2005 Toyota Prius Air Bag Diagnostic Code B1900?

We had body work done on the car and the drivers side seat was removed and then replaced, which seemed to trigger the code, but we don't know if somehow a sensor for the air bag was damaged or what this code means. When our mechanic scans the code for the airbag light, it comes up as B1900 but he can't seem to figure out what that means and the Toyota dealership has not been helpful. Can you please help? We can't get a safety inspection to pass with the airbag light illuminated, and that's our primary car. Does anyone know how to fix the problem?
Thank you.