Po420 code

I believe this is for my O2 sensor can anyone confirm?

 

I would check for an exhaust leak somewhere or your cat or cats are bad. That would be where I would look first. Then if that all checks out then use an OBD II scanner and monitor your o2 sensor voltage

 

How would I go about checking the cats?

 

Best way would be to remove the second cat and look through it with a light and if everything looks still together inside, and you can see through it easily, then maybe put back together and run some cat clean through the engine. That code popped up on my truck and found out it was an exhaust leak when everyone else wanted me to replace my second cat

 

Gotcha. I’ll give that a shot. I appreciate the help

 

You are very welcome.

 

I had this code a few weeks ago. Truck was running poorly - not so much rough, just poor mpg and power felt slack. Replaced the rear O2 sensor and magic happened - truck runs much better now.

My approach: given that the front Air/Fuel Sensor was replaced (just downstream of the headers on the 3.4) by the PO I figured it wasn't likely to be that. So I settled on the rear "downstream" O2 sensor (between the cats on the 3.4). Replaced that with a Denso unit and so far so good! If you've never replaced any of the sensors in your exhaust system that is also a route to consider. Checking for an exhaust leak as mentioned is surely a smart move, too. Good luck!