As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FLT 9225 - CLT - FALSE FIRE WARNING - DURING CRUISE AT FL390 DURING LIGHT TURBULENCE, MASTER CAUTION AND FIRE BELL RANG FOR 3 RINGS AND WENT SILENT. FULL SYSTEMS CHECK AND FIRE/SMOKE CHECK ACCOMPLISHED. NO FAULTS OR ECAMS INDICATED AND NO REOCCURRENCE OF EVENT DURING FLIGHT. MAINTENANCE FOUND LAST LEG FAULT "CK FDU ENG 1 SUPPLY". REPLACED NR 1 ENGINE FIRE DETECTION UNIT 2WD1 IAW AIRBUS MAINTENANCE MANUAL 26-12-34.