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

Check 3-6: Neutral Indicator Light (LED) Inspection
Meter Unit Circuit (ZX1000J Model)Rear Wheel Installation
Apply high-temperature grease to the grease seal lips.
Fit the collars on the both sides of the hub.
Left Side Collar [A]
Right Side Collar [B] (with Flange)
Engage the drive chain with the rear sprocket.
Install the caliper bracket [A] onto the stopper [B] of the
swingarm.
...
Terminal Numbers of ECU Connectors
1. Subthrottle Valve Actuator: Y/BK
2. Subthrottle Valve Actuator: BK/O
3. Unused
4. Front Wheel Rotation Sensor Signal: G/Y
5. Unused
6. Starter Lockout Switch: R/G
7. Gear Position Switch: G/R
8. Crankshaft Sensor (–): BK
9. Power Supply to Sensors: BL
10. Unused
11. Intake Air Pre ...
Lights and Switches Operation Inspection
First Step
Set the gear position in the neutral position.
Turn the ignition switch to ON.
The following lights should go on according to below table.
If the following light does not go on, inspect the meter
unit (see Meter Unit Inspection in the Electrical System
chapter).
...