Keyless Entry: Description and Operation

The keyless entry remote transmitter operates the following functions:
^ Unlocking the driver door.
^ Unlocking all doors.
^ Unlocking the liftgate.
^ Locking all doors.
^ Activates and deactivates the panic security feature which sounds the horn and flashes the turn signal indicator lamps.

Inputs and Outputs
The keyless entry/computer operated lock system receives inputs from the following:
^ Ignition switch.
^ Door lock switches.
^ Keyless entry remote transmitter.

The keyless entry/computer operated lock system distributes outputs to the following:
^ Central timer module (interior lighting).
^ Door lock actuators.
^ Liftgate release actuator.
^ Horn relay.
^ Exterior lighting control

Locking/unlocking
To unlock the driver door, press the UNLOCK button on the keyless entry remote transmitter once. This action will also disarm the anti-theft alarm system (if equipped).

To unlock all doors, press the UNLOCK button on the remote transmitter a second time within three seconds of unlocking the driver door.

To unlock the liftgate press the blue TRUNK button twice within three seconds on the remote transmitter. Two presses are required to prevent inadvertent liftgate opening.

To turn on the interior lamps, press the UNLOCK button on the remote transmitter.

To lock all doors and arm the anti-theft alarm (if equipped) press the LOCK button on the keyless entry remote transmitter once.

To confirm that both doors have locked, the turn signal lamps will flash once.

Central Security Module
The central security module contains a radio receiver that receives a signal from the keyless entry remote transmitter through the central security module antenna. Once a signal is received, the central security module sends the appropriate command to the door lock actuators, the horn relay, the liftgate release actuator, central timer module, and the exterior lights.

The central security module is equipped with battery back-up which holds the programmed transmitter(s) memory in the event of vehicle battery disconnection.

Security Mode Operation
The central security module also controls the panic mode function.

Upon activation of the panic mode by pressing the keyless entry remote transmitter PANIC button, the central security module sends a signal to activate the horn and flash the turn signal indicators for a duration of 120 seconds.

The central security module cancels the panic alarm if the same PANIC button is pressed again or the ignition switch is turned to the RUN position.

PRINCIPLES OF OPERATION
When a remote transmitter button is depressed, it transmits the appropriate command to the Central Security Module (CSM) as a radio frequency. The CSM receives the command from the remote transmitter through an antenna, that is incorporated into the harness connected to the CSM through CSM C451a.

When the CSM receives a command from a remote transmitter, it then sends the appropriate output to control the desired devices. These output devices include:
^ The driver and passenger door lock units.
^ The Central Timer Module (CTM).
^ The right and left flasher relays.
^ The liftgate release motor.

The CSM sends a signal to the CTM when courtesy lamp illumination is required.

The CSM is equipped with an Erasable Programmable Read-only Memory (EPROM) chip. This EPROM stores the Transmitter Identification Codes (TICs) for any transmitters that have been programmed to that vehicle. The codes are stored in a non-volatile memory, protecting them from power loss. Such a power loss could occur if the vehicle battery has to be disconnected for vehicle repair, or if the battery were allowed to discharge.