As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
WHILE ACCOMPLISHING TC N8420000, FOUND DAMAGE ON #1 ENGINE CORE FIRE DETECTOR HARNESS MW0325. GROUNDED - YES. REMOVED AND REPLACED #1 ENGINE CORE FIRE DETECTOR HARNESS MW0325. INSTALLATION TEST ACCOMPLISHED WITH NO FAULTS NOTED, REF B737 - 900 AMM 26-11-02. OPENED, TAGGED, AND RESET THREE CIRCUIT BREAKERS.