Hey guys I know that one of the error codes is due to my Cat being too large and my check engine light comes on after I clear it maybe once a week.

My Question is the P0455 Error code comes on at the same time but seems a little more daunting then the P0420.

Because they always come on together is it just from my CAT or could there be a bigger issue?

 

Ok the 420 is because it is not hot enough, it is lean why is it lean? well a major vacuum leak will do that and that is where the 455 comes to play. It could be the gas cap but most likely a very common evap canister problem found on 06 on w bodies.
HOW TO:Replacing Evaporative Emission Canister Vent Solenoid Valve (PO455 error) and you need a tune

 

Thanks for the link... I thought it was actually the Cat I had installed since that's when the issue started to appear. This makes sense as some times my inboard says check gas cap.

I'll have to get on this soon... What kind of issues does this cause when left un-attended?