As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
WHILE PERFORMING FIRE LOOP TEST FOUND NR 1 ENG 'T' HANDLE LIGHT NOT ILLUMINATED. GROUNDED - YES. REMOVED AND REPLACED MW0326 ENGINE CORE LOOP B FIRE DETECTION HARNESS. AS A PRECAUTION, REMOVED AND REPLACED LOWER CORE FIRE DETECTOR ASSY. REVERSED ALT DEACTIVATIONS.