BMW M4 Boost Issues: Charge Air Sensor Symptoms Explained

Hey! I had a similar issue with my 2016 BMW M3 last year. I'm a car enthusiast with some basic maintenance experience, but I leave the complex stuff to professionals. The symptoms you're describing sound exactly like what I experienced. Mine turned out to be a loose connection at the charge air temp sensor plug, the cable had worked itself loose over time. Took it to my regular workshop, and they diagnosed it pretty quickly. They cleaned the connector, secured it properly, and everything was back to normal. Total bill came to 95 Euro, mostly labor costs. The whistling and reduced power are classic signs of this issue on these turbocharged engines. Before you do anything else, could you share: Current mileage? Any recent maintenance work? Did the problem start suddenly or gradually? Just want to make sure it's the same issue before suggesting anything specific. The M3/M4 platform can be tricky with these sensors.

Thanks for your detailed reply! My M4 has 162369 KM on the clock and had its last service about 3 months ago. The issue actually started gradually over the past week, getting worse each day. Started with just the whistling sound, then the power reduction kicked in, and finally the check engine light popped up yesterday. Haven't had any other work done recently besides regular maintenance. Really appreciate the insight about the loose connection, that's definitely something I'll have checked out first since it seems like a simple fix that could save me some headache.

Hey again! Back to share more about my experience since we're dealing with similar issues. After hearing about your mileage and how the problem developed gradually, it reminds me even more of what happened with my M3. The way your symptoms progressed, starting with the whistle, then power loss, and finally the CEL, that's exactly how mine played out too. Mine had about 155000 KM when it happened, so pretty close to yours. When I first replied, I thought it might just be the loose connection like in my case, but given how gradually it developed for you, there might be more to it. After my initial fix, I actually had the issue come back a few months later. Turned out the sensor itself was starting to fail, not just the connection. The workshop explained that these sensors often degrade over time, especially at our kind of mileage. The second time around, I had them replace the entire sensor unit. Cost more than just fixing the connection (around 280 Euro total), but it's been perfect for the past year. Might be worth having them check both the connection AND the sensor condition while they're at it. These S55 engines are pretty sensitive to sensor readings, so it's better to be thorough. Let me know what you find out when you get it checked!

Thanks so much for the follow-up info! That's super helpful to know about the potential sensor failure, especially since our cars have similar mileage. I've actually just booked an appointment with my workshop for tomorrow morning. I'll definitely have them check both the connection and the sensor itself, don't want to risk having to go back twice like you did! Really appreciate you sharing your full experience. The cost doesn't sound too bad either, especially if it sorts out the problem for good. Even though 280 Euro isn't cheap, it's way better than some of the repair bills these M cars can rack up. I'll update you once I get the diagnosis and repair done. Thanks again for all the detailed advice, definitely feeling more confident about handling this now!