C8 Key Battery Warning

Sounds like a flat key fob battery. Have you tried replacing it? It's usually a CR2032. Does the spare key work?

Thanks! I haven't replaced it yet, but will try. Where do I find a CR2032, and do I need special tools to open the key?

You can get a CR2032 at most supermarkets or electronics stores. Usually, a small flat-head screwdriver or even a knife will pry it open. If you're not comfortable, a locksmith or workshop can do it. But based on the symptoms, I'd bet on the battery. They should check for error codes anyway.

Thanks! It was the key fob battery. Replaced it today, and everything's working. The error is gone, and keyless entry works. New battery plus labor cost me 37€.