BMW i4 Won't Start, Terminal 15 Connection Issue?

Hey there! I've got some experience with EVs, had a similar issue with my 2021 BMW iX3 last summer. I'm what you'd call someone with low experience in car repairs, mostly know the basics. The symptoms you're describing sound exactly like what I faced. My car also wouldn't start and showed multiple error codes. Turned out to be a faulty cable connection to the main control unit. Took it to my regular workshop, and they diagnosed it as a loose connection in one of the main power distribution plugs. The fix cost me 95 Euro, which included the diagnostic and repair work. Before you proceed further, could you share: What error codes are you getting? Did this start happening suddenly or gradually? Any recent work done on the car? This could help narrow down if it's the same issue I had. These electrical gremlins can be tricky in EVs!

Thanks for sharing your experience! My i4 is still relatively new with just 54593 KM on the odometer and had its last service about two months ago. The issue started suddenly yesterday morning, no warning signs before that. I'm getting error code U0100 which points to the lost communication with ECU. Haven't done any recent work except for a software update at the last service. Your input about the loose connection is super helpful, makes me wonder if something got knocked loose during the update. Might take it to the shop tomorrow if I can't figure it out today.

Hey again! Thanks for those details about your i4. when you mentioned the software update, that immediately caught my attention because it's so similar to what happened with my iX3. After hearing about the U0100 code and the timing with your recent software update, I'm even more convinced it could be similar to my situation. In my case, during the software update, they had to disconnect and reconnect several components. What we discovered later was that one of the connectors wasn't properly seated after the update. These modern BMWs are super sensitive to even slightly loose connections, learned that the hard way! Since you've got the same error code I had (U0100), and it started right after service work, I'd bet good money it's connection-related. When my workshop fixed it, they actually found the main power distribution connector was just slightly loose, like, we're talking millimeters here. But that tiny gap was enough to cause all those communication issues. Quick question though, have you checked if your 12V battery is holding charge properly? That's something my mechanic checked first, just to rule it out. It's worth knowing before heading to the shop. Given how new your car is, this should definitely be covered under warranty, especially if it's related to the recent service work. My repair was covered since they admitted it was probably their doing during the update.

Thanks for the detailed follow-up! That's really interesting about your connector issue after the software update. I just checked the 12V battery with a multimeter I had lying around, and it's showing a healthy 12.6V, so that seems fine. You're probably right about the connection being the culprit, especially since our situations are so similar. I made a few calls, and the service center can take a look at it first thing tomorrow morning. They seemed particularly interested when I mentioned the U0100 code and the recent software update. Since my car's under warranty and the issue started after their service, they're being pretty accommodating about getting it checked quickly. Really appreciate you sharing your experience, it's given me a much better idea of what to expect and what to mention to the technicians tomorrow. I'll definitely update the thread once I get it sorted. Thanks again for your help!