Driver Door Key Cylinder Switch
WARNING: This page is about a different car, the 2008 Cadillac CTS. However, it is still accessible from the selected car via links, so may be relevant.
The CTD system uses the driver door cylinder switch as a means to disarm the CTD system. The BCM receives the status of the driver door cylinder switch based on a discrete input from the switch. When the driver door key cylinder is rotated the CTD system will immediately disarm.