it isnt disarming the factory alarm.More then likely who ever installed it used ttaps. If they did do it wire to wire like it was intended and it will work better.

FACTORY ALARM DISARM PURPLE (-) @ BCM, Connector C2, Pin 24, See NOTE *2

NOTE *2 the BCM (Body Control Module) is located just below the DRIVERS SIDE of DASH and to the LEFT of the STEERING COLUMN.