BMW 6 Diesel: Boost Issues & Temperature Sensor Warning

Hey there! I've got some experience with BMWs, though I'm no expert. Had a similar issue with my 2017 BMW 5 diesel last year, and I've also owned a BMW 3 series before. That whistling noise and power loss sounds exactly like what I experienced. In my case, it turned out to be a loose connection to the charge air temp sensor. My mechanic found that the wiring harness was slightly damaged, causing intermittent connection issues. The fix was pretty straightforward, they replaced the connector and secured the wiring properly. Cost me about 95 Euro and fixed the problem completely. Could you share what engine variant you have and if you notice any other symptoms? Also, does the whistling get louder at higher RPMs? This info would help me confirm if it's the same issue I had.

Thanks for sharing your experience! I've got the 3.0L diesel, and yes, the whistling definitely gets more noticeable at higher RPMs. Last service was done just 3 months ago at 172869 KM, and everything was fine until this started happening last week. It's good to hear your fix was relatively simple and inexpensive. No other symptoms besides what I mentioned, just the power loss and that annoying whistle. Were there any warning signs before your sensor started acting up? I'm hoping it's just a wiring issue like yours and not something more serious with the turbo.

Oh, glad to help further! Yeah, my 2017 530d had the exact same symptoms. Actually, thinking back, I did notice a slight hesitation in acceleration maybe a week before the main issues started, but I brushed it off at the time. Big mistake on my part! The weird thing with mine was that the problem would sometimes seem to fix itself for a few hours, then come back worse than before. That's what made my mechanic suspect the wiring rather than the sensor itself. When they dug deeper, they found that the connector had some corrosion too, probably from moisture getting in there. Since you mentioned your car's mileage, mine was around 165,000 km when this happened. These BMWs are pretty solid, but those sensors and connections can get finicky with age and miles. After they fixed mine, I haven't had any issues for over a year now. Just one heads up, make sure they check the wiring all the way back to the main harness. My first mechanic only replaced the sensor, and the problem came back after two days. Had to go to another shop that actually traced the whole circuit. Saved me from buying unnecessary parts. Keep us posted on what they find! I'm curious if it turns out to be the same issue.

Thanks so much for all the detailed info! That's really helpful, especially about the wiring harness check. I've just booked it in for tomorrow morning, and I'll definitely mention your experience to the mechanic. It's actually reassuring to hear that yours had similar symptoms at about the same mileage. The intermittent nature of your problem is interesting, I've noticed mine seems a bit better in the morning when it's cool, which might fit with your wiring theory. Really appreciate you sharing about that first mechanic too, could save me from going through the same hassle. I'll make sure they do a thorough check of the whole circuit instead of just swapping out the sensor. Will definitely update the thread once I know what's going on. Thanks again for taking the time to share your experience, it's made me feel a lot better about the whole situation!