Liftgate Ajar Switch
WARNING: This page is about a different car, the 2009 Pontiac Torrent and 2009 Chevrolet Equinox. 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 via a discrete input. If the BCM receives a signal indicating a liftgate is opened when the CTD system is armed, the BCM activates the alarm.