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

Check 3-6: Neutral Indicator Light (LED) Inspection
Meter Unit Circuit (ZX1000J Model)Serial number locations
The engine and frame serial numbers are used to register the motorcycle.
They
are the only means of identifying your particular machine from others of the
same
model type. These serial numbers may be needed by your dealer when ordering
parts. In the event of theft, the investigating authoriti ...
Bolts, Nuts and Fasteners Tightness Inspection
Check the tightness of the bolts and nuts listed here. Also,
check to see that each cotter pin is in place and in good
condition.
NOTE
For the engine fasteners, check the tightness of them
when the engine is cold (at room temperature).
If there are loose fasteners, retighten them to ...
Intake Air Temperature Sensor Output Voltage Inspection
NOTE
Be sure the battery is fully charged.
Turn the ignition switch to OFF.
Remove the fuel tank (see Fuel Tank Removal in the Fuel
System (DFI) chapter).
Disconnect the intake air temperature sensor connector
and connect the measuring adapter [A] between these
connectors as shown in ...