BMW 7 Diesel Losing Power with Mysterious Whistling Sound

I had almost identical issues with my 2016 BMW 5 Series diesel last year. The whistling sound and power loss were exactly what I experienced. Turned out the charge air temp sensor wasn't the core problem, it was actually a loose connection in the wiring harness that connects to the sensor. Took my car to the garage and they found the plug was partially disconnected, causing incorrect readings. The sensor itself was fine. They had to remove some engine covers to access it properly, clean the connection points, and secure it back. Not a major repair at all, took about an hour of labor. If you're getting the same symptoms, I'd suggest checking the connections first before replacing any parts. It's really not a serious issue if caught early, but ignoring it could lead to the engine running rich and causing more problems down the line. Just make sure whoever works on it knows BMW electronics well, these sensors are pretty sensitive to improper handling. Good luck with it, Dave

Hey Dave! Thanks for sharing your experience! Really helpful to know it might just be a wiring issue rather than a full sensor replacement. How much did the garage end up charging you for the fix? Also, just curious, has everything been running smoothly since then, or have you had any similar issues pop up?

Just wanted to follow up, yeah, took it to a BMW specialist and you'll be glad to hear it was exactly what I thought, just a dodgy cable connection to the sensor! Only cost me 95 € to sort out, which was a relief as I was worried it might be something more serious. They cleaned up the connection points and properly secured everything back in place. Since then, my car's been running like a dream, no more whistling sounds, full power back, and not a single warning light in sight. It's been about 8 months now and no issues whatsoever. Really worth getting it checked out by someone who knows what they're doing with BMWs. Sometimes these things seem scary but end up being pretty straightforward fixes. Just make sure you don't put it off too long, as I mentioned before, you don't want it causing any bigger problems down the line. Let me know how you get on with yours!

Hey Dave! Thanks a million for all the detailed info! I actually just got back from the mechanic and wanted to update you. You were spot on, it was a simple fix! Found a really good BMW specialist through a and they sorted it right away. Turns out my issue was pretty much identical to yours. The connection was loose and slightly corroded. They cleaned it up, secured everything properly, and the whole thing only took about an hour. Cost me a bit more than yours at 120 €, but still way better than what I was fearing! Car's running perfectly now, no more weird sounds or power issues. The engine light's gone off too. Really glad I didn't go back to my old mechanic who probably would've tried replacing the entire sensor unit. Really appreciate your help on this one. Saved me from a lot of unnecessary stress and expense!