Dreaded P0420 code!

[animator]

What's your gas mileage like? I feel like my cats are killing mine. I get 15 city 16 hwy. Seems like everyone i read about is getting 20-21

17-18 mixed city/highway. 20.5 or so on highway road trips.

 

[lude and rude]

another thing to check into is when you take it to an exhaust shop have them fog the system and see if you have any leaks. i kept having the code pop up on my runner and finally looked over the system after replacing o2 sensors and my muffler pipe section and found the new exhaust gasket i had put in didnt seal up like it should.

the code has so many different variables to it, it can be something as simple as this. the ecu is reading the differences per cat and post cat.

 

[jgue467]

Leaks will kick out a 420

another thing to check into is when you take it to an exhaust shop have them fog the system and see if you have any leaks...

Yup - that's what caused mine, minor exhaust leak. It is the first thing listed to check in the FSM. Luck.