As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DEN - CREW REPORTED AIRCRAFT FAILED TO PRESSURIZE. FLIGHT RETURNED DEN LANDED WITHOUT INCIDENT. PLACARD NUMBER 2 AUTO PRESSURE CONTROLLER INOPERATIVE. FLIGHT CONTINUED ON TO DESTINATION. REPLACED NUMBER 2 AUTO PRESSURE CONTROLLER AT SEA ON 08/27/2011. SYSTEM GROUND CHECK NORMAL OPERATION.