Registered: 12/30/10
Posts: 525
Loc: on the water.
It could be the o2 sensor but 99% of the time a new cat will fix this dtc. I've been told that you can put a spark plug antifouler from autozone on the rear o2 sensors and even without cats this dtc won't set but I don't know if thats true or not. It wouldn't cost much to test the theory out and if it did then removing the cat would be possible if you don't have an emissions test to pass. Don't put an aftermarket cat on because they will create this code as well since most don't clean the exhaust as well as what the computer expects.
It could be the o2 sensor but 99% of the time a new cat will fix this dtc. I've been told that you can put a spark plug antifouler from autozone on the rear o2 sensors and even without cats this dtc won't set but I don't know if thats true or not. It wouldn't cost much to test the theory out and if it did then removing the cat would be possible if you don't have an emissions test to pass. Don't put an aftermarket cat on because they will create this code as well since most don't clean the exhaust as well as what the computer expects.
It works best with 2 non-foulers & some steel wool between them.
Those O2 sensors have a bad habbit when they go bad of saying it's the cat when it's the sensor not putting out the right voltage and lieing to the computer.
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#6838431 - 11/12/1105:38 PMRe: P0420
[Re: David Lee]
lite-liner
Capt. CUDA
Registered: 07/01/04
Posts: 4546
Loc: little elm tx
might not be the cats. could be slow rear 02s. mileage? a good scanner will tell you, if you know what to look for. cat efficiency code is often symptom, rather than source.
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Registered: 12/30/10
Posts: 525
Loc: on the water.
If you want to eliminate the o2 for sure since the code is for bank 1. If you clear the code and switch the rear o2 sensors from the left to the right and drove until the light came back on. You'd know based on whether the dtc is a p0420 or if it changes to a p0421 whether its the cat or the o2 sensor. Thats the most cost effective and 100% sure way to know.
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