PO420 Catalyst Below Threshold
PO420 Catalyst Below Threshold Code only
This code appeared and I did a few things like cleaning the manifold and
engine, then shut off the code to see how long til it re appears(did this a
few times). It seems to come on only at high elevation, whenever driving to
the Mountains.
Next, took it to emissions testing and it passed, even after a few months of
the Check Engine Light being on.
So if the emissions pass, does that just mean i need to replace O2 Sensors
since the emissions are perfectly fine?
