SQ8 Starting Failure Points to ECU Issues

I experienced similar symptoms with my 2017 Audi S7. The starting issue turned out to be much simpler than suspected ECU failure. After thorough diagnosis, the problem was traced to corroded battery terminals and loose connections. The check engine light flash during start attempts is often misleading in these cases. While the ECU might register various faults, the root cause is typically poor power delivery from the battery to the starter system. The fix required cleaning the battery terminals, replacing the corroded connectors, and ensuring proper terminal tightness. These connection issues can trigger multiple electronic faults since modern vehicles need stable voltage for all control modules to function correctly. This is not typically a serious issue, but it can mimic symptoms of more severe problems like engine stalling or ECU failure. The key is proper diagnosis, fuel injection and other systems might show errors simply due to insufficient power supply. For reference, many Audi models share similar electrical architecture, so these symptoms are quite common across the product line when battery connections degrade.

Thanks for sharing your S7 experience. Mine was pretty similar, started with what looked like an ECU issue but ended up being connection related. Would you mind sharing how much the repair cost in your case? After my initial fix, I had some intermittent engine stalling for about a week but that seems to have resolved itself once all the electronics fully reset. Did you experience any lingering issues after your repair?

Had my Audi S7 fixed last week and happy to report no more engine control malfunctions since then. The repair was straightforward, 155 Euro for cleaning and fixing the battery cable connections. Much better than the potential cost of ECU replacement. Unlike your experience, I had no engine stalling after the fix. The engine diagnostics came back completely clean once the proper voltage was restored. The fuel injection system and all electronic components now work flawlessly. The key was making sure all connections were properly cleaned and secured. Sometimes engine surge or starting issues can persist if even a single connection is slightly loose, but a good mechanic will test everything thoroughly. The investment was worth it, no more check engine light or starting problems. These electrical gremlins can be tricky to diagnose but often have simple solutions when properly addressed.

Finally got it sorted after taking it to a different mechanic. The repair was similar, bad connections causing havoc with the electrical system. Total cost came to 180 Euro including a full diagnostic scan. The mechanic showed me the corrosion buildup on the terminals, it was pretty bad. The engine software needed a reset after fixing the connections, which explained my temporary engine stalling issue. The new shop did a thorough job checking all electrical connections, not just the obvious ones. No more check engine light and the car starts perfectly now. Definitely learned my lesson about getting a second opinion. The first shop kept pushing for expensive ECU repairs when it was just basic electrical maintenance needed. At least it was a relatively cheap fix in the end.