OBD2 with airbag reader

[SideShow Bob]

ray 1970 is on the right track, that year series of GMC / Chevolets have have few glitches or problems that will cause the "Service Airbag" message to appear, or the airbag idiot light to come on.
One being the clock spring under the steering wheel, another is the connector behind the drivers side lower kick panel by the parking brake pedal and also the connector on the air bag CPU under the drivers seat beneath the carpet. And finally the inertia sensors (2) behind the front bumper, or their associated connectors.

Be sure to pull out the airbag fuse under the hood before diddling with any of these components.

And don't trust the code reader to be accurate. Mine originally started throwing the inertia sensor code, and would not reset after changing both, then later it started throwing another code, and now throws a code that I have had an airbag deployment.