GMC 2009 Sierra - Manual (Page 174)

Passenger Airbag Status Indicator
Your vehicle has the passenger sensing system.
Your overhead console has a passenger airbag status
indicator.
When you start the vehicle, the passenger airbag status
indicator will light ON and OFF, or the symbol for on
and off, for several seconds as a system check. Then,
after several more seconds, the status indicator will
light either ON or OFF, or either the on or off symbol to
let you know the status of the right front passenger’s
frontal airbag.
If the word ON or the on symbol is lit on the passenger
airbag status indicator, it means that the right front
passenger’s frontal airbag is enabled (may inflate).
{ CAUTION:
If the on indicator comes on when you have a
rear-facing child restraint installed in the right
front passenger’s seat, it means that the
passenger sensing system has not turned off
the passenger’s frontal airbag. A child in a
rear-facing child restraint can be seriously
injured or killed if the right front passenger’s
airbag inflates. This is because the back of the
rear-facing child restraint would be very close
to the inflating airbag. Do not use a rear-facing
child restraint in the right front passenger’s
seat if the airbag is turned on.
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