As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
CABIN ALT WARNING HORN SOUNDED AT 15;700 FT. COMPLIED WITH CONDITIONAL INSP 05-51-91. CABIN PRESSURE LEAK TEST. DISCOVERED BOTH ENGINE BLEED SWITCHES IN THE OFF POSTION WHEN ACFT RETURNED TO GATE. AHM CONFIRMED NO DUCT PRESSURE FOR ENTIRETY OF FLIGHT. SWITCH POSITION CONFIRMED WITH FDR DOWNLOAD AMM 31-31-00. NOT A DECOMPRESSION EVENT; ACFT NEVER PRESSURIZED.