As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PDX- FLIGHT 2533, AFTER APU SHUTDOWN RECEIVED A APU SOV OPEN MESSAGE. RETURNED TO THE GATE. MAINTENANCE CYCLED THE APU, NO DEFECTS NOTED. NO FAULTS FOUND IN THE MAINTENANCE DATA COMPUTER. AIRCRAFT RETURNED TO SERVICE. NO PARTS REPLACED.