BMW i3 Hybrid Problems: Knock Sensor or Something Else?

Hey there! I have some experience working on hybrid vehicles. Had a similar issue with my 2020 BMW i4 last year. I initially thought it was something major, but it turned out to be just a faulty connection to the knock sensor, exactly what you're suspecting. Took it to my workshop, and they diagnosed a loose wiring harness connection to the sensor. The whole repair, including diagnostics, cost me 95 Euro. Since then, my car's been running smoothly, no more sluggish acceleration or fuel efficiency issues. But before jumping to conclusions, could you share: Any error codes you're getting? When did these symptoms first appear? Have you noticed any unusual sounds when accelerating? Knowing these details would help confirm if your issue matches what I experienced with my i4. These BMWs can be tricky sometimes!

Thanks for your detailed response! Mine has 31533 KM on the clock and just had its service last month. The symptoms actually started about a week ago. I'm getting error code P0325, and there's a slight knocking sound when I accelerate, especially between 2000-3000 RPM. The sound wasn't there before. The fuel consumption has gone up quite noticeably too, I used to get much better efficiency from the hybrid system. Think I'll get it checked out by a professional just to be safe. The symptoms do sound very similar to what you experienced with your i4.

Hey again! Thanks for providing those details. Your situation sounds exactly like what I dealt with on my i4! That P0325 code is definitely knock sensor related, it's the same one I got. And that knocking sound between 2000-3000 RPM? Yep, had that too. It's almost like déjà vu hearing your description. When I took mine in, they first checked the wiring harness connection like I mentioned before. But here's something I didn't say in my first reply, they also found some corrosion on the sensor's electrical contacts. The technician cleaned those up and applied some dielectric grease to prevent future issues. The total repair time was only about an hour, and my fuel efficiency went right back to normal. The knocking sound disappeared completely too. These i-series hybrids are pretty sensitive to knock sensor issues, they tend to run super conservative programming when they detect any potential problems, which explains the poor performance you're seeing. Since you just had service done, maybe check if this could be covered under warranty? Either way, it's usually a pretty straightforward fix. Keep me posted on what you find out, I'm curious if your issue turns out to be identical to mine!

Thanks so much for all this information! Just got back from the workshop and you were spot on, it was indeed the knock sensor issue. They found both a loose connection and some corrosion, just like in your case. They cleaned it up, secured everything properly, and applied that dielectric grease you mentioned. The whole repair took about an hour and cost roughly the same as yours. They couldn't cover it under warranty since it was apparently caused by some water intrusion, but I'm just glad it wasn't anything more serious. Car's running beautifully now, no more knocking sound, the acceleration is back to normal, and the hybrid system is working efficiently again. Really appreciate you sharing your experience, it helped me feel much more confident about what I was dealing with. These BMWs sure can be finicky sometimes, but at least this was a relatively simple fix!