BMW i3 Hybrid Dead: Terminal 15 Power Loss Issue?

Hey there! I have some experience working on hybrid vehicles and faced a really similar issue with my 2014 BMW i8 (my second BMW after the X5). I had exactly the same symptoms, no start, error code, and power delivery issues. Turned out to be a faulty cable connection to the ECU. Took it to my regular workshop and they diagnosed it pretty quickly. They had to replace some corroded connectors and re-establish proper connections. The whole thing cost me 95 Euro and the car's been running perfectly since then. Before I share more specific details about my experience, could you share: Have you checked if your battery terminals are clean and properly connected? Are you getting any specific error codes? Did this start happening suddenly or gradually? Let me know these details and I can probably help you narrow down if it's the same issue I dealt with.

Thanks for your detailed response! I've got almost the exact same symptoms with my i3 (103434 KM on the clock, last serviced 3 months ago). Really helpful to know about the corroded connectors, that could definitely be it. I checked the battery terminals yesterday and they look clean, but maybe there's corrosion I can't see. The error code I'm getting is P1542, and it all started pretty suddenly last weekend. Just went to start the car and... nothing. Good to hear your fix was relatively straightforward and not too expensive. Think I'll get it checked out at the shop this week. Did your mechanic mention how long the repair typically takes?

Hey again! Yeah, that P1542 code does sound very similar to what I experienced with my i8. My car had about 98000 KM when this happened, and it was also a sudden failure, just wouldn't start one morning. The repair itself didn't take too long actually, my mechanic had it sorted in about 2-3 hours. Most of that time was spent on proper diagnosis and accessing the connectors, which are a bit tricky to get to in these hybrids. The actual replacement of the corroded parts was pretty quick. Just a heads up though, while my issue was solved with just replacing the connectors, sometimes these symptoms can also point to a failing voltage regulator. My mechanic initially thought that might be the case with mine, but luckily it wasn't. If it is the regulator, it might take a bit longer and cost more. I'd definitely get it checked out sooner rather than later. In my case, putting it off could have led to more damage to the ECU, which would have been way more expensive to fix. Keep me posted on what they find, really curious to know if it's the same issue I had!

Thanks so much for all that info! That's really reassuring about the repair time, 2-3 hours isn't bad at all. I've just called my regular mechanic and they can fit me in tomorrow morning. Pretty concerned about that voltage regulator possibility you mentioned though, fingers crossed it's just the connectors like in your case! Being stuck without my car is such a pain, but you're absolutely right about getting it sorted quickly. Don't want to risk any damage to the ECU. I'll definitely update you once I know what's actually wrong with it. Really appreciate you taking the time to share your experience, it's been super helpful having someone who's dealt with the same issue! I'll post back here tomorrow after the mechanic has taken a look.