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I'm getting a check engine light, and when i run the code reader, a P0431 comes up (warm-up catalyst below threshold bank 2)

I'm assuming this is referring to the catalytic coverters. From my understanding, if i am having a catalyst failure, my car should either be really loud or have a drastic performance decrease, but i'm not experiencing any of these

After more research, i heard sometimes the O2 sensors also throw off this code. So i want to try changing the O2 sensors first before trying the cats.

I'm kinda car-retarded, and new to this board, so i have no idea which O2 sensor so pick up. I'm guessing the upstreams? is there one or 2 sensors? should i just change them both? pretty much, i need help changing the O2 sensors related to the P0431 code. i called my local parts dealer, they sell them for $125 a piece, and i can only afford one for now. Help is greatly appreciated, and help in layman's term is even more so.
 

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I'm getting a check engine light, and when i run the code reader, a P0431 comes up (warm-up catalyst below threshold bank 2)

I'm assuming this is referring to the catalytic coverters. From my understanding, if i am having a catalyst failure, my car should either be really loud or have a drastic performance decrease, but i'm not experiencing any of these

After more research, i heard sometimes the O2 sensors also throw off this code. So i want to try changing the O2 sensors first before trying the cats.

I'm kinda car-retarded, and new to this board, so i have no idea which O2 sensor so pick up. I'm guessing the upstreams? is there one or 2 sensors? should i just change them both? pretty much, i need help changing the O2 sensors related to the P0431 code. i called my local parts dealer, they sell them for $125 a piece, and i can only afford one for now. Help is greatly appreciated, and help in layman's term is even more so.
the code is for the front pre-cat. i had the same prob but it was for the rear pre-cat(P0421). if you're gonna replaced the 02, it's the front downstream.
i just ordered a universal 02 sensor and will try that first. if that doesn't solve the prob then i guess the pre-cat will need to replace. oh, and by the way if it's the pre cat, you might want to replace asap otherwise the motor will be shot.
i guess the v6 has a lot of problems with the pre-cats.
 

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the code is for the front pre-cat. i had the same prob but it was for the rear pre-cat(P0421). if you're gonna replaced the 02, it's the front downstream.
i just ordered a universal 02 sensor and will try that first. if that doesn't solve the prob then i guess the pre-cat will need to replace. oh, and by the way if it's the pre cat, you might want to replace asap otherwise the motor will be shot.
i guess the v6 has a lot of problems with the pre-cats.
how many miles on your V6? i'm trying to see how far i can get with mine.
 

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front downstream? so its just one O2 sensor, right? i almost bought myself the front upstream one also. thanks buschwack. im gonna buy the exact fit ones then and hope that's the problem.

and i got 130k miles on it. if it is the precats, i wouldn't be surprised. its well past the 80k warrenty, so if i do get those replaced, its coming from my pocket. goodbye $700+labor
 

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front downstream? so its just one O2 sensor, right? i almost bought myself the front upstream one also. thanks buschwack. im gonna buy the exact fit ones then and hope that's the problem.

and i got 130k miles on it. if it is the precats, i wouldn't be surprised. its well past the 80k warrenty, so if i do get those replaced, its coming from my pocket. goodbye $700+labor
yeah, i hope it's just the 02 sensor but being that car has that many miles on it, chances are the pre-cats are clogged.
i just got mine o2 sensor today, cost me $20 but it looks like it's very hard get it install.
i was just going to buy a used pre-cat($100-150) but i thought i'd try the 02 first.
 

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Discussion Starter #8
yeah, i hope it's just the 02 sensor but being that car has that many miles on it, chances are the pre-cats are clogged.
i just got mine o2 sensor today, cost me $20 but it looks like it's very hard get it install.
i was just going to buy a used pre-cat($100-150) but i thought i'd try the 02 first.
are those $20 O2 sensors those universal ones? i have no idea how to install those. even then the cheapest one i found was $50. a direct fit one would cost me $100+

and did you get your pre-cats at a junkyard?i would much rather save $$$ than pay extra money
 

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are those $20 O2 sensors those universal ones? i have no idea how to install those. even then the cheapest one i found was $50. a direct fit one would cost me $100+

and did you get your pre-cats at a junkyard?i would much rather save $$$ than pay extra money
yes, it's universal from ebay. it's borg wagner so it's not too bad. bosch are only a couple bucks more. some while ago, i've seen the direct fit for $60 shipped but couldn't find it anymore. so i went with the universal.

i haven't purchased the pre-cat yet but the used one i was looking at is from a junkyard. the good ones have anywhere between 20k-55k and they're around $100-250.
you can search them at car-part.com and try to get the 05 model pre-cat because most of them have less mileage on them.
 

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actually, i'm getting more confused about which O2 sensor it might be

I remember walking into an autozone, and people telling me bank 2 is front up/downstream(?) i can't remember

i searched on ebay to find an O2 direct fit sensor for pre-converter front. so this is upstream right? is that the right one that refers to bank 2?

this O2 business is confusing me.... maybe if i saw a schematic of whatever the o2 sensors, i can try making more sense of this.
 

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Discussion Starter #12
so are all the direct fit oxygen sensors the same? or do they fit differently?
 

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actually, i'm getting more confused about which O2 sensor it might be

I remember walking into an autozone, and people telling me bank 2 is front up/downstream(?) i can't remember

i searched on ebay to find an O2 direct fit sensor for pre-converter front. so this is upstream right? is that the right one that refers to bank 2?

this O2 business is confusing me.... maybe if i saw a schematic of whatever the o2 sensors, i can try making more sense of this.
my code P0421 is for bank 1 which is for the rear precat( right hand side) or rear downstream 02
so, in your case it's the opposite...bank 2 or left side- front precat ...front downstream 02

downstream 02 is after the precat...upstream is of course on the precat or before...hope this help don't want to confuse you
 

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I think I have the same problem. I threw a p0431 code also. But I was told that it could be a o2 sensor, or a pre cat going bad. I am not sure. I see there was mention in other forums of a pre cat melting. Would a symptom of the precat beginning to melt cause the engine compartment to become very hot. It gets so hot that you can barely touch the good prop. But the temp gauge reads normal. The temp gauge reaches normal after two minutes of driving even if it sits overnight. I am not sure where to go from here. What would some of the symptoms be if it where the pre cat. And what would the o2 señor symptom be. Any help would be greatly appreciated
 

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I got this code for front and rear but I have CPE headers on my car so I was thinking that they were physically further from the engine and under the car they weren't heating up as quick but if others are getting them on stock exhaust cars then I'm at a loss.

I have to pass emissions myself asap to.
 

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I got this code for front and rear but I have CPE headers on my car so I was thinking that they were physically further from the engine and under the car they weren't heating up as quick but if others are getting them on stock exhaust cars then I'm at a loss.

I have to pass emissions myself asap to.
for the CEL
O2 Simulator, E-commerce
****CEL FIX FOR HEADER INSTALLATION****
CEL FIX FOR HEADERS
 
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