As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PRESSURIZATION FLOW LIGHT ILLUMINATED DURING FLIGHT. CABIN ALTITUDE SLOWLY INCREASED FROM 4 TO 6.0 AT FLIGHT LEVEL 250. DECLARED EMERGENCY AND LANDED DFW WITHOUT INCIDENT. REPLACED FLOW CONTROL VALVE. SYSTEM GROUND CHECKED NORMAL OPERATION.