what does the airbag light on indicate?

There is a failure somewhere in the ABS system. typical failures are in the various sensors located throughout the car body [bumpers, etc.] or, a common failure is in the 'clockspring' in the steering wheel itself. there was also a recall [I believe] around that time about a bad connector for the passenger seat. but the only way to know is with Tech II. when the SRS system faults, it disables itself. So, at this point, you have no functional airbags.

Sorry, first line should read "SRS system" not "ABS system".

Based on my experience with the NG900/OG 9-3 the air bag light usually comes on because like Tom said the wiring connection comes loose. However you would need a code reader to tell for sure. Otherwise you could make sure the harnesses under the front seats are tight, and then unplug the battery for about 15 min to reset the code, and if the issue persists then you should go to a garage.