As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING A FIRE DETECTION TEST, THE AFT ANNUNCIATOR LIGHT DID NOT COME ON. LIGHT COMES ON WITH MASTER LIGHTS TEST. ACFT GROUNDED. VERIFIED DISCREPANCY IAW FIM 26-16 TASK 801, FOUND THE AFT CARGO FIRE DETECTOR B3, M2247, INOPERATIVE. REPLACED THE FIRE DETECTOR IAW AMM 26-16-01. GROUND VERIFICATION SUCCESSFUL IAW AMM 26-16-00.