I did a bit of work on a sedan tonight regarding this. for a 2001 v35 I saw (and checked) pass airbag,drv airbag, pretensioners - all checked ok.
if there is ANY fault with the system them the light will flash until the fault is cleared. the system checks itself everytime the ign is turned on and started. if there is a serious fault then doing a diagnostic scan on it is the only way to sort it.I had one came back with a short on the drivers air bag. that was due to the thing not being properly plugged in and the contacts on the bag were closed ( they do this as a safety precaution.) temporarily and the system logged a fault.