BMW 3 Hybrid Check Engine: ECU Fault and Power Loss Issue

I have some experience with hybrid vehicles. I faced a similar issue with my 2016 BMW 5 Hybrid last year (also happens on regular 5 series). There was a leak in the exhaust system that triggered the check engine light and put the car in limp mode. My workshop found that the exhaust manifold gasket was damaged, causing a leak. The repair took about 4 hours, and I paid around 265 Euro for parts and labor. After the fix, the power and fuel efficiency went back to normal. Before jumping to conclusions about the temp sensor, could you share: Any unusual sounds from the exhaust? Did you notice any burning smell? Have you checked if there's visible damage or rust around the exhaust manifold? Let me know these details, and I might be able to help you narrow down the issue.

Thanks for sharing your experience! My car has 43810 KM and had its last service two months ago. I haven't noticed any burning smells, but there is a slight rattling noise from the exhaust area when accelerating. No visible rust or damage that I can spot, though I might be missing something. The power loss started gradually over the past week before the check engine light came on. Given your similar experience, I'll definitely have the workshop check the exhaust manifold gasket. The symptoms do sound quite similar to what you described. Did you have any warning signs before your car went into limp mode?

Hey there again! Thanks for those additional details about your BMW. You know, when you mentioned that rattling noise during acceleration, it really sounds familiar to what I experienced. In my case, before the car went into full limp mode, I did notice some warning signs. First, there was that same rattling sound you described, it started pretty subtle but got more noticeable over time. I also noticed my fuel consumption creeping up gradually, maybe about 2-3 weeks before the check engine light finally came on. Looking at your mileage (43810 KM), it's actually quite similar to when my issues started (I was around 45000 KM). Given your recent service, I'd be surprised if they missed something major, but these gasket issues can develop pretty quickly. Quick tip from my experience: if you're heading to the workshop, try to record that rattling sound with your phone when accelerating. It really helped my mechanic pinpoint the issue faster. Also, while my repair cost about 265 Euro, prices might have changed since last year, so you might want to get a quote first. Let me know what the workshop says, I'm curious if it turns out to be the same issue. These BMW hybrids are great cars, but they can be a bit tricky when these exhaust system problems pop up.

Thanks so much for all the detailed feedback! That's really helpful, especially about recording the sound, I wouldn't have thought of that. I'll definitely do that before heading to the workshop. It's actually quite reassuring to hear that your symptoms were so similar to mine, and the mileage being close makes me think we're probably dealing with the same issue. I've already called my regular workshop and booked it in for tomorrow morning. They've quoted me slightly higher than what you paid, but at least I now know I'm in the right ballpark price-wise. I really appreciate you taking the time to share your experience, it's put my mind at ease knowing it's likely a known issue with a straightforward fix. I'll probably be back to normal driving by the weekend. Thanks again for all your help! Let me update the group once it's fixed in case anyone else runs into similar problems with their BMW hybrid in the future.