2003 GMC Yukon Owner's Manual - Page 90

If a person of adult-size is sitting in the right front passenger's seat, but the off indicator is lit, it could be because that person isn't sitting properly in the seat. If this happens, turn the vehicle off and ask the person to place the seatback in the full upright position, then sit upright in the seat, centered on the seat cushion, with the person's legs comfortably extended. Restart the vehicle and have the person remain in this position for about two minutes. This will allow the system to detect that person and then enable the passenger's air bag. {CAUTION: If the air bag readiness light in the instrument panel cluster ever comes on and stays on, it means that something may be wrong with the air bag system. If this ever happens, have the vehicle serviced promptly, because an adult-size person sitting in the right front passenger's seat may not have the protection of the frontal air bag. See "Air Bag Readiness Light" in the Index for more on this, including important safety information. Aftermarket equipment, such as seat covers, can affect how well the passenger sensing system operates. You may want to consider not using seat covers or other aftermarket equipment if your vehicle has the passenger sensing system. 1-84