Normal Operation
WARNING: This page is about a different car, the 2004 Mercury Mountaineer and 2004 Ford Explorer. However, it is still accessible from the selected car via links, so may be relevant.
The remote transmitter and the vehicle security module use a rolling code to prevent the codes from being "captured" by a code grabber. The system advances the counter in the remote transmitter and in the vehicle security module every time a remote transmitter button is pressed.
All remote transmitters must be present to begin diagnosis of the remote keyless entry (RKE) system.