I have this from an earlier post:

this one was for a '94 Pathfinder)

- Turn off the alarm.

- Take the key out of the ignition.

- The alarm control box is under the driver's seat.  There
 is a hole in the top of it (it may have a piece of clear tape over
 it).  Push down through the hole until the alarm beep stops
 and a rythmic beep starts.

(If I remember correctly, you have to do the next step before the
beeping in the above step stops or you have to start over)

- Press the lock button on each new remote once.

- Put the key in the ignition. Turn the ignition on and
 back off.

- The remote should now work.