As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING TAXI FLIGHT CREW REPORTED APU FIRE WARNING SYSTEM WARNING LIGHT ILLUMINATED. DISCHARGED SQUIB. MAINTENANCE CONDUCTED INSPECTION OF APU COMPARTMENT AND FOUND NO EVIDENCE OF FIRE. PLACARD SYSTEM PER MEL 26-07. AN ADDENDUM WILL BE ISSUED WHEN REPAIR IS ACCOMPLISHED. RAN APU SEVERAL HOURS AND PERFORMED OPERATIONAL CHECK OF APU FIRE DETECTION SYSTEM PER MM 26-15-00, WITH NO DISCREPANCIES NOTED.