BMW Z3 Battery Issues Causing Multiple System Failures

I had very similar issues with my 2005 BMW Z4 last winter. After several attempts to start the car, I got those same warning lights and system failures. The voltage test at the garage showed the battery was severely discharged and couldn't hold a proper charge anymore. Turned out my alternator was actually fine, but the original battery had completely died. They did a full electrical system check to rule out any parasitic draws. It was a straightforward fix, just needed a new battery with the correct specs and proper battery registration to the car's computer system. This is actually a common issue with BMWs of this age. The original batteries typically last 5-7 years, and when they start failing, they can trigger multiple system warnings. It's not a major repair as long as your alternator is working properly. My suggestion would be to have both the battery and charging system tested. The symptoms you described match exactly what I experienced, and it's better to address it soon before you end up stranded somewhere.

Thanks so much for sharing your experience, that's super helpful! I'm glad it turned out to be just the battery in your case. Would you mind sharing how much you ended up paying for the whole thing? Also curious if you've had any electrical gremlins pop up since getting it fixed? My mechanic quoted me quite a bit for diagnostics alone, so trying to get a sense if I'm being taken for a ride here.

Hey, good to hear back from you! Just wanted to follow up, after seeing the mechanic last week, they fixed my Z4's undervoltage issue completely. It cost me 290 € to replace the heavily discharged battery and register it to the system. Money well spent if you ask me! Since the repair, everything's working perfectly, no more flickering lights, no warning messages, and the car starts right up every time. Not a single electrical gremlin has shown up since. Based on what you're describing, sounds exactly like what I dealt with. I'd say get a second opinion if you're not comfortable with the quote, but from my experience, the diagnostic fee should be reasonable since it's a pretty common issue with these cars. Just make sure they're familiar with BMWs since the battery registration process is kind of specific to these models. Let me know how it goes! Always happy to help a fellow BMW owner.

I really appreciate all your help! Just got back from a different mechanic who was much more reasonable. Turns out you were spot on, it was definitely the battery causing all those crazy issues. Paid about 250 € for everything, including the diagnostic fee and registration. Way less than what the first place quoted me! The car's running like a dream now. No more heart-stopping moments wondering if it'll start, and all those warning lights have disappeared. Such a relief it wasn't something more serious. Looking back, I probably should've suspected the battery earlier given the car's age. The new mechanic was great too, really took the time to explain everything and didn't try to upsell me on unnecessary repairs. Goes to show how important it is to find a trustworthy specialist for these cars. Thanks again for steering me in the right direction. It's great to have knowledgeable folks to turn to when these issues pop up!