As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FLT#1621, LHR-BOS. (ETOPS) 'ENG 1 FIRE LOOP "A" FAULT; PERFORMED FIM TASK 26-12-00-810-803-A FOUND AGB CORE LOOP A SHORTED TO GROUND. REMOVED AND REPLACED AGB CORE LOOP A 4002WD1 IAW AMM 26-12-17-000-802. OPS CHECK GOOD AT THIS TIME.' (SUPPLEMENTAL INFORMATION ADDED TO ENGINE INFORMATION)