As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT HAD APU FIRE INDICATION ON FINAL APPROACH. INSPECTED APU OVERHEAT DETECTION SYSTEM AND FOUND APU TAILPIPE OVERHEAT DETECTOR LOOP SHORTED. ALL OTHER LOOPS CHECKED OK. REPLACED APU OVERHEAT DETECTOR LOOP. APU FIRE DETECTION SYSTEM WAS RESTORED TO NORMAL CONDITION.