....after I installed a dual lighter socket receptacle inside (behind the radio) so I can plug in both my Garmin GPS and my XM radio. I don't like wires running everywhere in sight and have done this on many other vehicles. I didn't get near anything air bag related, but now the Air Bag light is flashing.
my guess is you unplugged the passenger airbag indicator and then turned on the the key..(open circuit throws a code) the little yellow light on the right side of the heater controls
if you don't want it to happen again next time take the whole light assembly out of the plastic surround to avoid disconnecting it.