Look under the passenger seat at the rear and you will see a connector.  
Unplug it while the engine is off, then plug it back in.  Start the
engine and see if the air bag light goes out.  This works on mine, and
it will work normally until someone sits in the rear seat on the
passenger side and bumps the connector with their foot. I son't know if
the connector is loose or it resets the alarm.