Q8 Power Loss and Check Engine Light: Real Fix Needed

I had a very similar issue with my 2019 Q7 last year. I have some experience working on cars but mainly stick to basic maintenance. When the check engine light came on and the engine lost power, I first used my vehicle diagnostics tool which showed multiple fault codes related to the ECU. The car computer was throwing errors about boost pressure and fuel mapping. The root cause turned out to be faulty chip tuning that had been installed by a third-party shop before I owned the car. The engine mapping was causing conflicts with the factory settings. After connecting to the car computer, the workshop found corrupted data in the ECU. The fix involved completely resetting the engine management system back to factory settings and removing all aftermarket performance modifications. Total cost was 180 Euro for diagnostic work and ECU reprogramming. The car has run perfectly since then with full power restored. To better assist with your Q8 situation, could you share: Have any performance modifications been made to the car? What specific fault codes is your scanner showing? Did you notice any other symptoms before the power loss? Is the engine running rough or just lacking power? This information would help determine if your engine issue stems from similar causes or requires different solutions.

I had this power loss issue resolved under warranty at my last service at 192063 KM. In my case, the car diagnostic test revealed the problem was related to a failing fuel pressure sensor that was causing the engine control unit to run in safe mode. The check engine light triggered multiple fault codes pointing to fuel delivery problems. After replacing the faulty sensor and clearing the car computer, normal power was fully restored. No engine damage occurred since the safety systems worked as designed. A visual inspection also uncovered a small vacuum leak that was contributing to the reduced performance. Both issues were addressed at the same time. The car now runs perfectly with proper acceleration and no warning lights on the dashboard. Worth checking these components if your symptoms match. They are known weak points in these engines that can trigger limp mode.

Thanks for providing those details about the fuel pressure sensor fix. My Q8 had very similar symptoms but turns out the root cause was different. The vehicle diagnostics revealed fault codes related to the throttle position sensor, which was causing the car computer to limit engine power as a safety measure. The scan tool showed erratic voltage readings from the sensor. After replacing the throttle position sensor and clearing the check engine codes, full power was restored. The total repair cost was around 450 Euro including parts and labor. Like your case, no engine damage occurred since the failsafe mode activated properly. This seems to be another common failure point on these engines that can trigger reduced power mode. The diagnostic code patterns can help pinpoint whether its a fuel delivery issue like yours or a throttle control problem like mine. Regular check engine light scans during maintenance could help catch these sensor issues before they cause performance problems. Preventive replacement of aging sensors might be worth considering around the 150000 km mark.

Thanks everyone for the detailed feedback on the power loss symptoms. After getting my Q8 properly diagnosed, the issue turned out to be unrelated to sensors, it was actually a clogged catalytic converter causing excessive backpressure. The engine issue triggered multiple fault codes that initially pointed toward fuel system problems. The auto scanner showed catalyst efficiency below threshold, which explained the sudden power loss. The car computer had activated limp mode to prevent engine damage. After replacing the catalytic converter and clearing the check engine light, full power was restored immediately. The repair cost was 1200 Euro but worth it to have the car running properly again. Good reminder that vehicle diagnostics alone dont always tell the complete story, the shop had to do additional testing to confirm the clogged catalyst was causing the performance problems. For anyone else experiencing similar sudden power loss, definitely get a complete diagnostic workup rather than just relying on fault codes. What seems like a sensor issue could be something more significant in the exhaust system.