Operation CHARM: Car repair manuals for everyone.
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Principles of Operation

PRINCIPLES OF OPERATION

The generic electronic module (GEM) monitors the door ajar switches, the hood ajar switch and the luggage compartment lid/liftgate disarm switch. When the GEM receives a signal from one or more of the monitored switch(es) indicating unauthorized entry into the vehicle, the GEM intermittently grounds the horn relay and also intermittently sends voltage to the turn signal lamps. The horn relay closes, supplying voltage to the horn. The GEM cycles the ground to the horn relay and voltage to the turn signal lamps, on and off, while the system is activated. An activated alarm can either be deactivated or disarmed. Pressing the PANIC button on the RKE transmitter will deactivate the perimeter alarm, but will not disarm the alarm. The perimeter anti-theft feature (or an activated alarm) can be disarmed when either an unlock request is made through the remote keyless entry (RKE) transmitter or if the driver door is unlocked with a key, or the ignition switch is turned to the ON position using a valid programmed key. The perimeter anti-theft feature can be armed by either pressing the LOCK button on the RKE transmitter or pressing the door lock control switch to the LOCK position with the accompanying door open, then close the door. The GEM monitors the key-in-ignition switch and does not allow the perimeter anti-theft feature to arm until after the key is removed from the ignition switch, all doors/hood/luggage compartment lid/liftgate are closed and 20 seconds have elapsed after locking the vehicle. Each input has its own 20 second pre-arm phase, depending on when they were closed after the arm command was given. After all of these criteria have been met, the anti-theft feature will arm.