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i lost my rear o2 sensor

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Boostin95RST

15+ Year Contributor
147
0
Mar 17, 2008
cleveland, Ohio
i bought this 95 eclipse and it already had a turbo back exaust, no rear 02 and no cat. i bought a highflow cat and a universal 02 to put on it, well when i got the car in the air , there isnt anywhere to wire in this sensor at all, it is missing and i was just wondering if someone could explain where the clip/wireing should be at. it is a 95 rs model. thanks
 
i bought this 95 eclipse and it already had a turbo back exaust, no rear 02 and no cat. i bought a highflow cat and a universal 02 to put on it, well when i got the car in the air , there isnt anywhere to wire in this sensor at all, it is missing and i was just wondering if someone could explain where the clip/wireing should be at. it is a 95 rs model. thanks

The rear O2 sensor should be directly after the catalytic converter. Just crawl under the car and look up around the floor pan in that area to see if maybe the previous owner zip tied the connector out of the way or something.
 
Unless you have to pass emissions tests, you don't even need a rear o2 sensor, just the front. The rear is only there to check if the cat is working, and with your high-flow cat (unless you bought a name brand one) might trip the o2 anyhow since it isn't really a cat. If you don't need to pass emissions, then I would say forget it, but if you do look into oxygensensors.com
 
The wiring for the O2 comes out right under the driver seat. If you want to get to it, you have to take the driver seat out and the centersole. It is right under the carpet after you get those parts out. It goes down through the floor through a rubber grommet.

Good luck!
 
A faulty or missing rear O2 sensor can still have an affect on performance. It might not throw the car into limp mode, but the ECU still adjusts for the worst case scenario.
 
no its not a bosch and i didnt buy it at a parts store. i got it off ebay ### they were only like 20 bucks. i do have an emisions to pass but i dont have to worry about it for a while seeing is how the whole thing is in peices, the interior is gutted down to the steel so i will check for the harness.. but with that high flow cat, should i even worry about putting the o2 on there, or should i just try that bypass method...
 
I would bypass it. Simply because the high flow cats sometimes (but not all the time) really don't function as a cat. Might as well do that while your interior is gutted anyhow, then you don't have to worry about it too much since it is easily accessible.
 
So what brand is this o2 sensor you got off egay?

Paul, just tell em it was the wrong kind and throw a fit LOL.
 
Paul, just tell em it was the wrong kind and throw a fit LOL.

It'll have to be some fit... it usually says right on the box "confirm this is the right oxygen sensor before installing, we will not accept installed sensors for refunds under any circumstances," etc..
 
BECK ARNLEY O2 SENSOR 90-04 MITSUBISHI ECLIPSE
i bought 2 of them, one for front and back. when i bought the car it didnt have anything...
 
I have a magnaflow high flow cat, threw a cel because of my rear O2 sensor, and as soon as I replaced that, light is gone, passed emissions, and all is well. :thumb: I recommend if you are doing it, get the correct one, not universal, because then it's plug and play. The harness is under the driver seat.
 
How bout o2 simulators? Do they even work? I have the same problem, except that I'm
running a test pipe. So i already have the CEL light or code for faulty cat converter.

Another question maybe off topic. Got my DC Headers today only problem is that there isn't
a place for my upper o2 sensor. Any suggestion as to how i can fix this. Or maybe i don't
need it ether?
 
o2 simulators do work.

Your header should have a o2 bung after the collector, if it doesn't have a muffler shop weld one in. The upstream o2 sensor is required for normal operation of the ECU.
 
:thumb: Thats exactly what i did bro. I took the car to the muffler shop, they welded the o2 sensor right before
the flex pipe. I had them do a 2.5 inch exhaust piping all the way to the muffler. Sounds real mellow now thou. The only
thing is that i tried a home made o2 sensor simulator, and now the ECU threw a code: Upper o2 sensor at center more than a minute and a half. If i run the car with out the lower o2 sensor the upper one reads a rich condition. Supposedly both are linked somehow.

I need help figuring this out. I'm running Cat less now so a lower o2 sensor would only throw a
faulty Cat converter code. Anybody out there running test pipes had this problem and
somehow solve this?

O and sorry Boostin95RST for hijacking your thread. ;)
 
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