If you have had an airbag disconnected for service (as an example, when replacing a window motor, often an aftermarket shop will disconnect the airbag then turn on the ignition to test the window motor) the only way to reset the light is to take it to your dealer. If disconnection is required on future work, only disconnect the airbag with the ignition off. You must have the airbag connected when the ignition is on (like when testing the new window motor) to avoid the problem.
gmills, February 2008