If the oil leakage is found on it, replace the steering damper with a new one (see Steering Damper Removal/ Installation in the Steering chapter).

ZX1000JD/KD [B]

Steering Stem Bearing LubricationESD (Electronic Steering Damper) ECU Error (Service Code E3b, ZX1000JD/KD)
If this service code appears, check that the following parts
are correctly.
Crankshaft Sensor
Gear Position Switch
Starter Lockout Switch
Main Throttle Sensor
Rear Wheel Rotation Sensor
If these parts are normal, check the ESD ECU for its
ground and power supply (see ESD ECU Power Supply
...
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.
...
Rear Master Cylinder Removal
Unscrew the brake hose banjo bolt [A] and remove the
brake hose (see Brake Hose and Pipe Replacement in
the Periodic Maintenance chapter).
Remove:
Rear Master Cylinder Mounting Bolts [B]
Foot Guard [C]
Screw and Stopper [D]
Bolt [E]
Front Footpeg Bracket Bolts [F]
Cable Guide [G ...