BMW 1 Series ECU Issues: Power Loss and System Failures

Hey there! I have some experience working on cars, and I actually faced something very similar with my 2010 BMW 3 Series (also had a 5 Series before). Those symptoms sound exactly like what I dealt with, slow starts, power issues, and unusual electrical glitches. After some headaches, it turned out to be a faulty main relay. Got it fixed at my workshop for about 120 Euro, and it's been running perfectly since then. Before jumping to conclusions about the ECU though, could you share: What error codes are you getting? Does it happen more when the engine is cold or warm? Have you noticed any other electrical issues? This info would help verify if you're dealing with the same problem I had.

Thanks for sharing your experience! My symptoms do sound pretty similar to what you described. I've got 45887 KM on the clock now and just had a service last month, but these issues started popping up recently. The error codes I'm getting are mainly related to power supply interruptions. It definitely happens more when the engine is cold, especially in the morning. And yes, I've noticed the power windows and radio occasionally glitch out too. Given what you've mentioned about the main relay, that could definitely be it. Much rather it be that than a full ECU replacement! I'll get it checked out and keep you posted on what they find. Really appreciate the help!

Hey again! Wow, after reading your latest update, I'm even more convinced we had the same issue. The symptoms match perfectly, especially those power supply interruption codes and the cold start problems. My BMW had almost the same mileage too when this started happening. You know what's funny? I also initially freaked out thinking it was the ECU, but the relay was such a simpler fix. When my power windows started acting up, that was the big clue. The main relay affects so many systems because it controls the power distribution. Just to add to my previous advice, when my mechanic replaced the relay, he also checked the battery connections since they can cause similar symptoms. Turned out they were a bit corroded, so he cleaned those up too. The whole job took less than an hour. Keep us updated on what your mechanic finds! I've got a good feeling it'll be something straightforward like the relay. Would be great to hear if my experience helped point you in the right direction.

Thanks so much for all this detailed feedback! It's really reassuring to hear your story, especially since the symptoms match up so closely. The tip about checking the battery connections is super helpful too, I actually noticed some white crusty stuff around the terminals recently but didn't think much of it. I've booked the car in for tomorrow morning, and I'll definitely ask them to check the main relay and battery connections first. You've saved me a lot of worry about a potential ECU replacement, which would've been way more expensive and complicated. I'll definitely post an update once I get the diagnosis. Really grateful for the help and detailed explanations. It's great to find someone who's been through the same thing and can share their experience. Thanks again for taking the time to help out!