As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
SLC - FLT 202 - AIRCRAFT WOULD NOT PRESSURIZE AFTER TAKEOFF (AUTO, STANDBY, OR MANUAL). COULD NOT CONTROL OUTFLOW VALVE. RETURNED FOR LANDING AT DEN WITHOUT INCIDENT. PERFORMED SYSTEM TEST PER MM 21-31-0A. RAN ENGINES AND PRESSURIZED AIRCRAFT. OPERATION CHECKED NORMAL. AIRCRAFT WAS RETURNED TO SERVICE. (X)