If the display function does not work, replace the meter unit.

Check 3-6: Neutral Indicator Light (LED) Inspection
Meter Unit Circuit (ZX1000J Model)Daily Checks
Check the following items each day before you ride. The time required is
minimal,
and habitual performance of these checks will help ensure you a safe, reliable
ride.
If any irregularities are found during these checks, refer to the Maintenance
and
Adjustment chapter or see your dealer fo ...
Throttle Grip and Cables
Free Play Inspection
Refer to the Throttle Control System Inspection in the Periodic
Maintenance chapter.
Free Play Adjustment
Refer to the Throttle Control System Inspection in the Periodic
Maintenance chapter.
Cable Installation
Install the throttle cables in accordance with the Cable,
...
Idle Speed Control Valve Actuator Resistance Inspection
Turn the ignition switch to OFF.
Remove the air cleaner housing (see Air Cleaner Housing
Removal in the Fuel System (DFI) chapter).
Disconnect the idle speed control valve actuator connector
[A].
Connect a digital meter to the idle speed control valve
actuator connector [A]
...