GM Service Manual Online
For 1990-2009 cars only

The remote keyless entry system uses rolling code technology. Rolling code technology prevents anyone from recording the message sent from the transmitter and using the message in order to gain entry to the vehicle. The term "rolling code" refers to the way that the keyless entry system sends and receives the signals. The transmitter sends the signal in a different order each time. The transmitter and the remote control door lock receiver (RCDLR) are synchronized to the appropriate order. If a transmitter sends a signal that is not in the order that the RCDLR expects, the keyless entry system will not function. Loss of synchronization will occur if the programmed transmitter is activated more than 16 times while out of range of the vehicle.

The keyless entry transmitters do not require a manual synchronization procedure. If needed, the transmitters automatically resynchronize when any button on the transmitter is pressed within range of the vehicle. The transmitter will operate normally after the automatic synchronization.