As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
#2 ENGINE FIRE DETECTION LOOP B HAS A FAULT LOOP A DOES NOT SHOW A FAULT. GROUNDED - YES. REMOVED AND REPLACED NR 2 ENGINE MW0326 CORE FIRE DETECTOR HARNESS REF B737-900 AMM 26-11-02. ACCOMPLISHED ENGINE FIRE DETECTION OPS CHECK REF AMM 26-11-00-710-801 ALL TEST PASS. GROUND VERIFICATION TEST SUCCESSFUL.