As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
APU PNEUMATIC INOP (AUXILIARY POWER UNIT, PNEUMATIC FUNCTION). PERFORMED BITE CHECK OF SYSTEM PER AMM 49-61-05. NO FAULTS NOTED. APU START 1ST ATTEMPT. CB BREAKER S-23 C VALVE VERIFIED IN OFF POSITIONS PER 36-11-04. REMOVED AND REPLACED SURGE CONTROL VALVE IAW AMM 49-53-01. OPS CHECK NORMAL. NO AUTO SHUTDOWN. PERFORMED APU BITE IAW AMM 49-61-05. NO FAULTS NOTED. THIS CLEARS DMI 130515. PLACARDS REMOVED. MCC NOTIFIED.