My normal key fob does not work but the spare key works.

It does not open or close the doors but can start the car and drive. My spare key is perfect.

I think it's the battery, what are your views?

Yes the battery would be my first thing to check (it's a CR2032)

The battery is only used to open and lock the car, the transponder is the bit that enables the car to start

Yes the battery would be my first thing to check (it's a CR2032)

The battery is only used to open and lock the car, the transponder is the bit that enables the car to start

Thanks, I will get a set of batteries over the weekend