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Discussion Starter · #1 ·
So I was looking through the service manual, and I noticed that the "front bank, sensor 2" O2 sensor is part of the precat assembly (#12).


The problem comes in with that fact that I also noticed that the xtech manifold that I have, doesn't have a place for the second O2 sensor. The xtech manifold completly replaces both the precats, so in doing so it will eliminate the second O2.

Now I was wondering what are your thoughts on this? I was always under the impression that the two O2 sensors (the ones before the precats), were actually used by the ECU.

Thanks again guys! (sorry for the recent onslaught of question ~ turns out the more I learn, the more questions I have lol)
 

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you still have a main cat right? you just have to put the after cat o2 sensors after the cat (usually you have to extend the wires) they don't have to be on the same "location" as the stock manifolds. These sensors are used by the ECU to make sure you have cats in place and that they are working correctly.
 

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Discussion Starter · #3 ·
pacoslant said:
you still have a main cat right? you just have to put the after cat o2 sensors after the cat (usually you have to extend the wires) they don't have to be on the same "location" as the stock manifolds. These sensors are used by the ECU to make sure you have cats in place and that they are working correctly.
Oh I understand that about the secondary O2 sensors. Though its the primary O2s that I'm worried about, not the secondary ones. I have no place in my turbo manifold to stick the 2nd primary O2 sensor in.
 

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Jetblackness said:
Oh I understand that about the secondary O2 sensors. Though its the primary O2s that I'm worried about, not the secondary ones. I have no place in my turbo manifold to stick the 2nd primary O2 sensor in.

oooh I see. How does the manifold look? can you post a pic it? you should have a primary o2 per bank if there's no bung for it, get one welded on there. Maybe that manifold was for a fed spec?
 

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Discussion Starter · #5 ·
pacoslant said:
oooh I see. How does the manifold look? can you post a pic it? you should have a primary o2 per bank if there's no bung for it, get one welded on there. Maybe that manifold was for a fed spec?
Here it is:


It's supposed to Cali spec, and no theirs no extra bung on that piece. See the ting is, on the other side, the stock exhaust manifold has a bung in it already. On this side, the bung is located on the precat (as opposed to the stock mani). So by installing this, I will be getting rid of both precats. Now thats not a problem for the front side since the sensor isn't on the precat.
 

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ok ok, I don't quite get what you are saying but: You have to have one primary o2 sensor per bank BEFORE the cat and the other two AFTER the cat. The primaries can go either on the stock manifold or the downpipe as long as they go before a cat. If you need to weld an extra bung to acomplish this, do it! It should be:
manifold --> primary o2 sensor --> cat --> o2 sensor --> catback
or if you are not using a cat you need to use some kind of sim on the "after cat" sensors. Does this make sense? lol from looking at the pic it looks like you have to add a bung on the rear bank.
 

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Tearstone said:
Jet black, take the o2 sensors you would normally have after your pre cats and extend them behind your main cat.
that sound a lot easier :twothumb: I made it sound so complicated :bash:
 
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