What was found
ON CLIMBOUT, ABOUT 1000 ' MSL, VNAV DISCONNECTED AND WOULD NOT RE- ENGAGE. FMC CLIMB AND CRZ PAGE SPEEDS BLANKED OUT. AFTER 60-90 SECONDS, SPEEDS RE- POPULATED ON CLB & CRZ PAGES AND VNAV WAS ENGAGEABLE. VNAV WORKED NORMALLY FOR THE REST OF FLIGHT, INCLUDING RNAV RNP APPROACH. GROUNDED - YES. PERFORMED FMC BITE CHECK OPS CHECK GOOD REF B737-900 FIM 34-61 TASK 801. DFCS BITE TEST CHECKS GOOD REF TASK 22-11-00-740-815. PERFORMED FIM 34-61 TASK 804 "CONTROL DISPLAY UNIT BLANKS" NO DEFECTS NOTED.