What was found
EN ROUTE, CREW REPORTED THAT AT FL 340 AUTO STANDBY DID NOT HOLD ALTITUDE. CREW DESCENDED TO FL 100. MASKS DID NOT DEPLOY DUE TO GRADUAL LOSS OF PRESSURIZATION. CREW DIVERTED TO ICT AND LANDED WITHOUT FURTHER EVENT. MAINT PERFORMED LINE MAINT PRESSURIZATION INTEGRITY CHECK IAW AWA TASK CARD F1B21006 AND FOUND TO BE WITHIN LIMITS. PERFORMED CABIN PRESSURIZATION CONTROL OPS TESTS AND OPERATION WAS NORMAL. AC WAS FERRIED. MAINT INSPECTED OUTFLOW VALVE GASKET HEATER IAW A6A21001. OPERATIONAL CHECKS WERE GOOD. MAINT REPLACED THE CABIN PRESSURE CONTROLLER FOR PRECAUTIONARY PURPOSES. OPS CHECKS WERE GOOD IAW AWA TASK CARD F1B21001. WILL BE SUBMITTED UPON RECEIPT OF VENDOR TEAR DOWN REPORT.