The system will not arm if the doors are locked using the manual lock control (by hand) or if the locks are actuated by an inside occupant after the door is closed.
There are three switches used to ARM and DISARM the system. They are located in the left front and right front doors, and in the liftgate. These switches use resistors internal to the switch to send a signal to the Body Control Module (BCM).
Otherwise, if you want to DisArm :
Find the WHITE / Dark GREEN (-) wire in the Driver Kick Panel / Door Boot.Connect one end of a 665 Ohm Resistor to the WHITE / Dark GREEN (-) wire.Connect the other end of the 665 Ohm Resistor to Chassis Ground.This will DisArm the Alarm until the Resistor is removed