As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
APU FAULT LIGHT ILLUMINATED ON APU START. GROUNDED - YES. UPON INSP FOUND APU INLET DOOR 1/3 OPEN WITHOUT A/C EXT PWR. AFTER SUPPLYING EXT PWR NO STATUS MSG SHOWN FOR APU FAULTS. STARTED APU MULTIPLE TIMES WITHOUT APU STATUS MSG OR FAULTS. INLET DOOR OPERATES AS INTENDED. SUSPECT IMPROPER APU SHUTDOWN PROCEDURE PREVIOUSLY INDUCED FAULT. RAN APU BITE PER B737-9 AMM 49-61-00 NO FAULTS FOUND.