If they appear damaged or deteriorated, replace them.

Balancer Adjustment
Torque LimiterTachometer
The tachometer shows the engine
speed in revolutions per minute (r/min,
rpm).
On the right side of the tachometer
face is a portion called the “red zone”.
Engine r/min (rpm) in the red zone is
above maximum recommended engine
speed and is also above the range for
good performance.
...
Precautions
There are a number of important precautions that are
musts when servicing electrical systems. Learn and observe
all the rules below.
Do not reverse the battery cable connections. This will
burn out the diodes on the electrical parts.
Always check battery condition before condemning other
...
Rear Wheel Rotation Sensor Wiring Inspection (Service Code b 45)
Disconnect the rear wheel rotation sensor lead connector
[A] (see Rear Wheel Rotation Sensor Removal in the
Brakes chapter).
Disconnect the KIBS hydraulic unit lead connector (see
KIBS Hydraulic Unit Removal in the Brakes chapter).
Check the wiring continuity of the G lead and R ...