BMW M2 Won't Start: ECU Power Loss & Terminal 15 Issue

Hey there! I had a similar issue with my 2016 M4 (some experience with basic maintenance and repairs). The symptoms were exactly the same, no start, ECU power issues. Turned out to be a faulty connection in the wiring harness near the ignition switch. Took it to my regular workshop last year, and they diagnosed it pretty quickly. They had to replace some corroded connectors and re-pin a few cables. The whole thing cost me 95 Euro and fixed the problem completely. Could you share more details about your M2? Like when did this start happening? Any recent work done on the car? Or did it just suddenly occur? This could help pinpoint if it's the same issue I had. Also, does your battery check out okay? That's always a good first thing to verify with these symptoms.

Hey! Thanks for sharing your experience. Mine's at 68517 KM and just had its service done 2 months ago. The issue started completely out of nowhere last week. No recent work besides regular maintenance. Already checked the battery, it's showing 12.6V and was replaced last year, so that should be fine. I was thinking it might be something similar to what you experienced with the wiring harness since these symptoms match up pretty well. I'll probably have my mechanic take a closer look at those connections you mentioned. The timing seems a bit odd though, since it was running perfectly fine and then just stopped working suddenly. Did you notice any warning signs before your car completely failed to start? Been trying to think back if I missed any indicators.

Hey again! Yeah, your situation does sound really similar to what I went through. You know, it's funny you ask about warning signs, in my M4, it also happened pretty suddenly, just like yours. One day it was running perfectly fine, and the next... nothing. After my mechanic dug deeper into my case, turns out there was some sneaky corrosion building up in those connectors that wasn't visible from the outside. The service technician mentioned that these issues can develop silently and then just suddenly show up, especially in these models. The fact that yours also happened suddenly after running fine makes me think even more that it could be the same problem. The good news is, if it is the same issue, it's totally fixable. Just make sure your mechanic checks those ignition switch connections thoroughly. In my case, they initially thought it might be something more complex with the ECU itself, which would've been way more expensive. But it turned out to be just those corroded connections near the ignition switch. Also, your battery voltage sounds good, same as mine was when I had the issue. I'd still get them to check the ground connections though, just to be thorough. These cars can be pretty sensitive to even minor electrical issues. Let me know what they find, I'm really curious if it turns out to be the same problem!

Thanks so much for all that detail! That's really helpful to know about the hidden corrosion, definitely makes me feel better about not spotting any warning signs. I've just booked it in with my mechanic for tomorrow morning. I'll make sure to mention the ignition switch connections and ground points specifically. Really hoping it turns out to be something similar to your case and not a full ECU replacement, my wallet would definitely appreciate that! You're right about these cars being sensitive to electrical issues. It's kind of crazy how something as small as corroded connectors can completely shut down such a sophisticated car. But I guess that's modern vehicles for you. I'll definitely update you once I get it sorted. Thanks again for taking the time to share your experience, it's been super helpful in narrowing down what to look for!