Antitheft and Alarm Systems: Description and Operation
CIRCUIT OPERATIONWhen the Theft Deterrent System has been turned on, or armed, it will automatically operate the alarms. It sounds the vehicle horns and flashes the Exterior Lights. This happens when any of the doors are opened, or if the forced entry switches on either door or trunk locks are closed.
Alarms - The light and horn alarms are controlled by the Theft Deterrent Module. The Theft Deterrent Module will ground pin F whenever a tamper input is detected. When this happens the Theft Deterrent Relay closes and energizes the Twilight Relays. The Horn Relay is energized by the Theft Deterrent Module and current flows through the Theft Deterrent Diode to complete the circuit. The Theft Deterrent Diode prevents the Theft Deterrent Relay from energizing when the horn is operated. The Module then opens the BLK/WHT (624) circuit to turn off the alarms. The alarms will pulse on and off every second for 2 to 4 minutes after the system has been triggered by a tampering or forced entry input.
Arming - The arming sequence begins with the Ignition Switch turned off. This removes battery voltage at terminal K, the Ignition Input. As a door is opened ground is applied to terminal J, the Tamper Input. The system is not armed yet so grounding the Tamper Input does not set off the alarms. With a Power Door Lock Switch momentarily moved to LOCK, battery voltage is momentarily applied to terminal G, the System Arm Input. Lastly, closing all open doors will remove ground from terminal J and complete the arming sequence. The system is now armed.
Cancellation - The arming sequence can be cancelled. This is done by moving a Power Door Lock Switch to the UNLOCK position before the door is closed to complete the arming of the system. Battery voltage is applied momentarily to terminal M with the Door switch in UNLOCK. This cancels the arming.
Disarming - When one of the doors is unlocked with a key, a grounding switch in the Front Door Lock Cylinder closes. This grounds terminal H of the Module, the Disarm Input. The system is disarmed and no alarms will operate when a door is opened. Turning the Ignition Switch to RUN will also disarm the system by applying battery voltage to terminal K. However, the only way to deactivate the alarms when they are sounding is to unlock one of the doors with the key.
Tampering - The alarms are set off when terminal J, the Tamper Input, is grounded. The door Jamb switches close to ground with the door open. In addition, the Forced Entry switches and Trunk Lid Tamper Switch close when there is motion between a door or the trunk and its switch. This happens when a lock is forced or removed. The Forced Entry switches then ground the Tamper Input and set off the alarms.
Keyless Entry Module - The Keyless Entry Module will simulate the action of the Door Jamb Switches (terminal C9) and Power Door Lock Switches (terminal C3) when locking the doors with the portable transmitter so that the Theft Deterrent System can be armed. The Keyless Entry Module will also disarm the Theft Deterrent System (terminal C8) when unlocking the doors with the portable transmitter by grounding terminal H the System Disarm Input momentarily. The Keyless Entry Module can also cancel arming (terminal C2).