Just bought a 2001 bugeye wrx wagon, the one key I have
for it has lock and unlock buttons but I assume the battery
is dead as it doesn't lock/unlock the doors.

Can I just change the battery for it to work or does
it need to be recoded at all?

 

Should be just a case of change the battery, you may have to operate it a couple of times to get it in sync.

 

cr1620 battery, 3v

 

Excellent, cheers guys.

 

Also don't forget that if you have the Sigma Alarm (Normally a single button remote fob) then there will not be a battery in the actual key as it interferes with the Cat1 alarm.

 

Oh, we'll I put a battery in the key today but it doesn't
lock/unlock the doors.

I have a sigma fob which is working fine.

Should I remove the battery from the key then even though it
doesn't work?

 

Yes buddy, I have the same, never had a battery on the key part. There's a transponder in the key but it doesn't need batteries. Subaru I believe removed them when the sigma alarms are fitted. You can leave the battery on if you want.