BMW Key Fob Dead? Warning Lights May Signal Battery Issue

I had the same issue with my 2003 BMW 5 Series diesel. The symptoms were identical, key fob stopped working and dashboard warnings popped up. Got it checked at the garage last month. Turned out it wasn't just the key battery. The key's internal circuit board had corroded slightly, affecting the transponder signal. The mechanic cleaned the contacts and replaced both the key battery and a small internal component. The repair wasn't particularly serious, but it needed proper diagnostic equipment to verify the transponder was working correctly after the fix. My car had about 95,000 km at the time. The warning messages cleared up right after the repair, and the keyless entry has been working perfectly since then. My suggestion would be to have a certified BMW specialist look at it rather than attempting a DIY battery replacement, since there could be more to it than just a dead battery.

Thanks for sharing your experience. That's really helpful info about the corroded circuit board, definitely seems similar to what I'm experiencing. Would you mind letting me know roughly how much the repair ended up costing you? Also, just curious if you've had any other issues pop up with the key fob since getting it fixed?

Hey there! Following up on your questions, yes, the key fob has been working flawlessly since I got it fixed. The annoying "Battery in key empty" warning completely disappeared right after the repair, which was a huge relief. The total bill came to 37 € for the whole job, that covered the new battery, cleaning the circuit board, and reprogramming everything to work with the car's system. Honestly, it was money well spent considering how smoothly everything's working now. Haven't had a single problem with the key fob in the months since. No more dashboard warnings, the remote locking works every time, and the transponder communicates perfectly with the car. It's actually kind of nice not having to worry about whether the key will work each time I approach the car! If you're experiencing similar symptoms, I'd definitely recommend getting it checked out by a specialist. The repair was pretty straightforward and quick, I was in and out of the shop in no time.

Thanks again for all the detailed info! I actually took your advice and went to get it checked out yesterday. You were spot on, it was more than just a dead battery. The mechanic found similar issues with corrosion on the circuit board, plus a loose connection that was causing the warning messages. The repair cost me 45 € in total, a bit more than yours but still reasonable. They replaced the battery, cleaned everything up, and made sure all the connections were solid. They even tested the transponder signal strength before and after to confirm everything was fixed properly. Got to say, it's such a relief having it all sorted. The key works perfectly now, no more standing in the rain hitting the unlock button multiple times! Really glad I didn't try to fix it myself. Sometimes it's worth paying a professional to do things right the first time. Thanks for helping me avoid another frustrating mechanic experience. The BMW specialist you suggested was definitely the way to go!