What was found
PHX - DIVERSION - FLT 0778 - AFTER TAKEOFF FROM LAS EN ROUTE FOR BWI CENTER IRS ALIGN LIGHT BEGAN FLASHING WITH FLIGHT MANAGEMENT COMPUTER (FMC) MESSAGES -IRS MOTION & RESET IRS POSITION-. WITH V/S ON FL/CH SELECTED V/S MODE SELECTED ITSELF AND V-NAV WOULD NOT DESELECT. RT CONTROL DISPLAY UNIT FROZE UP FOR A WHILE WITH STANDBY FMC MESSAGE. DIVERTED TO PHX AND LANDED WITHOUT FURTHER EVENT. MAINTENANCE REMOVED AND REPLACED CENTER INERTIAL REFERENCE UNIT IAW 34-21-01, OPERATIONAL CHECK WAS GOOD. *S/D* VENDORS FUNCTIONAL TEST OF INERTIAL REFERENCE UNIT S/N 123401 WAS NO FAULT FOUND. PERFORMED 24 HOUR BURN IN AND PERFORMANCE TEST, TESTS GOOD IAW CMM 34-21-13 REV 9.