As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FLT#2677, BOS-LAS. (ETOPS) 'ENG 2 FIRE LOOP B FAULT ( ENGINE FIRE DETECTION SYSTEMS 2) LOOP B ). REMOVED AND REPLACED ENG 2 LOOP B PYLON DETECTOR (4WD2) PER AMM 26-12-16. OPS CHECK NORMAL MESSAGE EXTINGUISHED. THIS CLEARS MDDR 531326. MX-4 UPDATED. PLACARD REMOVED.