As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AFTER ALL ENGINES START, STATUS MESSAGE FOR APU FIRE LOOP 1. REPLACED THE APU NR 1 FIRE DETECTION LOOP CARD, M685. FOUND INSULATION RESISTANCE CHECK FLUCTUATING ON UPPER NR 1 LOOP. PERFORMED RESISTANCE AND WIRING CHECKS IAW WDM 26-15-11. REPLACED THE UPPER NR 1 FIRE DETECTION LOOP IAW AMM 26-15-02. OPS AND LEAK CHECKED GOOD.