In the trunk, pull the driver's side lining and you'll find a 2-pin male connector sitting there open. Turn the ignition to 'on', then short those two pins. The doors will cycle locked/unlocked. Hold the 'lock' button on the remote until the doors cycle locked/unlocked again. Turn the ignition to off, the doors will cycle one last time. Finally, test the remote.
A handy video, not the best quality, but gives the key points:
[video=youtube;BAeowsKYydM]http://www.youtube.com/watch?v=BAeowsKYydM[/video]