Audi Q7 Turbo Issues: Stalling, Power Loss & Bad MPG

Had identical symptoms on my 2015 Audi A6 3.0 TDI. The turbocharger was fine, but the boost pressure sensor wiring harness had deteriorated. The check engine light pattern matched exactly what you describe. The main symptoms were: Unusual stalling, Boost leak sounds, Poor acceleration, High fuel usage, Turbo boost inconsistency After inspection, it turned out the wiring connector at the intake manifold sensor was corroded and making poor contact. The sensor itself was working correctly, but the compromised connection caused erratic readings, making the engine computer reduce power. This was not a major repair, just required cleaning the connections and replacing the wiring harness section. The turbocharger and other core components were intact. The fix restored normal operation and resolved all symptoms. This is a common issue on VAG diesel engines from that generation. Would recommend having the wiring connections checked before assuming more serious turbo system problems.

Thanks for the detailed reply about the wiring harness issue. Sounds exactly like what I am experiencing with the boost sensor readings going crazy. Did you happen to remember the repair cost for this fix? Also curious if any other issues popped up with the turbo system after getting the wiring sorted? Want to be prepared in case the pressure sensor readings are masking other problems.

Can confirm the fix worked perfectly, took my car to the shop last week for this exact boost sensor problem. Total cost was 95 Euro for repairing the faulty cable connection to the sensor. The check engine light disappeared immediately and haven't had any issues since. The turbo system is running smoothly now with no unusual sounds or performance problems. Fuel consumption returned to normal and the power delivery is consistent again. No other boost-related problems have surfaced after the repair. The mechanic showed me that the air intake readings were completely stable once the connection was fixed. This proves it was just the wiring causing those erratic boost sensor signals, not a deeper issue with the turbocharger itself. Worth mentioning that the repair was quick, took them under an hour to trace and fix the connection. Much better than having to replace major components of the turbo system.

Thanks for the input. Just got back from the mechanic and wanted to share my experience. They found the corroded wiring connection near the boost pressure sensor, exactly as suggested here. The repair was straightforward, cleaned up the contacts and replaced a small section of the harness. Total cost came to 120 Euro for parts and labor. The check engine light cleared right up and the turbo system is working perfectly now. No more weird noises or performance issues. Fuel economy is back to normal and the car pulls strong again without any hesitation. Really glad I checked here first instead of jumping to conclusions about major turbo problems. Saved me from potentially spending way more than necessary. The whole repair took less than 2 hours and fixed all the symptoms completely.