Ford Mustang (1999-2004) Service Manual: Principles of Operation

NOTE: Battery power and ground must be remove before disconnecting the GEM connectors to avoid setting false codes.

Power Locks Operation

The power locks feature allows the customer to lock and unlock the doors via momentary switches located on the driver and passenger door. When the GEM detects a momentary press of the driver or passenger lock button, the GEM will supply power to the driver or passenger lock actuators for approximately 250 ms from relays internal to the GEM. When the GEM detects a momentary press of the driver or passenger unlock button, the GEM will supply power to the driver or passenger unlock actuators for approximately 250 ms from relays internal to the GEM.

Remote Keyless Entry Door Locks Operation

The remote entry feature allows the customer to unlock the driver door, unlock all doors, and lock all doors using a valid remote transmitter as long as the ignition switch is not in RUN or START. The driver door is unlocked whenever the GEM detects a valid remote transmitter unlock transmission. All the doors are unlocked when the GEM detects a second valid remote transmitter unlock transmission within three seconds of the first transmission. All the doors are locked when the GEM detects a valid remote transmitter lock transmission. If the GEM detects a second valid remote transmitter lock transmission within three seconds of the first transmission, the doors will lock again, the horn will sound for 20 ms and the parking lamps will flash for 200 ms to indicate the doors are locked. If the GEM detects the driver or passenger door is ajar during the second lock transmission, the doors are locked again and the horn is sounded twice. If the GEM detects a valid remote transmitter lock transmission within three seconds of detecting a valid remote transmitter unlock transmission, the GEM will lock all the doors.

Remote Keyless Entry Luggage Compartment Operation

The luggage compartment lid is released whenever the GEM detects a valid remote transmitter luggage compartment release transmission.

Panic Alarm Operation

The panic alarm feature allows the vehicle to initiate an alarm for 2.75 minutes to identify itself using a valid remote transmitter. The panic alarm is activated whenever the GEM detects the ignition switch is in the OFF position or if the key is removed from the ignition, and the GEM detects a valid PANIC response from the remote transmitter. When the panic alarm is activated, the GEM:

• illuminates the courtesy lamps.
• flashes the parking lamps.
• toggles the horn on and off.

The panic alarm is deactivated whenever GEM detects:

• if the key causes a transition of the ignition switch circuits to

• ACC.
• RUN.
• START.

• the remote transmitter

• panic button.
• unlock button.

The panic alarm is also deactivated after 2.75 minutes have gone by.

Remote Transmitter Programming Operation

This feature allows the customer to program up to four different transmitter identification codes (TIC) for four remote transmitters to the vehicle at any time. For additional information, refer to Programming-Keyless Entry Remote Transmitter .