What was found
AFTER LANDING "FMC" INDICATION GONE FROM FMC MENU. RETURNS BRIEFLY AND THEN GOES AWAY. AFFECTING BOTH FMC'S. GROUNDED - YES. UNABLE TO DUPLICATE DEFECT: FMCS BITE SHOWED EACH FMC RECORDED THE SAME FAULTS FOR THE OTHER FMC ON LEG 2: "GENERAL DATA SYNC ERROR" AND "FCC DATA SYNC ERROR". PERFORMED T/S PER B737-800 FIM 34-61 TASK 836 - INITIAL EVALUATION DID NOT CONFIRM FAULT. PERFORMED FMCS OPERATIONAL TEST PER B737-800 AMM 34-61-00-710-801 - ALL TESTS PASS.