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Discussion Starter #1
This might seem like an easy or dumb question to other people but it's really bothering me. I have an 08 3.7L and I was wondering what do you do with the first O2 Sensor after installing the JTR Header.
 

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so you have to drill into the exhaust system? i was under the impression the header was pre-drilled for the sensor, you just had to extend the wiring for it...
 

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Discussion Starter #4
I'm confused. I Thought the 2nd O2 sensor went in the header it's self, in the provided spot, so where exactly does the other one go? Any one have a picture of it.
 

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ok, i read the JTR website about the header and supposedly all you have to do is extend the front o2 sensor wires approx. 2 1/2 feet and it screws into the header directly in front of the flange. Now with this being said...it says you will need a reducer to go from the header to the stock cat. Does anyone know if there is a high flow cat you can use to get even more performance from this upgrade?
and if you buy an upgraded pcm can it be tuned for the header install and a high flow cat? (if one is made)
 

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There's someone on here who's marketing a 3" cat-back system, including a high flow cat. Can't remember who. You'll have to use the search. PCM for Less could probably fix you up on the PCM if you give them your mods.
 

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Discussion Starter #7
Right. The instructions say extend the wires and install in the provided spot, but on the old manifold there are 2 Oxygen sensors. One before the converter and one after. It doesn't state which one to put in the spot provided and what to do with the other one. I e-mailed JTR but they haven't responded. I was hoping some one here has done the install and knows the answer. I was thinking that when it says, "If the truck is started without connecting the Oxygen sensor, the "Check Engine Light" will come on." That they ment without one of the O2 sensor hooked up the check engine light will come on. Hopefully someone could help because this was suppose to be a weekend project and I need the truck for work on Monday.
 

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ColoradoKid121205 said:
I think that's why it was not marketed for the 2007-2008 3.7L but on ly the 2004-2006 3.5L :D
Exactly.

You need to find out if the header flange openings are even big enough for the 3.7L's larger exhaust ports. If they are then you can make it work by installing the 1st O2 into the header and extending the 2nd O2 sensor's wires and installing it behind the second cat. If the ports are too big for the header then you'd be wasting your time as it'd just leave a big step for the exhaust gasses to pass over.
 

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Discussion Starter #10
The header does fit 3.7L I talked to JTR before buying it. Right now it is installed in my truck. I talked to a local exhaust guy and he said to make it smog leagal you need to remove the 2nd cat and put in an aftermart single cat designed for a single cat system. Then yes, drill a hole and weld a nut on right after the cat for the second O2 sensor. He also wouldn't guarantee that it would pass. I guess I'll know on Monday I'll let everyone know how it works out.
 

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Did you compare the size of the openings on the header flange to the exhaust ports, or are you just saying it fits because it bolted up?
 

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brakenit said:
Did you compare the size of the openings on the header flange to the exhaust ports, or are you just saying it fits because it bolted up?
check this before you attempt to start the truck!!
 

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Discussion Starter #13
It matches up, I already driven the truck -1 O2 sensor. I checked before putting the headers in. I didn't get out calipers and measure each port exactly but I made sure they would fit properly before installing them. Monday I'm going to the exhaust shop so they can put in a hole and weld a nut for the second O2 sensor. Right now it drives fine. I had to clear the code out because the check engine light bothers me but, evrything else is working just fine.
 

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after you cleared the light has it come back on? and in reference to the cat back exhaust system i really dont want to buy a cat back system i have a 2 chamber flowmaster with turndowns and i love the way it sounds, i get compliments on it all the time....i would just like to find the high flow cat if possible...
 

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Discussion Starter #15
The light itself doesn't come back on, But the code does come back after erasing it, if you scan the computer.
 

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OK i think i see whats going on. You see in 2004-2006 the first oxygen sensor goes before the cat in the manifold and the second oxygen sensor goes after the second cat, passed the first one in the manifold. This is why many folks have been able to gut their manifold cat and still not set a code, because the second cat is still there and the second oxygen sensor still sees cleaner exhaust therefore not setting a code.

However in 2007 they moved the position of the second oxygen sensor into the manifold after the first cat before the second cat to actually monitor the first cat's efficiency closer. Well the JTR header is made for the 04-06 style so of course there is no oxygen sensor bung for the second sensor since there isn't one on the 04-06s.

Here's the thing though, you can have an exhaust shop drill and weld in a second o2 sensor bung into the JTR header but its pointless as there is not cat in the header so its still going to set a check engine light with a P0420 threeway cat efficiency low. The best thing you could do is have the exhaust shop drill and weld in a o2 sensor bung in the exhaust after the second cat and this may not set the code but then again it may since maybe the second cat doesn't clean up the exhaust as well as the first one?? Or you can have HPTuners disable the second o2 sensor completely or get an o2 simulator.
 

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Something else i though of, you could see if you could install a second cat from a 04-06 that should bolt right on. Or just go with a hiflow one from magnaflow or something.
 

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ok so on the 04-06 theres only 1 o2 sensor up front right? and even so with the header its gonna set a p0420 right? will the pcm upgrade correct the o2 code? if not who makes an o2 simulator?
 

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1. 04-06s theres only 1 o2 sensor in the header before the cat then the second one is after the second cat. On 07s+ theres 2 o2 sensors in the stock header 1 before the first cat and then the second before the second cat instead being after the second cat therefore the JTR headers doesn't have that second o2 sensor bung.

2. It wouldn't matter if it did have the second o2 sensor bung in the header because theres no cat in the JTR header so it would set a P0420 thinking the cat isn't working. Now if you lengthen the wiring to the second o2 sensor and relocate it AFTER the second cat then it should be fine, unless the second cat isn't good enough to clean the exhaust enough to pass smog. All we know is the second cat seems to be good enough to keep the CEL off and no P0420 code.

But no one here with a 04-06 and gutted manifold has had theres smogged yet so no one knows for sure if having the second cat even still passes the sniffer smog.

3. I think using the HPTuners program you can disable the second o2 sensor so the PCM doesn't monitor it and therefore no CEL or code.

4. Don't know who makes an o2 sim but i know theres some out there. I think someone here talked about using a sparkplug defouler maybe search that.
 

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OK guys I made a mistake and i can't really confirm this physically since I don't have access to a 2007 and 2009 Colorado/Canyon/Iseries but from looking at the service manual, I think its only 2008 when they changed the location of the second o2 sensor. If anyone can confirm this that'd be great. So for now i went back and edited all my posts in here so as to not confuse anyone.
 
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