Headers P0420 Code
Thread Starter
Pro
Joined: Jun 2006
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From: Marysville WA
Headers P0420 Code
After header, high flow cat, stinger install I get P0420 code. I have read all the threads that come up in a search of the forum so I understand this is fairly common after a header install but I had a couple of questions I didn't find in the search I was hoping someone knew.
1. Why would only bank 1 (driver's side high flow cat) be throwing a code? What I mean is why don't get P0430 as well? I have gotten and cleared P0420 twice, but never gotten P0430.
2. I don't plan on going with O2 sims, but may just go have the car tuned and have them tuned out. MY question is, if the CEL is disabled with a tune for the rear O2's, will an OBDII reader still show the codes being thrown? In other words, does it stop the codes from being thrown, or just the light from coming on? Thanks in advance.
Cheers
1. Why would only bank 1 (driver's side high flow cat) be throwing a code? What I mean is why don't get P0430 as well? I have gotten and cleared P0420 twice, but never gotten P0430.
2. I don't plan on going with O2 sims, but may just go have the car tuned and have them tuned out. MY question is, if the CEL is disabled with a tune for the rear O2's, will an OBDII reader still show the codes being thrown? In other words, does it stop the codes from being thrown, or just the light from coming on? Thanks in advance.
Cheers
Team Owner
Joined: Jan 2004
Posts: 38,772
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From: Boston MA
St. Jude Donor '06-'07-'08,'12-'13
You will get that code
I had the same issue
you need to find someone with EFI live and have it masked out
It because when the car is cold or ideling you are getting a LEAN condition on one of the 02 banks
I use to get that every other day it drove me nutz !
I had the same issue
you need to find someone with EFI live and have it masked out
It because when the car is cold or ideling you are getting a LEAN condition on one of the 02 banks
I use to get that every other day it drove me nutz !
Thread Starter
Pro
Joined: Jun 2006
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From: Marysville WA
The ironic thing is that it doesn't happen at all when cold or at idle. The code comes up if I accelerate sharply and then have to suddenly slow - like when you are accelerating and then the light in front of you turns red and you have to stop. Or you are accelerating to pass someone and some asshat decides to pull out in front of you and make you hit the brakes and slow.
Did you only get one code" I.e. just P0420 or just P0430? Also will the code remain even though the light is out if you have it tuned out? Thanks!
Did you only get one code" I.e. just P0420 or just P0430? Also will the code remain even though the light is out if you have it tuned out? Thanks!
Race Director
Joined: Jan 2001
Posts: 11,183
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From: Castle Rock CO
St. Jude Donor '15
The problem with this is that your tuner is only able to tell the computer to not set the dash-board light, but the code is still set within the PCM/ECM. The states with OBD-II emission scans will see that the post O2 test routine failed and, thus, you fail emissions for the vehicle.
Todd
Todd
Le Mans Master
Joined: Oct 2006
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From: Bradenton, FL & Chandler AZ
St. Jude Donor '09
Why not O2 sims? I had same issue after headers and got the sims from CF member CBRF4i1. Presto! Problem resolved. I have not had any more codes for over 6,000 miles. It was an inexpensive fix for an annoying problem.
Team Owner
Joined: Jan 2004
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From: Boston MA
St. Jude Donor '06-'07-'08,'12-'13
The problem with this is that your tuner is only able to tell the computer to not set the dash-board light, but the code is still set within the PCM/ECM. The states with OBD-II emission scans will see that the post O2 test routine failed and, thus, you fail emissions for the vehicle.
Todd
Todd
Not true
with hp tuners you can mask the code out completely
so it will neve report to the computter again
Race Director
Joined: Jan 2001
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From: Castle Rock CO
St. Jude Donor '15
Todd
Team Owner
Joined: Jan 2004
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From: Boston MA
St. Jude Donor '06-'07-'08,'12-'13
While I have heard this, I have not seen a definative answer on the test routine question. The OBD-II computer MUST run various check routines and that is what the emissions scanners look for. If the test routine doesn't pass, then the routine shows as failed AND a PO420/PO430 code "could be" set. The "could be" depends on how many attemps the ECM has made to pass the routine. Now, this info is a bit dated on my part, but I do attempt to stay up to date and I have NOT seen a post from any tuner saying they can successfully get this routine through emissions scan.
Todd
Todd
There are manny people here who have done this incluing myself
Its all about the tuner
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Thread Starter
Pro
Joined: Jun 2006
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From: Marysville WA
Thanks for all of the replies. I am going to try the simple step first - checking to make sure there are no exhaust leaks. If there end up being no leaks then I will go from there. I am not worried about an emissions test, just don't want a code popping every day...
Instructor
Joined: Jan 2007
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exhaust leak will not cause this code. p420 = driver side rear o2 sensor has too much activity = cat not working / lighting off the unburn gas.
Pro
Joined: Apr 2007
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From: Arvada CO
I don't mean to hijack this post but I have a question on this very issue that I started a post "do I need rear O2 sensors for my header?" In the next few weeks, I will install headers myself and I too don't want codes everyday in my daily driver. What is the best setup for the O2 sensors. thanks
Race Director
Joined: Jan 2001
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From: Castle Rock CO
St. Jude Donor '15
Todd
Race Director
Joined: Mar 2005
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From: Austin Texas
While I have heard this, I have not seen a definative answer on the test routine question. The OBD-II computer MUST run various check routines and that is what the emissions scanners look for. If the test routine doesn't pass, then the routine shows as failed AND a PO420/PO430 code "could be" set. The "could be" depends on how many attemps the ECM has made to pass the routine. Now, this info is a bit dated on my part, but I do attempt to stay up to date and I have NOT seen a post from any tuner saying they can successfully get this routine through emissions scan.
Todd
Todd
Team Owner
Joined: Jan 2004
Posts: 38,772
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From: Boston MA
St. Jude Donor '06-'07-'08,'12-'13
I'll certainly research, but maybe you can provide the absolute answer now. Did you vehicle have a PO420/PO430 issue after headers/high flow cats and/or no cats? If so, after a tuner "fixed" it, did you go through a state emissions inspection that uses an OBD-II compliance scanner?
Todd
Todd
I was getting the code every time i drive
After masking it out I got my inspection sticker with no problem
I have a hand held scanner
I use to have to clear the Code all the time
Now i do not get the CEL and i can scan it any time and there are NO CODES stored in my car !!!!!!!!!!!!!!!!
Team Owner
Joined: Jan 2004
Posts: 38,772
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From: Boston MA
St. Jude Donor '06-'07-'08,'12-'13
Here's a definative answer; Corvettes of Westchester tune will get rid of the code p0420 & p0430 and they are not stored in the computer. My car passed the Texas OBD2 emissions with no problems. No codes shown , stored or pending. Chuck was able to explain it to me, if you require a Tuners explanation maybe you should call him.
Any knowledgeble tuner can fix this issue
Instructor
Joined: Jan 2007
Posts: 182
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I don't mean to hijack this post but I have a question on this very issue that I started a post "do I need rear O2 sensors for my header?" In the next few weeks, I will install headers myself and I too don't want codes everyday in my daily driver. What is the best setup for the O2 sensors. thanks
i would installed the rear o2 sensors with your hi flow set up and see what happens. you could get luck and not get any codes, many has reported that they never got any codes, but at the same time there are many that do get the codes. so installed the rear o2s and see what happens. if codes does show up, o2 sims it or tune it out. your choice.
