Rolling Code
WARNING: This page is about a different car, the 2002 Pontiac Sunfire, 2002 Chevrolet Cavalier, 2001 Pontiac Sunfire, and 2001 Chevrolet Cavalier. However, it is still accessible from the selected car via links, so may be relevant.
The Remote Keyless Entry (RKE) system uses rolling code technology. Rolling code technology prevents anyone from recording message sent from RKE transmitter and using message in order to gain entry to vehicle. The term "rolling code" refers to the way RKE system sends and receives signals. RKE transmitter sends signal in a different order each time. RKE transmitter and Body Control Module (BCM) are synchronized to the appropriate order. If a programmed RKE transmitter sends a signal that is not in the order BCM expects, system will not function. This occurs after 256 presses of any button on RKE transmitter when it is out of range of vehicle.