My 2000 doesn't lock or unlock any of the doors. Lol. I've been wondering about this.
Either you don't have the RS3k, or it's been disabled.?? Mine ('97) has no such unlock/lock behavior.
Either you don't have the RS3k, or it's been disabled.
Do you have the "Security" light on your center console or dash? Do you have a module under your driver seat?
If yes, you should be able to follow the instructions posted above to enable the lock/unlock feature.
If no, your rig is not equipped with the RS3k that enables this function.