Need advice passing emmissions.
Thread Starter
Pro
Joined: Apr 2023
Posts: 670
Likes: 358
From: Windsor, CT
Need advice passing emmissions.
Hi folks. So I bought a '99 FRC C5 last month from out of state, I currently live in CT. Because it's from out of state, I need to pass emmissions. This will be the final time in this state my C5 needs to pass emmssions, as they will not test cars 25 years old or older. The car is stock, has all the smog stuff still on it, but it does have LG LT headers, X pipe and high flow cats. I'm getting P0420 and P0430 - Catalyst system below threshold. This is highly likely due to the Hi-flow cats.
What would your advice be?
I'm not opposed to getting a tuner to tune out the codes, but I'm not sure if that on its own will cause me to fail CT emmissions. As far as I know, the ECM has never been touched.
What would your advice be?
I'm not opposed to getting a tuner to tune out the codes, but I'm not sure if that on its own will cause me to fail CT emmissions. As far as I know, the ECM has never been touched.
Running Guns & Moonshine
Joined: Aug 2001
Posts: 12,669
Likes: 7,303
From: CT
Ask me about the AIR system tomorrow - separate topic.
If you have an emissions specific code thrown, I don't *believe it will pass until it clears and can be checked off.
They will also fail for general failed codes. Some of those can be disabled with a tuner so they do not post a CEL. They still exist, just no CEL. So running a supercharged car on a speed density tune I would have my MAF throwing a CEL because it did not exist and was not plugged in and therefore gave no signal to the ECU. The factory ECU when it has no MAF signal kicks into speed density and that is how you get that to work. So I ran it that way and had the specific code thrown set to not trip a CEL.
As offered above, I don't believe this code can be simply turned off and get you to pass because of its emissions status. I could also be wrong as this isn't my strong suit. I should also remind that any change in tune requires about a week of driving before all the required emissions checks are completed and you are allowed to test for emissions. You will automatically fail if you go in before the checks have completed their X number of starts / heat cycles / time under X speed, etc.
If you have an emissions specific code thrown, I don't *believe it will pass until it clears and can be checked off.
They will also fail for general failed codes. Some of those can be disabled with a tuner so they do not post a CEL. They still exist, just no CEL. So running a supercharged car on a speed density tune I would have my MAF throwing a CEL because it did not exist and was not plugged in and therefore gave no signal to the ECU. The factory ECU when it has no MAF signal kicks into speed density and that is how you get that to work. So I ran it that way and had the specific code thrown set to not trip a CEL.
As offered above, I don't believe this code can be simply turned off and get you to pass because of its emissions status. I could also be wrong as this isn't my strong suit. I should also remind that any change in tune requires about a week of driving before all the required emissions checks are completed and you are allowed to test for emissions. You will automatically fail if you go in before the checks have completed their X number of starts / heat cycles / time under X speed, etc.
Instructor
Joined: Aug 2022
Posts: 243
Likes: 93
From: Ashburn, VA
Hi folks. So I bought a '99 FRC C5 last month from out of state, I currently live in CT. Because it's from out of state, I need to pass emmissions. This will be the final time in this state my C5 needs to pass emmssions, as they will not test cars 25 years old or older. The car is stock, has all the smog stuff still on it, but it does have LG LT headers, X pipe and high flow cats. I'm getting P0420 and P0430 - Catalyst system below threshold. This is highly likely due to the Hi-flow cats.
What would your advice be?
I'm not opposed to getting a tuner to tune out the codes, but I'm not sure if that on its own will cause me to fail CT emissions. As far as I know, the ECM has never been touched.
What would your advice be?
I'm not opposed to getting a tuner to tune out the codes, but I'm not sure if that on its own will cause me to fail CT emissions. As far as I know, the ECM has never been touched.
Are the o2 sensor in their stock locations? I know my 2004 has four 2 pre-cat 2 post and I know with headers and x pipe install some kits don't utilize the rear two o2 sensors and they must be coded out [hence the for OFF ROAD USE ONLY warning on all those kits] lol. I presume if they did hearders...they also did the mid pipe with an x pipe. if so, you may have two o2 sensor tucked up somewhere.
Joe
Instructor
Joined: Aug 2022
Posts: 243
Likes: 93
From: Ashburn, VA
If you have access to a scanner, maybe you can check the live data on the o2 values.
Joe
Le Mans Master
Joined: Jan 2001
Posts: 5,015
Likes: 508
From: Hilton NY
Those codes are generated by the downstream O2 sensors and mean the converters don't flow 100%, this causes the check engine light to come on. Several fixes are seen on Youtube, one is to add Cataclean to the gas tank another is to use 18 mm sparkplug antifoulers to space the downstream O2 sensors out from the exhaust flow. The one I used is to tune out the downflow O2 sensors. After the codes are erased and the check engine light is off, the GM driving cycle needs to be run at least once to make the readiness monitors reset. Most code readers will show the status of the readiness monitors which need to be ready to pass inspections.
