Actually it's a Maintenance item-
Resetting the ECU does nothing for an airbag light/code. Airbag codes are set and stored in the airbag control module and you can't clear them by disconnecting the battery.
It is possible to read the code by using the diagnostic procedure in the service manual, whereby you plug the diagnostic connectors together and count the flashes of the airbag light. Alternately the code can be read by the dealer using their scanner. Once the code is known, the source of the problem can be identified.
Anyway if you're already done what Unabomber suggested and it worked, just file this info away for another time if it happens again.