As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
TROUBLESHOOTING RECOMMENDATIONS FOR HISTORY OF #2 ENGINE B LOOP NOT TESTING PROPERLY AND CAUSING DELAYS. GROUNDED - YES. REPLACED CORE FIRE DETECTION HARNESS MW0326 ON #2 ENGINE REF. B737-800 AMM 26-11-02. REPLACED FAN FIRE DETECTION HARNESS MW0316 ON #2 ENG REF. AMM 26-11-02. OPS CHECKS GOOD.