i have a 94 ford probe gt the air bag light flashes 51 can some one tell me what this is please

 

My airbag light flashes 8 then 1. I cannot find a code for that sequence. When I start the car, all the lights are on, then turn off. The airbag light then blinks 8 times, pauses 2 sec then blinks once. There is then a 5 sec pause and the 8-1 sequence starts again