to be similar, engine light kept coming on and the engine surge symptoms matched what you described. Had the same ECU failure codes initially, but the mechanic found it was indeed the ground wire connection causing the engine fault codes. Did you remember roughly what the repair cost? Also curious if you have experienced any similar electrical issues since getting it fixed? My Audi has been running fine after the repair but I want to stay ahead of any potential recurring problems.

Thanks for the follow-up about your Audi. Glad to hear you got similar results with the electrical fix. The repair bill for my A6 came to 155 Euro, which covered cleaning and fixing the battery cable connections. The engine light and ECU failure warnings cleared up right after. Since getting the ground connections fixed, the engine control system has worked perfectly, no more false engine diagnostics or starting issues. Going on 2 years now without any electrical problems coming back. The key was making sure all the connections were properly cleaned and secured. The engine software is quite sensitive to voltage fluctuations, so good battery connections are crucial for preventing those misleading check engine codes. Regular checks of the battery terminals and ground points during routine maintenance should help catch any issues early.

Thanks for the advice. Got everything sorted now. Took it to a different mechanic who actually found the loose ground connection right away. Total repair only came to 120 Euro including parts and labor, way better than the 500 Euro the first shop quoted for unnecessary ECU work. The engine light turned off as soon as they fixed the connection and cleaned the terminals. Car starts perfectly now, even on cold mornings. No more engine stalling or weird electrical issues. Will definitely keep an eye on those ground connections during future maintenance. Just wanted to close the loop here since your suggestions helped point me in the right direction. Having the right diagnosis made all the difference.