+1 Y'up...0423 is after the cat

 

How does the pre cat sensor read catalyst efficiency if its sensing exhaust BEFORE the cat. Just my .02, but the post cat sensor makes more sense with the way the code is worded

 

Exactly, Someone gets the big picture

http://www.p0420.com/ <-- Reading material for the ****ter

Rear o2 is what is throwing the code, but not necessarly the reason for the code.

 

Jesus Christ, p0420 is not an o2 sensor code. Its for catalytic converter efficiency. Basically your cat is dead. Meaning its no long cleaning the emissions from your engine. Don't replace your 02 sensor your wasting your money. You should replace (or hollow out) your cat. BTW If you hollow it out your going to get a cel.

 

Po420 IS an o2 sensor code. The catalyst efficiency is read by the post cat o2 sensor. It is possible that the o2 is lying to the pcm because it is faulty. Therefore the root of the problem could be that the o2 is bad or the cat is sh!tting the bed.

Only reason I asserted my opinion on the meaning of the code is to shoot down the naysayers with some good ol' logic. My money is on the cat being clogged by a blown plenum, but we cant rule the o2 out of the equation.

Edit: If you gut your cat there is a quick and painless way to eliminate the CEL. Use the spark plug non-fouler trick which can be found in the faqs section here (works for me and many others on this site). It is quick, easy and will set you back a whopping 5$. NOTE: If you must pass smog emissions (i.e. they put a hose on your exhaust) you will not pass with a gutted cat

 

well if your replacing the cat just do your sensors too. might find better fuel efficiency with new sensors and new cat. BTW if you have problem with emissions move to a state without them. ha ha +1 for Minnesota.

 

Dont fix what aint broke. If your o2s are good, leave them there.

 

Right out of our own FAQ section, https://dodgeforum.com/forum/1582321-post6.html. 1/1 means bank1/ sensor1. We can argue all day about what catalytic converter efficiency means, but 1/1 is the precat sensor.

 

Everytime i check different sites about the code it sayd it is the o2 sensor not the cat it self, so I am taking it is the sensor just before the cat.

 

So what is it- the cat or the o2 sensor? I think it is the o2 sensor.