Audi SQ8 Engine Cuts Out Due to Start-Stop Glitch

Having moderate experience with Audi vehicles, I encountered a very similar issue with my 2018 Audi SQ7. The symptoms were almost identical, engine stalling during driving and start-stop system acting unpredictably. After multiple instances of the car failing to restart properly, I took it to a workshop. The initial battery test showed normal readings, but a deeper diagnosis revealed the battery was actually failing under load. Even though the car battery appeared fine on basic tests, it was heavily discharged and couldn't maintain proper voltage during start-stop system activation. The repair involved replacing the battery with a higher capacity AGM model specifically designed for vehicles with start-stop systems. Total cost was 290 Euro including programming and registration to the vehicle system. Since then, no more unusual engine shutoffs or starter motor issues. To provide more specific advice for your case, could you share: Current mileage on your SQ8, How long youve had these symptoms, Whether the issues occur more frequently in cold or hot weather, If you regularly make short trips where the start-stop system activates frequently This information would help determine if youre experiencing the same battery issue or if its related to another component in the start-stop system.

Latest service was at 147500 KM two months ago. Thanks for sharing your experience and solution details. After getting the car back from the workshop yesterday, they found it wasnt the battery causing the engine stalling after all. The idle stop sensor had corroded connections and was sending incorrect signals to the engine control unit. The automatic restart issues were triggered by a faulty starter motor relay that was intermittently malfunctioning. Total repair cost was 420 Euro for parts and labor. The car is now running perfectly with no warning lights or unexpected shutdowns. To help others who might face similar symptoms, the repair shop mentioned these issues often get misdiagnosed as car battery problems because the symptoms appear similar. A proper diagnostic scan helped identify the actual failing components.

Thanks for the update on your SQ8 repair. This is really useful info, as I initially thought our issues were identical when you first posted. While my SQ7s problems were battery-related, its interesting to learn how the same symptoms led to a different root cause in your case. The idle stop sensor corrosion is actually a known weak point in these models. The starter motor relay issue you described makes sense too, when these components start failing, they often create similar symptoms to a weak car battery, which explains why techs sometimes misdiagnose it. After dealing with my own start-stop system troubles, I made it a habit to keep the engine control unit connections clean and protected. The eco mode features in these cars rely heavily on proper sensor readings, so even minor corrosion can trigger multiple issues. The 420 Euro repair cost seems reasonable considering the components involved. Much better than having to replace the entire start-stop system, which was initially a concern in both our cases. Did the shop mention any preventive maintenance tips to avoid future sensor corrosion? With my car, regular connection cleaning has helped maintain reliable start-stop operation.

I appreciate the detailed follow-up about the start-stop system issues. You make a good point about preventing sensor corrosion. The repair shop actually recommended checking the connections every 6 months and applying dielectric grease to protect against moisture and corrosion. They also suggested that hybrid vehicle owners particularly need to monitor these systems closely since they rely heavily on sensor accuracy for efficient operation. Since fixing the idle stop sensor and starter motor relay, I've noticed smoother transitions when the engine automatic restart activates. No more engine stalling or warning lights. The shop also updated the engine control unit software as a precautionary measure to prevent any compatibility issues with the new components. For anyone dealing with similar symptoms, I recommend getting a proper diagnostic scan rather than assuming its a battery issue. While battery problems can cause comparable issues, sensor and relay failures are equally common culprits in these engine stalling scenarios. The repair has completely resolved my concerns about reliability, especially during daily commutes with frequent stop-start cycles. My experience shows that addressing these issues promptly helps avoid more extensive system damage. The 420 Euro spent was definitely worth preventing potential long-term problems with the start-stop functionality.