Sorry to revive old threads.. just wanna share 1 very unlikely experience..
My alfa is using the MY airbag system with 7 pieces that comes with facelift interior in many cases.
I noticed one reason the airbag passenger light was flashing, is when the red airbag light bulb is broken. In my experience, a previous owner had a curtain airbag issue (which I fixed) and his solution was to cut off the airbag light. Then, the passenger light flashes constantly, as a clever but annoying tactic to say something is wrong. He also removed that 2nd light as he noticed that, I assume!
Now that I fixed the airbags I learned how those lights work (by trial and error - mostly errors).
But yeah, using a OBD/ELM cable with temporary short from pin 7 to pin 3 and FiatECUScan you can quickly spot the error code(s).