Q5 Turbo Failure: Power Loss and Hissing Under Load

Had identical symptoms with a 2015 A6 3.0 TDI last year. The turbocharger system was experiencing inconsistent boost control due to a faulty electrical bypass valve actuator. The main indicators matched perfectly, power loss, whistling under load, increased fuel consumption, and unstable idle. The actuator valve controlling the wastegate was not maintaining proper boost pressure, causing the turbo system to underperform. This triggered the engine management system to enter a safe mode, explaining the power reduction. The repair required: Full diagnostic scan to confirm actuator fault, Removal of turbocharger assembly, Replacement of electronic actuator unit, Recalibration of boost control system, Extended test drive to verify proper operation This was a serious issue requiring immediate attention, as continued driving risks damaging the turbocharger. The symptoms typically worsen over time, leading to complete turbo failure if left unaddressed. The fix restored normal boost pressure, eliminated the whistling noise, and returned fuel economy to standard levels. The engine now maintains stable idle and delivers full power as designed. Would recommend having it checked by a specialist with experience in VAG turbo systems, as accurate diagnosis requires specific diagnostic equipment.

Thanks for sharing your experience. Those symptoms match what Im dealing with on my Q5. After seeing your detailed explanation, Im pretty sure its also the actuator fault in my turbo system causing the boost control issues. Did you remember roughly what the repair cost? Also wondering if youve had any other pressure sensor or wastegate problems since the fix?

Thanks for asking about the follow-up. After getting the boost pressure actuator fault fixed, the car has been running perfectly with no turbo system issues whatsoever. The total repair came to 250 Euro for replacing the electrical bypass valve that was causing the problems. No other pressure sensor or wastegate problems have occurred since then. The repair completely resolved the power loss and strange noises. Looking back, it was definitely worth addressing promptly to prevent any risk of damaging the entire turbo system. The boost control is now working exactly as it should, and fuel consumption has stayed normal ever since the fix. The turbo actuator repair has proven to be a long-term solution, its been over a year now with zero boost-related problems. If your symptoms match what I described, getting that actuator checked should put you on the right path.

After reading these helpful responses, I decided to take my Q5 to a different mechanic who specializes in turbo systems. The diagnosis confirmed my suspicions, it was indeed a faulty actuator causing the boost leak issues. Total repair cost came to 280 Euro, slightly more than expected but still reasonable considering the complexity. The fix took about 4 hours, and they replaced the electronic wastegate actuator along with some related seals. The difference in performance was immediate. No more whistling sounds, power is back to normal, and fuel consumption has dropped back to where it should be. The idle is smooth again too. Been driving it for a few weeks now and everything is working perfectly. The boost pressure is stable and the turbocharger performs exactly as it should. Really glad I got this sorted before any major damage occurred. Definitely worth finding the right specialist for these kinds of turbo-related problems.