GMC 2005 Sierra 1500 Pickup Owner's Manual page 76

The airbag system is designed to work properly under a
wide range of conditions, including off-road usage.
Observe safe driving speeds, especially on rough
terrain. As always, wear your safety belt. See Off-Road
Driving with Your Four-Wheel-Drive Vehicle on
page 4-20 for more tips on off-road driving.
Single Stage vs. Dual Stage Airbags
Depending on the weight of your vehicle you will have
either "Single Stage Airbags" or "Dual Stage Airbags".
Vehicles that have a passenger sensing system
also have dual stage airbags. If the rearview mirror in
your vehicle has a passenger airbag status indicator
printed on it, your vehicle has the passenger sensing
system and therefore, it has dual stage airbags. If
the rearview mirror in your vehicle does not have a
passenger airbag status indicator printed on it, then your
vehicle does not have the passenger sensing system
and it has single stage airbags. See Passenger
Airbag Status Indicator on page 3-36 or Passenger
Sensing System on page 1-76.
1-70
Dual Stage Airbags
If your vehicle has frontal airbags with dual stage
deployment, the amount of restraint will adjust according
to crash severity. Your vehicle is equipped with electronic
frontal sensors which help the sensing system distinguish
between a moderate and a more severe frontal impact.
For moderate frontal impacts, these airbags inflate at a
level less than full deployment. For more severe frontal
impacts, full deployment occurs. If the front of your
vehicle goes straight into a wall that does not move or
deform, the threshold level for the reduced deployment is
about 10 to 16 mph (16 to 25 km/h), and the threshold
level for a full deployment is about 20 to 25 mph
(32 to 40 km/h). (The threshold level can vary, however,
with specific vehicle design, so that it can be somewhat
above or below this range.)
Vehicle's with dual stage airbags are also equipped with
special sensors which enable the sensing system to
monitor the position of both the driver and passenger
front seats. The seat position sensor provides
information which is used to determine if the airbags
should deploy at a reduced level or at full deployment.