What was found
OKC - FLIGHT 2176, THE CREW REPORTED THAT PRESSURIZATION FAILED ON DESCENT INTO OKC. THE AIRCRAFT LANDED IN OKC WITHOUT INCIDENT WHERE MAINTENANCE PLACED PRESSURIZATION ON MEL 21-30-00/3 CAT C, AND THE AIRCRAFT WAS APPROVED FOR RETURN TO SERVICE. THE AIRCRAFT TON'D AT IAH WHERE MAINTENANCE REMOVED AND REPLACED THE DIGITAL CONTROLLER, OPERATIONALLY TESTED WITH NO DEFECTS, REMOVED THE MEL, AND THE AIRCRAFT WAS APPROVED FOR RETURN TO SERVICE.