GMC 2009 Sierra - Manual (Page 30)

Shoulder Belt Height Adjuster
Your vehicle has a shoulder belt height adjuster for the
driver and right front passenger.
Adjust the height so that the shoulder portion of the belt
is centered on your shoulder. The belt should be
away from your face and neck, but not falling off your
shoulder. Improper shoulder belt height adjustment
could reduce the effectiveness of the safety belt
in a crash.
To move it down, squeeze
the buttons (A) on the
sides of the height adjuster
and move the height
adjuster to the desired
position.
You can move the adjuster up just by pushing up on the
shoulder belt guide.
After you move the adjuster to where you want it, try to
move it down without squeezing the buttons to make
sure it has locked into position.
Safety Belt Pretensioners
Your vehicle has safety belt pretensioners for front
outboard occupants. Although you cannot see them,
they are part of the safety belt assembly. They can help
tighten the safety belts during the early stages of a
moderate to severe frontal, near frontal, or rear crash if
the threshold conditions for pretensioner activation
are met. And, if your vehicle has side impact airbags,
safety belt pretensioners can help tighten the safety
belts in a side crash or a rollover event.
Pretensioners work only once. If they activate in a
crash, you will need to get new ones, and probably other
new parts for your safety belt system. See Replacing
Restraint System Parts After a Crash on page 1-71.
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