Audi S5 Turbo Issues: Boost Loss and Engine Warning

Had the exact same symptoms on my 2020 Audi A5 diesel. The check engine light and turbo issues were caused by a faulty boost sensor connection. After thorough diagnostics, it turned out the wiring harness to the boost sensor had partially corroded, causing intermittent signal problems. The symptoms match perfectly, reduced power, poor fuel economy, and that characteristic whistling noise from the air intake system. The turbocharger itself was fine, but the engine management system was getting incorrect boost readings, causing the erratic behavior. This is generally not a critical repair if addressed promptly, but ignoring it can lead to engine performance issues and potential turbocharger damage over time. The repair involved replacing the wiring harness and boost sensor assembly. Once fixed, the engine light cleared and normal power was restored. For these specific turbocharger system issues, its crucial to get proper diagnostics with specialized equipment that can read boost pressure values. The engine light codes alone dont tell the whole story.

Thanks for sharing your experience! This matches what happened with my S5 exactly. After getting the boost sensor and wiring harness replaced, the turbocharger performance went back to normal and the whistling noise completely disappeared. Would you mind sharing what the repair cost came to for you? Curious if similar to what I paid. Also, has the air intake system given you any other issues since the fix? I had to get my pressure sensor cleaned a few months later because of a small boost leak, but its been running perfectly after that.

Thanks for asking about the repair costs. After seeing my mechanic, the bad boost sensor issue was completely resolved. The fix was straightforward, just needed to repair a faulty cable connection to the boost sensor, which came to 95 Euro total. The intake manifold and entire turbo system have been working flawlessly since the repair. No boost leaks or check engine lights in the past year. The turbocharger is delivering proper boost pressure now, and fuel consumption returned to normal levels. I did regular maintenance checks of the air intake system afterward, but havent needed any additional repairs. The original problem was purely electrical, just that loose connection throwing off the boost sensor readings. Once fixed, all the performance issues and strange noises disappeared completely.

Perfect update from my experience! I got it fixed last month at a specialist turbo shop, not the dealer. Total bill came to 450 Euro for the boost sensor, wiring harness, and labor. Bit pricey but worth every cent since the turbocharger is working perfectly now. Had to wait a few days for parts but the actual repair only took about 3 hours. The check engine light cleared right away and that annoying whistling from the air intake completely disappeared. Fuel consumption dropped back to normal and the power feels great again. Only extra thing I needed was a pressure sensor cleaning last week due to a small boost leak, cost me another 85 Euro. But since then, no issues at all. The shop did a great job explaining everything and even showed me the corroded wiring that was causing all the trouble. Really glad I got this sorted before any serious damage happened to the turbocharger system. Next time I notice any boost issues, I wont wait around, heading straight to the specialist.