I've got an '04 Discovery SE and the door locks don't work anymore. I use to be able to lock and unlock the doors by pressing the key.

I just replaced the car battery with one with higher cranking amps. So its not that.

Could this be a fuse, or is there a little battery in the key itself?

 

There is a battery in the key, does the little light on the key operate when you press either button? If not then I would suspect the key, if it does I'd still replace the key battery because I've seen weak batteries operate the light but not the alarm/door locks.

 

Key is working now, 3 doors are fine. But front passenger lock does not work by remote.

All the fuses are good, so not sure why it won't work