Door Ajar Switches
WARNING: This page is about a different car, the 2002 Pontiac Grand Prix. However, it is still accessible from the selected car via links, so may be relevant.
The CTD system uses the door ajar switches in the door latch assemblies as one method to activate the alarm. The body control module (BCM) monitors all door ajar switches via a discrete input from each door ajar switch. If the BCM receives a ground signal from a door ajar switch when the CTD system is armed, the BCM activates the alarm.