BMW 1 Series ECU Power Loss, Terminal 15 Issue

Hi there! I've had some experience working on cars, mainly basic maintenance and electrical issues. I faced a very similar problem with my 2016 BMW 2 Series diesel last year. The symptoms were identical, no ECU power and starting issues. Turned out it was a faulty wiring connection near the ECU plug. Took it to my trusted workshop, and they traced it to a corroded connector that wasn't making proper contact. The fix wasn't too complicated, they had to clean the connection points and replace a damaged cable section. Whole thing cost me 95 Euro, and the car's been running perfectly since then. Before I can provide more specific advice, could you share: Have you noticed any warning lights before this happened? Does your battery show good voltage? Any recent work done on the electrical system?

Thanks for your detailed response. My car has done 124476 KM and had its last service just two months back. I did notice the battery warning light flickering a couple of times last week, but it went away on its own. Haven't done any electrical work recently, but I'll definitely check the battery voltage as you suggested. Just worried it might be something more serious since it's completely dead now. Hoping it's just a connection issue like yours was.

Hey again! Good to hear back from you. That flickering battery warning light you mentioned is definitely a red flag, reminds me exactly of what happened with my BMW before things went south. In my case, the flickering was actually the first sign of the failing connection, not a battery issue as I initially thought. Since your car has similar mileage to what mine had (mine was at about 130,000 KM when this happened), and you're seeing identical symptoms, I'm even more convinced it could be the same problem. The corrosion on my connector had built up gradually over time, and the warning light started flickering about a week before the car finally refused to start. Quick tip from my experience: make sure they check all the ground connections too. My mechanic found that while the main issue was the corroded connector, there was also some minor corrosion on one of the ground points that could've caused problems down the line. Have you managed to check the battery voltage yet? Even though I don't think it's your main problem (given how similar this is to what I experienced), it's still worth checking to rule it out. Let me know what you find, I'm quite curious to know if this turns out to be the same issue as mine.

Thanks so much for sharing your experience and the detailed explanation! I actually just checked the battery voltage, it's showing 12.1V, which seems a bit low but not terrible. Your story about the corroded connector makes a lot of sense, especially since our cars have similar mileage and symptoms. I've booked it in at the workshop for tomorrow morning, and I'll definitely mention checking the ground connections too, that's a really helpful tip I wouldn't have thought about. The fact that your repair was relatively straightforward and didn't break the bank is really reassuring. I was worried I'd be looking at a massive ECU replacement or something similar. Will let you know how it turns out once the workshop has taken a look. Really appreciate you taking the time to help me troubleshoot this!