A6 Diesel Turbo Failure Symptoms & Repair Advice Needed

As an A4 2019 diesel owner, I encountered nearly identical symptoms. The check engine light triggered due to a faulty boost pressure sensor connection at the turbocharger. The whistling sound and power loss were direct results of inconsistent turbo boost readings causing the engine management system to limit performance. The intake manifold pressure readings were fluctuating wildly on the diagnostic scan. The root cause was a damaged wiring harness connection at the turbocharger sensor, which had degraded from engine heat exposure. This created intermittent signal issues, confusing the engine management system. The repair involved replacing the entire sensor wiring harness assembly and recalibrating the turbocharger control system. While not a major mechanical issue, leaving it unaddressed risks damage to the turbocharger and engine from incorrect boost control. The job requires specialized diagnostic equipment to properly test the turbo system and sensor circuits. Would strongly recommend having this checked at a shop specializing in VAG turbo diesel engines, as proper diagnosis is crucial to avoid replacing parts unnecessarily.

Thanks for sharing your experience with the faulty boost sensor. The air intake and turbo system symptoms you described match what I experienced with my A6. Did the repair fix everything completely? Would be helpful to know your repair costs since I want to budget properly. My local shop quoted 850 Euro for diagnostics and repairs but that seems high. Has anything else come up with the turbo system since getting it fixed?

Glad to provide an update on my experience. After having the boost pressure sensor fixed, my car runs perfectly again with zero turbo system issues. The repair was much simpler and cheaper than initially expected, just 95 Euro to fix a damaged cable connection to the sensor. The check engine light disappeared immediately after the repair. The jerky acceleration, whistling sounds, and poor fuel economy were all resolved once the boost sensor was receiving correct readings again. That 850 Euro quote seems excessive considering my repair experience. The problem was just a faulty electrical connection affecting the turbo boost readings, not a mechanical failure. Most issues with boost sensors end up being connector or wiring related rather than the sensor itself failing. Its been over 15000km since the repair with no recurring problems. The turbo system maintains consistent boost now, and fuel consumption returned to normal. Having proper diagnostic equipment to identify the exact issue saved replacing parts unnecessarily.

The mechanics visit went much better than expected. I took my A6 to a different specialist shop after getting feedback here, and they properly diagnosed the issue. Like others mentioned, it was indeed the boost sensor connection causing the turbo problems. The actual repair only took 2 hours and cost 180 Euro total, way less than the 850 Euro quote from my previous mechanic. They found a damaged wire near the turbocharger that was causing incorrect boost readings. After fixing the connection and recalibrating the system, the engine light turned off immediately. The car runs perfectly now, no more jerking or whistling sounds during acceleration. The air intake and turbo boost are working normally again, and fuel consumption is back to where it should be. Really glad I asked here first and avoided unnecessary expensive repairs. Been driving about 2000km since the fix without any issues. The turbocharger performs great and maintains steady boost under all conditions. Definitely learned my lesson about getting a second opinion and finding a shop that actually knows turbo systems.