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

Check 3-6: Neutral Indicator Light (LED) Inspection
Meter Unit Circuit (ZX1000J Model)Windshield
Windshield Removal
Remove:
Bolts [A] and Washers
Windshield [B]
Windshield Installation
Be sure to install the wellnuts [A] and the washers.
Tighten:
Torque - Windshield Mounting Bolts: 1.2 N·m (0.12 kgf·m,
11 in·lb)
...
Camshaft Installation
NOTE
The exhaust camshaft has a 1001 EX mark [A] and the
intake camshaft has a 3154 IN mark [B]. Be careful not
to mix up these shafts.
Install the camshaft sprockets as shown in the figure.
#4 Cam Positions [A]
Intake Camshaft Sprocket [B]
Exhaust Camshaft Sprocket [C]
The int ...
Mode-switching
Depress the S-KTRC button on the left handlebar switch
to change the mode. The mode can be changed only when
the throttle grip is closed completely.
The S-KTRC OFF can be selected only when the motorcycle
is at a stop. Changing to mode 1 from S-KTRC OFF
is possible while riding.
NOTE
...