CEL P0420 Help

[mazprot00]

ok so my cel came on a few months ago finally got it read and its P0420. i have a corksport exhaust with a highflow cat and an injen cai. after reading some of the other posts about the cel p0420 most of you think its uasually the o2 sensor so thats what im assuming is wrong. Just wondering which o2 sensor it would be and what the part number would be on getting a new one. My o2 sensors have never been replaced either.

since i just got a new highflow cat and exhaust i would like to think its not that. Went to the mazda dealer in town a couple of months ago to get some other stuff done and i asked them if they would check it they said that the reason was i was missing cat and it would be $700 to get the missing cat. i told them no and have been running a cel ever since.

 

[MS3_KIDD]

high flow cats are typically not as effective as the cats that come from the factory. how soon after the exhaust mods did the light come on.? id say do non fouler cel trick everyone else does and youll be alright. if the o2 sensors were getting "lazy" it would throw a slow response code. its not the o2 sensor.

 

[cougar10agREDUX]

http://www.bigdaddiesgarage.com/straight-cel-fix.html

corksport threw in a simulator like that when i got their exhaust. i was pretty excited. saves more room than using two non-foulers

 

[mazprot00]

well actually i got the cai installed a few months before the exhaust. The cel came on a few days before i installed the exhaust, so thats another reason i was thinking it was the o2 sensor. it isnt a big deal to have the cel on but i would like to get it fixed at some point

 

[MS3_KIDD]

question, how many cats are on the car? i was under the impression you car had one in the manifold and then you had one welded in to your cs exhaust as well?

 

[mazprot00]

stock has 2 right? and both are welded to the the stock exhaust right? if thats the case i have one high flow cat and its on the cs exhaust and was welded on by cs.

 

[MS3_KIDD]

theres the problem. im willing to bet you do not have have a 02 sensor after the cat in your cs exhaust. because the only monitored cat on the car is the on attached to the manifold. you have a 02 sensor in the manifold and one somewhere after the first cat because the first one is the only one thats monitored and thats the cat that is operating inefficiently

 

[mazprot00]

you are right i do not have an o2 sensor after the cat in the cs exhaust, but neither did the stock exhaust. so my question is how would it know that there is a problem when there was never a o2 sensor after the cat in the old exhaust or new one to monitor air flow. when i removed the old exhaust my friend and i thought it was weird that there was no o2 sensor after the cat(s) to monitor air. im confused as how the old exhaust was monitored if i never touched or moved an o2 sensor

 

[MS3_KIDD]

because your monitored cat is on/right under your manifold. the one farther down the exhaust is not monitored.
you have one 02 sensor in the manifold, and the other some where after closely after the cat thats attached to the mani. thats the monitored cat and the one that is bad.

 

[MS3_KIDD]

so in theory you spent money to have a cat welded in to you corksport exhaust that is not even monitored.