What was found
AT FL360 AN IMMEDIATE LOSS OF CABIN PRESSURIZATION WAS EXPERIENCED. CABIN PRESSURIZATION IMMEDIATELY WENT ABOVE 10,000 FEET. EMERGENCY DESCENT WAS INITIATED TO 15,000 FEET. AFTER LEVEL OFF AUTOMATIC CABIN PRESSURE CONTROLLER WAS FLASHING A CODE OF AO16. AFTER THE MANUAL MODE OF THE CABIN PRESSURIZATION SYSTEM WAS SELECTED, CABIN PRESSURIZATION BECAME CONTROLLABLE. NO OTHER MALFUNCTIONS OF THE CABIN PRESSURIZATION SYSTEM WERE NOTED. TROUBLESHOT PRESS SYSTEM FOUND PRESS CONTROLLER FAILED. REMOVED & REPLACED AS INSPECTED SERVICEABLE UNIT PER F2000 M/M CH 21-302 AND RAN TO OPS CHECK GOOD.