As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ORD - INFLIGHT DTW-DFW. CREW REPORTED UNABLE TO PRESSURIZE CABIN DURING CLIMBOUT. SELECTED CABIN ALT CNTRL LEVER TO MANUAL AND MANUALLY CLOSED THE OUTFLOW VALVE. THE CABIN CONTINUED TO CLIMB AND INITIATED DESCENT TO 10,000. EMERGENCY DECLARED FLIGHT DIVERTED ORD LANDED WITHOUT INCIDENT. AIRCRAFT REMOVED FROM SERVICE. REPLACED BLOWN DUCT IN AFT STAIRS. SYSTEM GROUND CHECK NORMAL OPERATION.