What was found
IN CRUISE L-FMC FAILURE AS INDICATED BY #1 CDU BLANKING #2 CDU REVERTING TO MENU PAGE WITH NO FMC ANNUNCIATION AND "VTK" DISPLAYED ON CAPTAIN'S MAP DISPLAY ACCOMPANIED BY DISAPPEARANCE OF MAP DATA. LNAV AND VNAV DISENGAGED. SELF -RECOVERED IN APPROXIMATELY 30 SECONDS. PRIOR TO COMMENCEMENT OF QRH PROCEDURE. GROUNDED - YES. REBOOTED R&L-FMC REF B737-900 AMM 34-61-00-810-807 & NORM OPS RESTORED REF B737-900 FIM TASK 34-61 TASK 836. OPS CK OK REF AMM 34-61-00-710-801.