Antitheft and Alarm Systems: Description and Operation

The Content Theft Deterrent System is designed to sound the horns and flash the exterior lamps when the system is armed and when the Body Control Module (BCM) detects an unauthorized entry. An unauthorized entry can be any of the following conditions:
^ Disconnection/reconnect of the battery for more than 1 second.
^ Door opened.
^ Forced entry into the trunk.
^ The ignition switch transitions from the LOCK position.

Alarms
Operation of the horns and exterior lamps when activated, is controlled by the BCM. When the alarm is active, the BCM cycles the Horn, Low Beam, and Park Lamp Relays on and off once per second. During this cycle ground is applied the respective relay's coil and then removed. This causes the relay to energize and de-energize.

The BCM will remain in the "Alarm" state for three minutes or until a valid input to disarm it is received.

Arming
The arming sequence begins when the ignition is turned to the LOCK position and a door is opened. The next step occurs when the doors are locked either by the electronic door lock switches or by the RKE Transmitter (Key FOB). When the last door is closed, the BCM enters a "Delayed" state for 30 seconds and then proceeds to the "armed" state unless it receives a valid input to disarm. The Security Indicator lamp remains on until it enters into the "Armed" state, see Security Indicator.

The arming sequence can be canceled by unlocking the doors electronically prior to closing the door. When the doors are unlocked, the BCM will arm and disregards the door being closed.

Disarming
When the left front door is unlocked with a key, the Door Lock Switch closes. This grounds the door's input to the BCM. The system is then disarmed and the alarm state will not become active when the door is opened.

Turning the ignition switch to any position out of LOCK will not disarm the system when the alarm is active. Remote Keyless Entry (RKE)

The keyless entry receiver is an internal part of the BCM. When the receiver receives a transmission from a Key FOB, it sends a message to the BCM to unlock the doors. This message will only be sent to the BCM if the receiver recognizes the transmission as a valid Key FOB.

Security Indicator
The BCM grounds circuit XP840 to illuminate the Security Indicator Lamp. The Security Indicator Lamp reminds the operator to arm the system by flashing the lamp. It indicates the system is arming when it stays On steady. The system is armed when the lamp is Off.