GMC Sierra 2010 Owner's Manual page 132

Additional Factors Affecting System
Operation
Safety belts help keep the passenger in position on the
seat during vehicle maneuvers and braking, which helps
the passenger sensing system maintain the passenger
airbag status. See Safety Belts and Child Restraints
in the Index for additional information about the
importance of proper restraint use.
If the shoulder portion of the belt is pulled out all the
way, the child restraint locking feature will be engaged.
This may unintentionally cause the passenger sensing
system to turn the airbag off for some adult size
occupants. If this happens, let the belt go back all the
way and start again.
A thick layer of additional material, such as a blanket
or cushion, or aftermarket equipment such as seat
covers, seat heaters, and seat massagers can affect
how well the passenger sensing system operates.
2-90
We recommend that you not use seat covers or other
aftermarket equipment except when approved by GM
for your specific vehicle. See Adding Equipment to Your
Airbag-Equipped Vehicle on page 2 91 for more
information about modifications that can affect how the
system operates.
The on indicator may be lit if an object, such as a
briefcase, handbag, grocery bag, laptop or other
electronic device, is put on an unoccupied seat.
If this is not desired, remove the object from the seat.
WARNING:
Stowing of articles under the passenger seat or
between the passenger seat cushion and
seatback may interfere with the proper operation
of the passenger sensing system.