Ford Repair Questions? Ask a Mechanic for Answers ASAP
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as usual, auto zone is wrong. you do not need the valve cover.
more than that, it is not th pcv. that is common to both sides of the motor. the 174 is bank 2 lean only. I would suspect a vacuum leak somewhere on or in the intake manifold. very common for intake manifold gasket to be bad causing this code. there other possibilities but without setting the 171 along with the 174, it is just limited to the driver side of the engine.
on the passenegr side valve cover
and once again, it is not your failure