As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING CLIMB OUT OF ANC THE CHECK FIRE DTC LIGHT ON THE MASTER WARNING PANEL BECAME INOPERATIVE. THE CREW ATTEMPTED TO FIX THE PROBLEM WITH PROCEDURES ADVISED DURING A DISCUSSION WITH MAINTENANCE. THE PROBLEM PERSISTED AND THE ITEM MAY NOT BE DEFERRED SO THE FLIGHT IS RETURNING TO ANC.