Antitheft and Alarm Systems: Description and Operation

The Theft Deterrent System consists of the following components:

^ Anti-theft control unit
^ Left and right door switches
^ Left and right key detect and tamper switches
^ Rear hatch key switch
^ Engine hood switch
^ Automatic door lock motor
^ Automatic door lock switch
^ Left and right rear hatch switches
^ Lighting relay
^ Anti-theft relay
^ Headlights
^ Anti-theft indicator light
^ Anti-theft horn
^ Diode boxes

The arming sequence is started with the ignition switch in the LOOK position and all doors closed. This results in all theft related switches to be open to ground except the left and right key detect switches. The anti-theft indicator then flashes for about 30 seconds or until the arming sequence is completed. When the driver's door is locked using the door key, the automatic door lock switch and the automatic door lock motor internal switch will open, removing the ground signal from the anti-theft control unit input. Now all inputs to the anti-theft control unit are open to ground and the anti-theft indicator stays lit for about 8 seconds. The anti-theft system is now armed. If any of the theft related switches except the left or right key detect switches or the rear hatch key switch is grounded, the theft alarm is activated. The anti-theft unit does not allow the car to be started by not applying ground to the restart relay. The antitheft unit grounds and closes the lighting relay and the anti-theft relay contacts forcing the headlights to flash. At the same time the anti-theft control unit pulses a ground signal to the theft horn causing it to sound. The system alarm is cancelled when the antitheft control unit sees battery voltage at its ignition input or a ground signal at its key detect input.