As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
CREW REPORTED APU AUTO SHUT DOWN AND FIRE WARNING. FLIGHT CREW DISCHARGED THE FIRE BOTTLE. SUPPLEMENTAL DATA UPDATE: REPLACED APU FIRE BOTTLE AND SQUIBB PER MM 26-22-02. RAN APU AND CHECKED FOR PNEUMATIC LEAKS, NO LEAKS FOUND. APU RAN FOR SEVERAL HOURS WITH NO SHUT DOWN. VISUALLY CHECKED BOTH UPPER AND LOWER DETECTOR LOOPS AND CLEANED CONNECTORS. REPLACED CARD M10400, OPERATIONAL CHECK NORMAL.