What was found
ON A FLIGHT, THE FLIGHT CREW NOTICED THAT THE PRESSURIZATION SYSTEM WAS NOT INCREASING CABIN PRESSURE AT A RATE TYPICAL TO NORMAL AIRCRAFT OPERATION. AT 17,000 FT, WITH A CABIN ALTITUDE LOWER THAN THEY WERE USE TO SEEING, THE FLIGHT CREW DECIDED TO RETURN, LANDED WITHOUT INCIDENT. PRESSURIZATION CONTROL MODULE SUSPECTED TO BE FAULTY.