BMW X4 Start-Stop Malfunction Leads to Random Engine Dies

Hey there! I have some experience working on cars and had a very similar issue with my 2021 BMW X3 last year. The symptoms you're describing are almost identical to what I experienced, unusual shutoffs, start-stop malfunction, and warning lights. In my case, it turned out to be a severely discharged battery that was on its last legs. My trusted mechanic ran a thorough diagnostic and found the battery was barely holding a charge. Had it replaced for about 290 Euro, and all those issues disappeared completely. The X5 parked next to mine at the workshop had similar symptoms too. Before you head to a mechanic though, could you share: How old is your current battery? Are you noticing any slow cranking when starting? Have you had any other electrical issues lately? This info would help confirm if you're dealing with the same problem I had.

Thanks for sharing your experience! I'm having the exact same symptoms with my X4 (currently at 133659 KM). Had my latest service just two months ago, but didn't have them check the battery specifically. The battery is actually the original one from when I got the car, and now that you mention it, I've noticed the engine's been cranking a bit slower lately, especially in the morning. Haven't spotted any other electrical issues though. Your suggestion about the battery makes a lot of sense, I'll definitely get it checked out. Thanks for giving me a starting point to look into! Fingers crossed it's just the battery and not something more complicated.

Hey again! Glad I could help point you in the right direction. After reading your reply, I'm even more convinced it's the battery, especially since you mentioned the slow cranking in the morning. That's exactly how mine started acting up too! The original battery lasting this long is actually pretty impressive. Mine died at around 120,000 KM, so yours has already outlived mine by quite a bit. These start-stop systems are really demanding on batteries, and once they start to wear down, you get all those weird symptoms we discussed. Quick tip from my experience, when you get it replaced, make sure they use an AGM battery that's specifically compatible with the start-stop system. I made the mistake of trying to save money with a regular battery first, and guess what? The problems came right back after a few weeks. Had to swap it out for the proper one anyway. Let me know how it goes after you get it checked out. I'd bet good money that's your issue right there.

Thanks so much for all the detailed advice! That's really helpful about making sure to get an AGM battery, definitely don't want to waste money on the wrong type and have to replace it twice. I've actually just called my mechanic and booked it in for tomorrow morning. You're right that my battery has done well to last this long, but sounds like it's finally giving up. I'll make sure to specifically ask about the AGM battery compatible with start-stop systems. Really appreciate you taking the time to share your experience, it's saved me a lot of worry thinking it might be something major. I'll update the thread once I get it sorted, in case anyone else runs into the same issue with their X4. Thanks again for your help!