As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING CLIMB THRU RECEIVED LT ENG FIRE DETECT MSG ON EICAS. RETURNED WITH NO PROBLEM. ACCESS EXTERNAL AND INTERNAL BYPASS DUCT ON LT ENGINE VISUALLY INSPECTED INTERNAL ZONE 2 FIRE DETECTOR ALSO EXTERNAL ZONE 1 FIRE DETECTOR. NO DEFECTS FOUND. REMOVED LOWER PYLON PANELS FOR ACCESS TO CONNECTOR TROUBLESHOT SYSTEM AND FOUND ZONE 2 OVERHEAT LOOP TO BE BAD. REPLACED ZONE 2 FIRE LOOP, OPS CHECKS GOOD. ALL WORK DONE IAW MM 21-10-10.