BMW 3 Hybrid Won't Start: Terminal 15 Power Issue

Hey there! I had a similar issue with my 2020 BMW 5 Series Hybrid (I also own a BMW 7). I have some experience working on cars, but electrical issues are tricky. Last month, my car wouldn't start and had similar symptoms. After taking it to my trusted workshop, they found a faulty cable connection to the ECU. The mechanic discovered some corroded terminals that were interrupting the power supply. The fix wasn't too complex, they replaced the damaged cables and cleaned the connections. Cost me 95 Euro and the car's been running perfectly since. What's your exact model and mileage? This could help pinpoint if it's the same issue I faced. These problems can sometimes be model-specific, so more details would help me share relevant info.

Thanks for sharing your experience! My 3 Series just hit 16353 KM and had its latest service about two months ago. Everything was fine until this morning. Your electrical issue sounds pretty similar to what I'm experiencing. Good to know it might just be a cable connection problem, that's somewhat reassuring compared to what I was imagining! I'm planning to get it checked tomorrow. Did your BMW throw any specific error codes when you had this problem? Just wondering if I should look out for anything particular when I take it to the shop.

Hey again! Yes, when my 5 Series had this issue, I remember getting error code P0685, which specifically relates to ECU power supply problems. The symptoms were identical, no start, no ECU voltage. Interesting that yours happened right after hitting 16K, mine was around 18K when it occurred. Since you mentioned it was fine after the service two months ago, I'd definitely have them check if any of the work they did might have inadvertently affected the connections. Sometimes these issues can develop gradually after maintenance if something wasn't properly secured. One thing I forgot to mention in my first response, before taking it to the workshop, I actually tried checking the fuse box myself (since I do basic maintenance), but everything looked fine. It turned out the problem was deeper in the wiring harness. The corroded terminals weren't visible without removing some panels. The repair really wasn't as scary as I initially thought. They had my car back to me the same day. Just make sure they thoroughly check all the connections, not just the obvious ones. When you take it in tomorrow, mention the Terminal 15 suspicion, it'll give them a good starting point, though in my case it turned out to be those corroded cables instead. Let me know how it goes! Always happy to compare notes with another BMW hybrid owner.

Thanks so much for all the detailed information! Really appreciate you mentioning that error code P0685, I'll definitely bring that up when I take it in. It's super helpful to know about the hidden wiring harness issue too, since I was actually thinking about checking the fuse box myself tonight. I'll leave it to the professionals instead! You're right about the timing being interesting, maybe there's some connection to the recent service. I'll make sure to ask them to check if anything could have come loose during the maintenance. Pretty relieved to hear your repair was quick and straightforward. Really grateful for you sharing your experience, it's given me a much better idea of what to expect tomorrow. I'll update you once I get it sorted. Thanks again for taking the time to help out a fellow BMW owner!