As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AT FL250 ALTITUDE WARNING HORN WENT OFF WITH CABIN ALT AT 12,000 FT. CREW WENT ON 02, OUTFLOW VALVE SHOWED CLOSED. CARGO VALVE CLOSED, LT PACK OFF, DUE TO PREVIOUS WRITE UP. FOUND LT PACK VALVE INOP AND LT ACM NOT TURNING. REPLACED LT PACK VALVE AND ACM CKS OK.