I have a 97 Rodeo with the OEM Fujitsu Ten Keyless Security System.
Here's the procedure I used to reprogram my remotes:
Remove the key from one remote so I could have both remotes in the back seat with me.
Turn the key ON
Push the green button on the back of the security system unit with a pen. The unit is under the driver's seat. Hold the button for a few seconds until the security light ( Left of the instrument cluster on the dash ) lights steady. It takes a few seconds to turn on, and then it will be steady for a few seconds.
While the light is STEADY, press the DOOR/LOCK button ( top button ) on the remote. The interior lights flash and the security light goes out.
Push the green button again until the security light goes on, remains steady for a few seconds, and then starts blinking. It will blink for a few seconds.
While the light is BLINKING, press the TAILGATE/HATCH button ( bottom button ) on the remote. The interior lights flash and the security light goes out.
Repeat procedure for the other remote.
That's all there was to it. Good luck!