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

Check 3-6: Neutral Indicator Light (LED) Inspection
Meter Unit Circuit (ZX1000J Model)Hoses and Pipes
Hose Installation
Install the hoses and pipes, being careful to follow bending
direction. Avoid sharp bending, kinking, flattening or
twisting.
Run the hoses (see Cable, Wire, and Hose Routing section
in the Appendix chapter).
Install the clamp [A] as near as possible to the hose end
...
Front Fork Removal (Each Fork Leg)
Loosen the front fork top plug [A] beforehand if the fork
leg is to be disassembled.
Special Tool - Top Plug Wrench (45 mm) [B]: 57001-1741
NOTE
Loosen the top plug after loosening the handlebar
clamp bolt [C] and upper front fork clamp bolt [D].
Remove:
Upper Fairing Assembly (see Up ...
Battery Removal
Turn off the ignition switch.
Remove the front seat (see Front Seat Removal in the
Frame chapter).
Slide the red cap [A].
Disconnect the negative (–) cable [B] and then positive
(+) cable [C].
NOTICE
Be sure to disconnect the negative (–) cable first.
Remove the band [D] ...