catalytic converter

I have a 2003 Jeep Liberty 3.8 Automatic and am not able to pass my state inspection as the computer shows that both O2 and catalytic converter "readings" are not clearing. They DO NOT show any error or code, they show nothing. The recommendation from the shop was to drive some more, with...

Ok, need some help with this please: 05 KJ, 280k miles. Brand-new spark plugs (the correct copper type) and refurbished all 6 coils at the same time. Had a P0172 code pop up. Cleared code and ran some injector cleaner through with a full tank of gas. Code returned along with p0456. Bought new...