GMC 2004 Sierra - Manual (Page 114)

If a door is opened without the key or the remote
keyless entry transmitter, the alarm will go off. Your
vehicle’s headlamps will flash and the horn will sound for
about two minutes, then will turn off to save the
battery power.
Remember, the theft-deterrent system won’t activate if
you lock the doors with a key or use the manual
door lock. It activates only if you use a power door lock
switch with the door open, or with the remote keyless
entry transmitter. You should also remember that
you can start your vehicle with the correct ignition key if
the alarm has been set off.
Here’s how to avoid setting off the alarm by accident:
• If you don’t want to activate the theft-deterrent
system, the vehicle should be locked with the door
key
after the doors are closed.
• Always unlock a door with a key, or use the remote
keyless entry transmitter. Unlocking a door any
other way will set off the alarm if the system
has been armed.
If you set off the alarm by accident, unlock any door with
the key. You can also turn off the alarm by pressing
UNLOCK on the remote keyless entry transmitter or by
placing the key in the ignition and turning it to START.
Testing the Alarm
The alarm can be tested by following these steps:
1. From inside the vehicle, lower the driver’s window
and open the driver’s door.
2. Activate the system by locking the doors with the
power door lock switch while the door is open, or
with the remote keyless entry transmitter.
3. Get out of the vehicle, close the door and wait for
the security light to go out.
4. Then reach in through the window, unlock the door
with the manual door lock and open the door. This
should set off the alarm.
If the alarm does not sound when it should but the
vehicle’s headlamps flash, check to see if the horn works.
The horn fuse may be blown. To replace the fuse, see
Fuses and Circuit Breakers on page 5-126.
If the alarm does not sound or the vehicle’s headlamps do
not flash, the vehicle should be serviced by an authorized
service center.
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