Liftgate Ajar Switch
WARNING: This page is about a different car, the 2009 Saturn Vue. However, it is still accessible from the selected car via links, so may be relevant.
The CTD system uses the liftgate ajar switch as a status indicator to activate the alarm. The liftgate ajar switch is monitored by the BCM a discrete input from the switch. If the BCM receives a status signal from the liftgate ajar switch indicating it was opened without the keyless entry transmitter, the BCM activates the alarm.