P0420 CEL code

[gsx 1]

I was wondering if anyone had some advice on a cel code p0420. My check engine light has been on for some time now and when i checked thats what i got. I still have my stock cat on so im just curious if anyone has any help on whether this could b just a simple sensor problem or will i have to replace my cat as well?

 

[nickk90]

might just be a bad rear o2 sensor

 

[907gs-t]

If your lucky it's an O2 sensor I replaced both my O2 sensors first and that didn't work so I replaced my stock cat and cat-back system and it still came back on after a while then I replaced the stock O2 housing along with the downpipe and it came back on so I replaced the exhaust manifold and it hasn't come back on but I did find the exhaust leak it was the gasket that is between the turbo and manifold that I replaced recently when I replaced my turbo so now it's all good.

 

[95TalonOwner]

Either bad o2 sensor or bad converter.

 

[white92talontsi]

Watch the front and rear 02's on a scan tool. If they both are reading close to the same then its time for a cat.

What your looking for is when the front 02 changes the rear will tend to follow. On a healthy cat the front 02 should dither rapidly while the rear 02 will more less stay constant to an extent.


sent from my evo.

 

[95blackGsTurbo]

These threads should have answered your question.
http://www.dsmtuners.com/forums/newbie-forum/292660-p0420-what-do-i-do.html
http://www.dsmtuners.com/forums/newbie-forum/269679-just-threw-p0420-cel-code.html
http://www.dsmtuners.com/forums/art...-o2-sensor-mechanical-fix-cel-code-p0420.html