As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
CAPT NAV DISPLAY HAD VTK FLAG LNAV DISAGREED AND LEFT FMC BLANKED AT CRUISE. SWITCHED TO USING RT FMC AND AUTOPILOT WITHIN 5 MINS LEFT FMC RESTORED. GROUNDED - YES. FOUND L FMC DATE RATE FAULT LOGGED BY R FMC. CW RESET PER B737-900 FIM 34-61 TASK 807. OPS NORMAL.