What was found
DURING CRUISE, THE OUTFLOW VALVE FLUCTUATED FROM +1500 FEET PER MINUTE TO -1000 FEET PER MINUTE NUMEROUS TIMES THROUGHOUT FLIGHT. ACFT GROUNDED. UNABLE TO DUPLICATE DEFECT. BITE OF NR 1 AND 2 CABIN PRESSURE CONTROLLERS IAW FIM 21-31 TASK 801, SHOWED NO FAULT ON EITHER CONTROLLER AND SYSTEM TEST PASSED WITH NO FAULTS. BITE OF LEFT AND RIGHT PACK FLOW TEMPERATURE CONTROLLERS IAW FIM 21-62 TASK 801, SHOWED NO FAULTS. BITE OF LEFT AND RIGHT ADIRU IAW FIM 34-21 TASK 801, SHOWED NO FAULTS. PERFORMED PRESSURIZATION SYSTEM GROUND TEST IAW AMM 21-31-00-700-802 AND PRESSURIZATION SYSTEM MANUAL MODE TEST IAW AMM 21-31-00-710-801 ALL TESTS PASS. OUTFLOW VALVE OPERATION WAS SMOOTH AND NORMAL DURING TEST. REMOVED AND REPLACED CABIN PRESSURE CONTROL MODULE IAW AMM 21-31-02-000-801 AND 21-31-02-400-801. PERFORMED PRESSURIZATION SYSTEM GROUND TEST IAW AMM 21-31-00-700-802 AND PRESSURIZATION SYSTEM MANUAL MODE TEST IAW AMM 21-31-00-710-801. ALL TESTS PASSED.