As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
THE AUXILIARY POWER UNIT FIRE BOTTLE DISCHARGED BY THE FLIGHT CREW . *S/D* THE SHORTED M717 DETECTOR CAUSED A FALSE FIRE INDICATION. REPLACED THE M717 LOOP AND THE AUXILIARY POWER UNIT FIRE BOTTLE. REPLACED THE M515 LOOP AS A PRECAUTION.