Normal Operation
WARNING: This page is about a different car, the 2005 Mercury Mountaineer and 2005 Ford Explorer. However, it is still accessible from the selected car via links, so may be relevant.
The remote keyless entry (RKE) 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 RKE transmitter and in the vehicle security module every time a RKE transmitter button is pressed.
All RKE transmitters must be present to begin diagnosis of the RKE system.