As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PHX - DURING CRUISE AT FL330, THE CREW RECEIVED A CABIN PRESSURIZATION WARNING HORN. THE CREW SWITCHED TO MANUAL MODE AND THE CABIN CONTINUED TO CLIMB. THE CREW DECLARED AN EMERGENCY AND DESCENDED TO FL 120. THE CREW DIVERTED TO TUS. MX REMOVED AND REPLACED THE CABIN OUTFLOW VALVE PER T/C R6A21001. OPS CHECK WAS GOOD.