As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DECLARED EMERGENCY. DURING APU START, APU FIRE WARNING LIGHT ILLUMINATED. APU FIRE HANDLE PULLED. NO OTHER IND OF APU FIRE. INSPECTED APU AREA FOR EVIDENCE OF FIRE. NO DEFECT NOTED. DEFERRED APU SYS. DURING RON IN HOU, FOUND APU TAILPIPE HARNESS AND SENSOR DEFECTIVE. REMOVED AND REPLACED BOTH PER MM. OPS CK GOOD. APU FIRE BOTTLE REPLACED.