What was found
AIR RETURN TO OMA DUE TO AIRCRAFT NOT PRESSURIZING. FLIGHT LANDED SAFELY AND NOT OVERWEIGHT. INTERROGATED MDC AND FOUND NO CURRENT FAULTS OR HISTORICAL FAULT CODES POSTED ON THE PREV FLT LEG, INSPECTED OUTFLOW VALVE FOR FOD INGESTION NO FOD FOUND IN VALVE, PERFORMED OPERATIONAL CHECK OF THE CABIN PRESSURIZATION SYSTEM IN AUTO AND MANUAL MODES IAW CRJ900 AMM21-31-00-710-801/802, AND FUNCTIONAL TEST OF THE OUT FLOW VALVE IAW CRJ900 AMM21-31-01-720-801-A01 SYSTEM OPS CHECKS GOOD AT THIS TIME AIRCRAFT OK FOR SERVICE.