Tech Contributor
Joined: Dec 1999
Posts: 32,910
Likes: 2,402
From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
As of 2021, (When I moved from CT to TX), they just plug into the OBD2 Port and look for Emissions Not Ready Flags, CELs ND DTCS. NO SNIFFERS! )
i
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Burning Brakes
Joined: Dec 2022
Posts: 1,033
Likes: 896
From: Nappytown MD
Same here in MD, took my 02 in last March and they just plugged in the ODBII and ran the report. They have a sniffer hanging on the wall, but I haven't seen them use it. For 2005 and newer, they added a self service Kiosk station outside where you just drive up and plug in and do your own test. once the vette hits 25, don't have to do it anymore, based on the current rules anyway.
Running Guns & Moonshine
Joined: Aug 2001
Posts: 12,669
Likes: 7,303
From: CT
Would the computer be happy if the rear O2s were simply run not in the pipes but clipped up somewhere in fresh air? My Z06 came to me that way and it passed CT emissions without my knowing, and without cats at all apparently. I didn't know, just went through emissions. I don't know what was or was not altered in the ECU
Thread Starter
Pro
Joined: Apr 2023
Posts: 670
Likes: 358
From: Windsor, CT
Well I passed emmissions. Found an O2 spacer for a few bucks and it worked! I highly recommend if you're getting P0420 and/or P0430. In my case I do have hi-flow cats, but the downstream O2s are kinda far down stream, like at the tail end of the tunnel plate far, nearly a foot away from the Cats.
Thanks for all the advice guys! It's rare that the first and cheapest solution is the one that works!
Thanks for all the advice guys! It's rare that the first and cheapest solution is the one that works!
Running Guns & Moonshine
Joined: Aug 2001
Posts: 12,669
Likes: 7,303
From: CT
I found this educational. I never would have thought to use a spacer. I was surprised that the Z06 passed when I bought it because I went through without ever getting under the car and only after passing did I realize that the prior owners had NO cats and had mounted the rear sensors to the heat shields with clips up and out of the way and/or maybe disabled them in the tune.
Oddly, my build is going to be far more emissions compliant than how I received it.
Oddly, my build is going to be far more emissions compliant than how I received it.
Instructor
Joined: Aug 2022
Posts: 243
Likes: 93
From: Ashburn, VA
Well I passed emmissions. Found an O2 spacer for a few bucks and it worked! I highly recommend if you're getting P0420 and/or P0430. In my case I do have hi-flow cats, but the downstream O2s are kinda far down stream, like at the tail end of the tunnel plate far, nearly a foot away from the Cats.
Thanks for all the advice guys! It's rare that the first and cheapest solution is the one that works!
Thanks for all the advice guys! It's rare that the first and cheapest solution is the one that works!
Safety Car
Joined: Aug 2011
Posts: 4,449
Likes: 409
From: Portland OR
Good job. The spacers get the sensor out of the flow so they read different than the fronts. Makes the ECU happy!
I passed yesterday in Oregon. It always passes because I tell it to. It’s always nervous time because it obviously doesn’t sound stock, and it stinks.
So this time they get the mirror on a stick out….two different guys. Even saw them wipe down the sniffer. But didn’t use it. I was sweating for sure.
It has what look like cats on it, and of course it’s very hard to see under being lowered a bit.
They passed me.
Next time it’s 25 years old and eligible for special purpose plates. YES!
I passed yesterday in Oregon. It always passes because I tell it to. It’s always nervous time because it obviously doesn’t sound stock, and it stinks.
So this time they get the mirror on a stick out….two different guys. Even saw them wipe down the sniffer. But didn’t use it. I was sweating for sure.
It has what look like cats on it, and of course it’s very hard to see under being lowered a bit.
They passed me.
Next time it’s 25 years old and eligible for special purpose plates. YES!
Race Director
Joined: Apr 2007
Posts: 11,152
Likes: 890
From: South Western Ontario
FYI, turning off all the codes for the rear O2 sensors and catalyst systems that they monitor will automatically set the catalyst tests to passed, and of course keep any O2 codes from turning on the CEL or being reported. Same applies to the AIR system.
Once you turn-off the codes the associated monitors are ready right away. I did it to my car and would be able to test it after about 10 minutes of driving.
Once you turn-off the codes the associated monitors are ready right away. I did it to my car and would be able to test it after about 10 minutes of driving.