What was found
DUAL FMC FAILURE ENROUTE (NOT ASSOCIATED W/LOADING ARCH PRIOR TO DESCENT WIND UPLINK). RESET ON ITS OWN AFTER APPROX 30 SECONDS. INDICATIONS: "VTK" ON CA ND, BOTH FMCDU FAIL, LOSS OF LNAV & VNAV. MAP INFORMATION REMAINED ON BOTH ND. GROUNDED - YES. NO CURRENT FAULTS. PERFORMED LEFT AND RIGHT OPS TEST PER B737-9 AMM 34-61-00-710-801 NO DEFECTS NOTED.