what I'm about to say is very very ropey but if I do remember correctly; the wire underneath the seat is the 'Seat belt pretension-er' (basically a little gizmo that tightens your seat belt when you crash) if that has a fault/unplugged it will flash four times indeed, one flash means drivers airbag two flashes means passenger airbag fault and three flashes means passenger pretension-er fault it may be worth taking the air bag out (as in the whole component) and checking the wiring connections behind that before investigating, I had an issue where i cut my old one because I had some pimping aftermarket steering wheel yo!! was so pimping that the horn connections were faulty to say the least, when ever I wanted to turn right the horn would sound, mildly embarrassing