As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PIT - FLIGHT WAS HOLDING FOR LANDING AT PHL WHEN BOTH AUTO PRESSURE CONTROLLERS FAILED AND CABIN ALTITUDE BEGAN TO CLIMB. CREW DECLARED AN EMERGENCY. FLIGHT LANDED WITH NO FURTHER INCIDENT. MAINTENANCE REPLACED THE LEFT PACK CONTROL VALVE DUE TO LOW FLOW. (M)