If a master cylinder or piston shows any damage, replace them.

If a cup is worn, damaged softened (rotted), or swollen, the piston assembly should be replaced to renew the cups.
If fluid leakage is noted at the brake lever, the piston assembly should be replaced to renew the cups.
If they are damaged, replace them.
If the springs are damaged, replace them.
If the relief port becomes plugged, the brake pads will drag on the disc. Blow the ports clean with compressed air.
Front Master Cylinder [I] Rear Master Cylinder [J]

Rear Master Cylinder Installation
Brake DiscExploded View
AL: Tighten the two clamp bolts alternately two times to ensure even
tightening torque.
G: Apply grease.
R: Replacement Parts
G: Apply grease.
L: Apply a non-permanent locking agent.
R: Replacement Parts
Specifications
...
ESD Actuator Input Voltage Inspection
NOTE
Be sure the battery is fully charged.
Turn the ignition switch to OFF.
Disconnect the ESD actuator connector and connect a
suitable measuring leads [A] between these connectors
as shown.
Main Harness [B]
ESD Actuator [C]
Connect the peak voltage adapter [D] and a digital ...
Crankshaft Sensor Inspection
Disconnect the crankshaft sensor lead connector (see
Crankshaft Sensor Removal).
Set the hand tester [A] to the × 10 Ω range and connect it
to the crankshaft sensor lead connector [B].
Special Tool - Hand Tester: 57001-1394
Crankshaft Sensor Resistance
Connections:
Meter (+ ...