Trick computer

[Emerson]

Picked up Hotshot headers had them installed but the problem is, the check engine light comes on, and the car is due to go to inspection. No seems to know how to solve the problem. I had the O2 sensor moved that didn't do it, right now I may have to remove the headers and put back the stock manifold to get through inspection. Does anyone know how to solve this problem? Iv'e heard there's a way to trick the ECU into thinking that the motor is doing something it isn't. Could use some help.
Emerson
2003 Elantra 2.0 4dr sedan

[wazntme]

your first step would be to go get ur engine codes read to see what code or problem the computer is actually tripped over

[Jonny666]

Its likely your throwing a cel because yo removed the primary cat. you need to relocate your O2 sensors and you will be fine. try searcing Header cel, they'res 1000000000 threads on this already.

[BobMs_wht2k2]

You're not going to pass a visual inspection period. Headers are to be used as an offroad use only and that's why they trip your CEL. It's a FEDERAL law to not remove any of your emissions equipment, not just a state mandate.

So unless you have your old manifold to reinstall, you're S.O.L.

[2loud2k2xd]

pm evan about this. i think he got ride of his cel.

[evan938]

no, i didnt get rid of mine. it didnt show up for 4000 miles or so w/ my key header. i didnt worry about it though...didnt affect drivability and i wasnt gonna spend $ to get rid of the light

[ArunSenior04]

I bought one of those mechanical o2 sims. My cel is weird. It comes on, and goes away on its own. The only time it comes on, is when I floor it. But after a day or two, Ill cut the car on, ad itll be gone. As long as I dont floor it, it never comes on.

[XDGT03]

An ECU reset should clear the code for a little while.

[ricerrx7]

But the car has to have gone through so many drive cycles in order to pass the inspection.

[jrod13]

I have an OBX header, and have at least 60k with the header on it, and only got a CEL once for 90 miles or so then it went away. All I did was have a o2 bung welded into for the primary sensor. For some reason I think it is a fluke that mine hasn't come on more though. When I did have the light on I brought it to Hyundai they scanned it and diagnosed it as "Catalytic Converter deficiency code" then made a special comment that said "Needs cats re-installed". I lollerskated the whole way home.

[thewilson]

I just woke up think this makes sense:
Cat Back Exhaust maybe as an alternative or stick your cat back on after the headers get some wire and put the 02 sensor after the catalytic converter. my friend's brother has a high flow cat and catback exhaust. might not be as good of a benefit as headers i don't know I know that a high flow reduces emissions but not enough for the state so they just swap out the highflow cat with the stock one when inspection time comes which is not too much of an inconvenience this is up near austin tx btw probably not exactly the same requirements down this way vs up there

[menallychllngd]

the sensors need to be on either side of the cat that you have left they need to read that there is a difference in o2 emissions between the two points. if this does not work i suggest either taking the light out or having the ecu programed to turn the light off. i had a friend with a sentra and thats what he had to do when he went catless.

[focusXD]

umm look up an o2 sensor cheater. a LOT of focus' use them. rather useful, and if the inspection place doesnt stick an exhaust meeter on your tail end and just goes off an ECU reading, you'll pass. also another trick for passing inspections when you have no cat, use 93 octain gas and turn on your AC when you get there. hopefully they wont turn it off. I dont know how it works with the AC, but i have been told it helps with emissions somehow

[Ugzz]

ok, im a super dummy and 100% clueless when it comes to cat back and headers etc as ive never even seen talk of this stuff till this forum.. so let me get this strait, if i put headers on my car i wont pass emmisions anymore and my light will come on? Also if you do new headers can you leave all the cats in place or do they have to come off?

sorry for the dummy questions, but i literally have no clue.. im just interested in starting to learn little by little from reading similar posts..

tx for the info

[thewilson]

AsFariAsIKnow*
Headers = no cat anymore if you put one on it would be like under the car somewhere and prolly wouldn't pass a visual dunno i've never had a visual inspection before and it would probably get broke down that way
Cat back = exhaust from the catalytic converter back so all the work is under the car
depending on your state you might be able to get away with a high flow cat meaning its not as restrictive but also doesnt reduce emmissions as much like i mentioned my friends brother just switches them out during inspection time.

again i might just be blowin smoke but thats how I understand it.

this guy down here
mtlelantra
|
\/
has got it down

[mtlelantra]

Depends on the state. Depending on the state, if it's not stock, you won't pass. Other states if they see a CEL, you won't pass. Some states don't care, much like Canada. You might not necessarily get a CEL, but there's a high probability.
The stock exhaust systems has two cats and two O2 sensors. The 1st O2 sensor you can see on the exhaust manifold, and it's right before the primary cat, which I believe is one piece with the exhaust manifold. There's a down pipe, a flex pipe, the 2nd O2 sensor, and then a secondary cat for those "just in case" emissions. So what the computer is doing is comparing the signal between the 2 O2 sensors to make sure your primary cat is doing its job. ADDED: (the 1st O2 sensor also checks for completeness of burn, and adjusts A/F ratio accordingly).
When you put on an aftermarket header, you're getting rid of the primary cat. Some headers already have a bung for the 1st O2 sensor, but if you install it without relocating the 2nd cat, both sensors will essentially read the same value and throw a CEL.
So what ya gotta do is 1) for the best chances of not throwing a CEL, you need the 1st O2 sensor to be at the final collector (i.e. where everything runs into the final single exhaust pipe at the end of the header. If you have a 4-2-1 and it has an O2 sensor at one of the "2" collectors, you're only reading 1/2 the exhaust, so there will that much less of a difference between the 1st and 2nd O2 sensor values.
2) you can keep the secondary cat and use it in place of the primary cat, or install a high flow cat or whatever.
3) you need to relocate the 2nd O2 sensor so now it's behind the "only remaining" cat. Some people have measured the stock distance between the primary cat and the 2nd O2 sensor, and translated it when they install the headers. Probably a good idea.
What these "mechanical" O2 simulators do is pull the 2nd O2 sensor out of the direct stream of the exhaust, so now the 2nd O2 sensor is only reading a portion of the exhaust gases, again, magnifying the difference between the sensor values.

[Ugzz]

Ah ok, thanks for the in depth explanation, that helps alot!

[BobMs_wht2k2]

TECHNICALLY: The removal of any emissions equipment, especially catalytic convertors, is prohibited by FEDERAL law. Yes, those of us lucky enough to not have state required emissions testing can skirt it, but it is still illegal. Anyone facing a visual inspection might as well right off headers as a viable modification as they are NOT emissions legal in any state.

[Jonny666]

I started a thread many a moon ago where people could post pics of their header install's and explain how they dealt with the CEL issue. ONLY 3 PEOPLE responded and posted pic's. it was a total failure.
2 of those people ( including myself) relocated the O2 sensors to get rid of the CEL and the third still had a cell.