Remove the harness holder (A).

Check the PCV valve (A), the hoses (B), the pipe (C), and the connections for leaks or restrictions.

At idle, make sure there is a clicking sound from the PCV valve when the hose between the PCV valve and the intake manifold is lightly pinched (A) with your fingers or pliers.
If there is no clicking sound, check the PCV valve washer for cracks or damage. If the washer is OK, replace the PCV valve and recheck.

Output Shaft (Countershaft) Speed Sensor Replacement (A/T)
Remove the air cleaner assembly.
Disconnect the output shaft (countershaft) speed sensor connector, and
remove the output shaft (countershaft) speed sensor (A).
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Secondary HO2S Replacement
Special Tools Required
O2 Sensor Wrench Snap-on S6176 or equivalent, commercially available
Disconnect the secondary HO2S connector (A).
Raise the vehicle on a lift.
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Removal
Do the battery terminal disconnection procedure.
Remove the drive belt.
Remove the intake manifold.
Disconnect the alternator connector (A) and the p ...