BMW X7 Symptoms: Bad Knock Sensor or Something Worse?

Hey there! I had somewhat similar issues with my 2020 BMW X5 last year. I have some experience working on cars, but nothing too advanced. My symptoms were pretty close to yours, engine light, poor performance, and rough idling. Initially thought it was the knock sensor too, but when I took it to my regular workshop, they found it was actually a loose connection in the wiring harness going to the engine control module. They had to replace some corroded cables and secure the connections properly. The whole thing cost me 95 Euro and fixed all those symptoms. I'd definitely recommend getting it properly diagnosed though, these new BMWs (like your X7 and my X5) can be tricky. Could you share what error codes you're getting from the check engine light? Also, how many miles/kilometers are on your car? This info would help narrow down the possible causes.

Thanks for sharing your experience! My X7 is at 165734 KM and just had its service last month. Got it scanned yesterday and it's throwing the P0325 code. Your wiring harness issue is interesting, definitely something to look into. The symptoms sound really similar, and honestly, I'd be relieved if it turns out to be just a wiring issue rather than the knock sensor itself. Did you notice any improvement in fuel consumption after your repair? I'm currently burning through fuel like crazy!

Oh hey again! Yeah, I totally remember dealing with this on my X5. After they fixed those wiring issues, my fuel consumption improved dramatically, went back to normal within the first tank of fuel. The P0325 code you're getting is interesting because that's exactly what my car was showing too, which is why I initially thought it was the knock sensor. I should mention though, after they fixed the wiring harness on mine, they also found some corrosion on the connector pins going to the knock sensor itself. The mechanic cleaned those up while they were at it. The whole fuel consumption issue was actually quite scary, I was getting about 25-30% worse mileage than usual before the fix. Since your X7's been recently serviced, maybe ask them to specifically check those connections? These BMWs are pretty sensitive to electrical issues, and sometimes even a tiny bit of corrosion can trigger all sorts of weird symptoms. The fact that you're experiencing almost identical issues to what I had makes me think it could be the same problem. Just curious, have you noticed any weird sounds from the engine, especially during acceleration? That might help confirm if it's the same issue I had.

Really appreciate the detailed feedback! Yes, actually I am hearing a slight knocking sound during acceleration, especially when going uphill or pushing the engine a bit harder. That 25-30% extra fuel consumption you mentioned matches exactly what I'm experiencing, it's killing my wallet right now! I'll definitely have them check both the wiring harness and those connector pins you mentioned. It makes total sense that corroded connections could cause these issues, especially since all the symptoms line up so perfectly with what you experienced. I've got an appointment scheduled with my mechanic for tomorrow morning. I'll make sure to have them look specifically at the wiring and connections before jumping straight to replacing the knock sensor. Thanks again for sharing your experience, it's given me a much better direction to explore. I'll update the thread once I get it sorted out!