What was found
CAPTAINS MCDU SCREEN BLANKED, WARNING LIGHT CAME ON, AND BIT MESSAGE DISPLAYED ON SCREEN. SEQUENCED AT LEAST 10 CYCLES. NO ASSOCIATED MAP OR VTK WARNING ON CDU'S. GROUNDED - YES. REMOVED, REPLACED, AND TESTED CAPTAIN'S MCDU PER B737-800 MM 34-61-01-000-802 / AMM 34-61-01-400-802 - OPS NORMAL.