As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
BIL - ON TAXI OUT, FLIGHT CREW NOTED NR 1 ENGINE FIRE WARNING. BOTH ENGINES SECURED WITHOUT INCIDENT AND AIRCRAFT WAS TOWED BACK TO HANGAR. FALSE FIRE WARNING DUE TO MOISTURE ON SENSOR. CLEANED SENSOR AND ELECTRICAL CONNECTION, SYSTEM CHECKS GOOD.