SQ7 TDI Turbo Whistling Points to Boost Sensor Failure

Had similar symptoms on my 2017 Q7 3.0 TDI. The turbocharger system issues started exactly the same way, whistling noise, power loss, and the check engine light. Initial diagnosis pointed to the boost sensor, but it turned out the wiring harness connecting to the sensor was damaged. The cable connection had deteriorated due to engine heat exposure, causing intermittent signal failures in the turbo boost control. This made the engine computer receive incorrect boost pressure readings, leading to poor performance and excessive fuel consumption. The fix required replacing the entire wiring harness for the boost sensor and recalibrating the turbo system. While not the most expensive repair, getting proper diagnosis was crucial since misdiagnosing it as just a faulty sensor would not have solved the root cause. This is a known weak point in these engines. The symptoms point strongly to either the boost sensor itself or its wiring connection. Get it checked soon, as running with incorrect boost pressure can potentially cause more serious turbocharger damage.

Thanks for sharing that experience. The wiring harness issue sounds exactly like what I am experiencing with the air intake and boost sensor readings. My SQ7 is showing all those same symptoms, the power loss and whistling are particularly concerning. Did you remember roughly what it cost to fix? The part about potential turbo damage has me worried, so I want to budget accordingly. Also curious if you have had any other pressure sensor or intake manifold issues since the repair was done?

Thanks for asking about the follow-up. The issue was completely resolved after fixing the boost pressure sensor connection. It ended up being a straightforward repair, just 95 Euro to fix the faulty cable connection to the sensor. The engine light cleared immediately after the repair, and the turbo system has been working perfectly since then. No more whistling sounds or power loss issues. Most importantly, fuel consumption returned to normal levels once the boost pressure readings were accurate again. Have not experienced any other turbocharger or sensor problems in the 18 months since the repair. The key was catching it early before the incorrect boost pressure could cause any lasting damage to other components. Would definitely recommend getting yours checked soon to avoid any potential complications. While my repair was relatively inexpensive since it was just the wiring, catching these issues early typically prevents more costly turbo system repairs down the line.

I took my car to a new mechanic yesterday after reading these responses. Turns out it was exactly what was described, a damaged wiring harness affecting the boost sensor readings. The check engine light and all symptoms matched perfectly. The repair was quick and reasonable at 120 Euro for parts and labor. The mechanic showed me how the intake manifold pressure readings were way off due to the faulty connection. After replacing the wiring harness and recalibrating the system, the engine performance returned to normal immediately. No more whistling sounds during acceleration and the power is back to what it should be. Fuel consumption has already improved significantly. Really glad I got this sorted before any serious damage occurred to the turbo system. The mechanic did a thorough job and even showed me what to watch for in the future.