Supras of this year did not have OBD 2. They are OBD 1.
Anyways, you can do a code check from the diagnostic connector to see what is wrong.
90 percent fo the time when the Airbag light is on, it is time for its service. The Supras this old requires a service check at the first 10 years and then every two years there after ( im not sure) . You can take it to a shop with diagnostic tools and turn that light off if nothing is wrong . My friends 91 Supra had this problem andits good now after resetting the light.
Another thing that can trigger the Airbag light is if the Airbag computer was unplugged for too long causing a loss of power. This happened to me and I had it reset.
Hope this helps.