As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
LEFT ENGINE FIRE WARNING ILLUMINATED DURING FLIGHT FOR APPROX 3 SECS THEN TURNED OFF. ALL PARAMETERS REMAINED NORMAL, NO FIRE NOTED. REMOVED AND REPLACED FIRE DETECTING CONTROL UNIT IAW AMM 26-11-10-02 PN OFF/ON 899052-02 SN OFF 0788 SN ON 0485, OPS CHECK OK.