As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
NR 1 ENGINE FIRE DETECTION TEST FAILS IN NORMAL AND LOOP A POSITION. ACFT GROUNDED. REPLACED THE NR 1 ENGINE RT CORE , LT CORE & TWO WIRE ON EACH LUG, GROUND FUNCTIONAL CHECKED NORMAL IAW AMM 26-11-00-710-801 & ENGINE RUN-UP IDLE POWER FOR 15 MINUTES, OPS CHECKED NORMAL.