Pontiac 2005 Montana Owner's Manual page 124

Content Theft-Deterrent
Your vehicle may have a theft-deterrent alarm system.
A light located on top of your instrument panel, near the
center of the vehicle next to the windshield, will flash
slowly to let you know that the system has been armed.
While armed, the doors will not unlock with the power
door lock switch.
2-26
Once armed, the alarm will go off if someone tries to
enter the vehicle without using the remote keyless entry
transmitter or a key, or turns the ignition to ON. The
horn will sound and the parking lamps will flash for up to
two minutes.
When the alarm is armed, the liftgate may be opened
with the remote keyless entry transmitter.
Arming with the Power Lock Switch
Your alarm system will arm when you use either power
door lock switch to lock the doors while any door or
the liftgate is open and the key is removed from
the ignition. If you would like to turn on power door lock
switch arming, see Vehicle Personalization on
page 2-57 .
When the security light flashes quickly the system is
ready to arm with the power door lock switches.
Then the security light will stop flashing and stay on
when you press the rear of the power door lock switch,
to let you know the system is arming. After all doors
and the liftgate are closed and locked, the security light
will begin flashing at a very slow rate to let you know
the system is armed.