BMW M3 Voltage Issues: Electrical Gremlins Strike Again

Hey there! I have some experience working on cars, and this sounds really familiar. Had a similar nightmare with my '03 BMW M5 last winter (also had an '04 335i before). Dealt with the exact same symptoms, weak starts, error messages going crazy, and all sorts of electrical weirdness. Turned out my battery was on its last legs and wasn't holding charge properly. Took it to my regular workshop, and they confirmed the battery was toast after running diagnostics. Got it replaced and all those gremlins disappeared instantly. Including parts and labor, it set me back about 290 Euro, but totally worth it for peace of mind. Before jumping to conclusions though, could you share some more details? Like how old is your current battery? Are you getting any specific error codes? What kind of driving do you usually do (short trips vs longer drives)? This info would help nail down if you're facing the same issue I had.

Thanks for sharing that experience! Yes, my situation does sound pretty similar. I've got 44757 KM on the clock and had my last service about 3 months ago. The battery is actually original (I know, I know, I should've replaced it ages ago), and the symptoms really started getting bad after some short trips around town. I'll definitely get it checked out by my mechanic, your battery diagnosis makes a lot of sense given what I'm experiencing. The weak starts are particularly noticeable in the morning, and the error messages seem to pop up more during those shorter drives. Really appreciate you taking the time to share your story. Seems like I might be looking at a similar fix. At least it's not as scary (or expensive) as I initially thought!

Hey again! Glad my previous response helped you out. After reading about your original battery still being in there, I'm even more convinced we had the same issue. Actually, this reminds me, I forgot to mention in my first reply that before I changed my battery, I also noticed the errors would get especially bad during short trips, just like you're experiencing. With my M5, I learned the hard way that these performance BMWs are pretty demanding on their electrical systems. When I discovered my battery was original too, my mechanic actually laughed and said I was lucky it lasted that long! Quick thing I wanted to add from my experience, after the battery replacement, make sure they register/code the new battery to the car. I initially didn't know this was necessary, but these BMWs need to be told they've got a new battery to optimize charging. When I first replaced mine, they forgot to do this step and some minor issues lingered until we got that sorted. Let us know how it goes after you get it checked out. Betting you'll see all those gremlins disappear just like I did!

Thanks everyone for the great advice! You all really helped calm my nerves about this whole situation. Just got back from my mechanic and wanted to give a quick update, turns out you were absolutely spot on! The original battery was indeed the culprit. My mechanic couldn't believe I was still running on the factory battery after all this time. They replaced it with a new one, made sure to code it properly to the car (thanks for that tip about battery registration, would've never known about that!), and like magic, all those error messages disappeared. Total cost came to around 300 for everything, parts and labor included. Such a relief it wasn't something more serious. The car starts up strong now, and all those electrical gremlins are gone. Funny how something as simple as an aging battery can cause so many weird issues. Really appreciate everyone taking the time to share their experiences. Made the whole situation way less stressful knowing others had dealt with the same thing. Lesson learned about not waiting so long to replace the battery next time!