BMW i7 Sudden Power Loss Mystery, High Voltage Issues

I faced a similar issue with my BMW i4 2019. The sudden power loss and shutdown happened to me three times before I got it properly diagnosed. At the garage, they found that the main battery management system had a critical fault, which was causing incorrect readings and forcing emergency shutdowns to protect the powertrain. The high-voltage system errors were actually a symptom, not the root cause. The fix required reprogramming the battery management module and replacing two faulty cell sensors. It was quite serious since it affected the entire high-voltage system. The car was in the shop for four days while they verified everything was working correctly after the repair. If you're getting the same symptoms, I'd strongly suggest going directly to a BMW certified service center that specializes in their electric vehicles. Regular mechanics often lack the specific diagnostic tools needed for the i-series electrical systems. This isn't something you want to leave unaddressed, as it can potentially leave you stranded or create more serious issues with the battery pack.

Hey, thanks for sharing your experience with the battery management system issue. Really helps to know I'm not alone with these problems! That sounds like exactly what I'm experiencing. Did you remember roughly how much the whole repair set you back? Also, just curious, have you had any other electrical gremlins pop up since they fixed it? Would love to know if this was a one-time thing or if I should be watching out for anything else.

Hey there! Just wanted to update you since you asked about the costs. My repair bill came to 290 € to fix that battery issue, which wasn't as bad as I initially feared. The great news is that since getting it sorted at the specialist, I haven't seen that high-voltage error message even once, the car's been running perfectly! And to answer your other question, nope, haven't had any other electrical quirks show up since then. It really does seem like it was just that one isolated issue with the battery management system. Once they got that sorted out, everything's been smooth sailing. The car feels as good as new now, maybe even better since they also updated some of the system software during the repair. I reckon you'll have the same experience once you get yours fixed. Just make sure you're taking it to someone who really knows their stuff with these electric BMWs. Regular mechanics might charge less, but these high-tech systems need proper diagnostic equipment and expertise.

Thanks for the detailed follow-up about the repair costs and long-term experience! Finally got my i7 checked out at the certified BMW service center yesterday. what a difference compared to my first mechanic visit! They spotted the battery management system fault right away with their diagnostic tools. The technician showed me the faulty sensors and explained everything clearly. Got it all fixed up, similar cost to what you paid, actually. Took the car for a proper test drive today and no more shutdowns or error messages! Such a relief to have this sorted. Really appreciate your help pointing me in the right direction. Definitely the right call going to the specialist, worth every penny to have it done properly rather than messing around with mechanics who don't know these electric systems. Just hope others with similar issues find this info useful too!

Hi! I have a 2016 bmw 330e f30 and my Carly showed error code 21A123. I have no issues with the car at the moment. I have no idea what this code is about. Should I be worried?

Error code 21A123 typically relates to the high-voltage battery management system in BMW plug-in hybrids. Even if you're not experiencing any issues right now, it's important to address this code to prevent potential problems. I recommend having a certified BMW service center inspect your vehicle. They can perform a detailed diagnostic to determine if there's an underlying issue that needs attention. Let me know how it goes or if you have any further questions!