hi we had this problem on my wifes punto a few months ago. tried reading the diagnostic codes but there was no codes stored. a web search brought up known problems with the wiring to the passenger airbag. this wiring runs above the glovebox with i think a connector somewhere near that glovebox. fiat said sometimes shutting the glovebox hard can cause the light to come on. it could be as simple as the connector has worked loose. but i was told that only fiat could turn off the airbag light.

so rang the local fiat garage up, knew straight away what i was talking about and would cost, if i remember rightly about £80.00. car booked in job done £80.00 lighter but at least the light is now off and hopefully the airbag is ok if ever it is needed.