Replace it if necessary.

Inner Tube Inspection
Spring Tension InspectionPiston Wear Inspection
Measure the outside diameter [A] of each piston 5 mm
(0.20 in.) [B] up from the bottom of the piston at a right
angle to the direction of the piston pin.
If the measurement is under service limit, replace the piston.
Piston Diameter
Standard: 75.959 75.974 mm
(2.9905 2.9911 in.)
...
Camshaft Removal
Remove:
Cylinder Head Cover (see Cylinder Head Cover Removal)
Crankshaft Sensor Cover (see Crankshaft Sensor Removal
in the Electrical System chapter)
Using a wrench on the timing rotor bolt [A], turn the crankshaft
clockwise until the line [B] (TDC mark for #1,4 pistons)
on the timin ...
Air Switching Valve Removal
NOTICE
Never drop the air switching valve especially on a
hard surface. Such a shock to the air switching
valve can damaged it.
Remove the air cleaner housing (see Air Cleaner Housing
Removal in the Fuel System (DFI) chapter).
Disconnect the connector [A].
Disconnect the hoses [B] from ...