2004 GMC Sierra 1500 Pickup Owner's Manual - Page 204

Passenger Air Bag Status Indicator If your vehicle has the passenger sensing system your rearview mirror will have a passenger air bag status indicator. 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 air bag. If the word ON or the on symbol is lit on the passenger air bag status indicator, it means that the right front passenger's frontal air bag is enabled (may inflate). {CAUTION: Passenger Air Bag Status Indicator - United States 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 air bag. A child in a rear-facing child restraint can be seriously injured or killed if the right front passenger's air bag inflates. This is because the back of the rear-facing child restraint would be very close to the inflating air bag. Don't use a rear-facing child restraint in the right front passenger's seat unless the air bag has been turned off. Passenger Air Bag Status Indicator - Canada When the ignition key is turned to RUN or START, the passenger air bag 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, 3-40