As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
CAPTAIN REPORTED DURING A TRANSIT CHECK, THE FIRE DETECTOR OF LOOPS A & B WITH FAULT LIGHT ON LEFT ENGINE. MAINTENANCE PERSONNEL PERFORMED AN INSPECTION IAW AMM 26-11-00 CONFIRMING FAILURE. THE FIRE DETECTOR ASSY UPPER WAS REPLACED IAW AMM 26-11-01, TESTED CORRECT.