What was found
AT 3000' MSL W/LNAV AND VNAV ENGAGED, FO'S ND DISPLAYED VTK AND PFD DISPLAYED LDG ALT FLAG AND LNAV AND VNAV DISENGAGED ABOUT A MINUTE LATER ALL FLAGS DISAPPEARED AND FO MAP DISPLAY WAS NORMAL. GROUNDED - YES. AT TECH SERVICES REQUEST, REMOVED AND REPLACED #1 FMC WITH P/N: 176200-01-01 IAW B737-900 AMM 34-61-02-000/400-801. VERIFIED CORRECT OPS SW PRESENT, AND SUBSEQUENTLY CROSSLOADED FROM #2 FMC ALL RELEVANT SW IAW AMM 34-61-00-470-806. LOADED NEW NAV DB INTO #1 FMC AND CROSSLOADED TO #2 FMC. REF TC N8234000. PERFORMED PERF FACTORS ADJUSTMENT IAW AMM 34-61-00-800-801. PERFORMED OPS TEST IAW 34-61-00-710-801, CHECKS GOOD.