As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DFW - CREW REPORTED LEFT PACK WAS UNABLE TO PRESSURIZE CABIN WITH RIGHT PACK ON DEFERRAL. EMERGENCY DECLARED FLIGHT RETURNED DFW LANDED WITHOUT INCIDENT. AIRCRAFT REMOVED FROM SERVICE. REPLACED LEFT ANTI ICE VALVE AND RIGHT PACK TEMPERATURE CONTROLLER (MPN 60714622). SYSTEM GROUND CHECK NORMAL OPERATION.