As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ON CLIMB OUT FROM DENVER, CENTENNIAL, (KAPA), THE AIRPLANE WOULD NOT PRESSURIZE. THE CREW ELECTED TO RETURN TO THE POINT OF DEPARTURE. MAINTENANCE WAS SUMMONED. IT WAS DETERMINED THAT THE PRESSURIZATION CONTROLLER HAD FAILED. AN OVERHAULED PRESSURIZATION CONTROLLER WAS INSTALLED AND WAS OPERATIONALLY TESTED ON THE GROUND. AN EVALUATION FLIGHT WAS DONE, AND THE PRESSURIZATION SYSTEM WAS FOUND TO OPERATE SATISFACTORY. AIRCRAFT WAS RETURNED TO SERVICE.