As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
APU FIRE WARNING ON GROUND. APU FIRE BOTTLE DISCHARGED. MAINTENANCE FOUND NO EVIDENCE OF ACTUAL FIRE. REPLACED FIRE DETECTOR CARD A21 FOR LOOP-A AND APU FAULT CARD A22. FIRE DETECTOR LOOP-B INOPERATIVE. PLACED APU ON MEL. REPLACED FIRE BOTTLE.