That's strange, if the light is on then there should be a fault code. Have you tried clearing it? (using the diagnostic machine) Does it come straight back?
The airbag sensors are under the driver and passenger seats, 90% of airbag faults seem to be related to them. It's usually triggered if you have water in the footwells, (which from your previous posts i know to be the case) so i would sort that out first.