As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
APU SHUTDOWN WITH A FAULT LIGHT DURING PREFLIGHT. PERFORMED AN INSPECTION OF THE APU AIR SUPPLY VALVE IAW AMM 36-11-11, FOUND IT FAULTY, REMOVED AND REPLACED THE CHECK VALVE IAW AMM 36-11-11. RAN APU WILL FULL LOAD FOR 30 MINUTES NO FAULTS NOTED.