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-   -   cat removal options ,02 sensor 2 code removal (https://www.jk-forum.com/forums/modified-jk-tech-2/cat-removal-options-02-sensor-2-code-removal-80776/)

mEthOdsOMahAn 04-07-2009 01:32 PM

cat removal options ,02 sensor 2 code removal
i rolled my jk . when i was replacing the frame i noticed 2 of my cats were damaged due to contact with the bent frame . a new y pipe with all 4 cats is definatly out of my price range . is there any way to remove the sensor 2 02 codes from the pcm ? OR does anyone have any other options ? there are no emission testing currently in my area, so that is noy a problem for me .

RedneckJeep 04-07-2009 01:36 PM

Yeah. Borla makes some long tube headers that comes with a new Y pipe that has no cats.

mEthOdsOMahAn 04-07-2009 01:51 PM

Originally Posted by RedneckJeep (Post 1048490)
Yeah. Borla makes some long tube headers that comes with a new Y pipe that has no cats.

removing the cats is not the problem . getting the check engine light off is my main concern

JPop 04-07-2009 02:01 PM

Are the O2 sensors currently attached?

mEthOdsOMahAn 04-07-2009 02:08 PM

Originally Posted by JPop (Post 1048533)
Are the O2 sensors currently attached?

currently i removed the bank 1 cat 1 &2 . i put cat 2 in cat 1s place and a straight pipe where 2 was . this has worked fine for about 3k miles . now i believe that bank 2 cat 1 is also damaged . exhaust was rattling and now it has a raspy exhaust note . so i am wanting just to remove all 4 and be done with it . i also notice there are no 02 sensors after the rear 2 cats like most other vehicles have . and to answer your question is YES all 4 02 sensors are in the stock locations . i would like to remove the rear 2 as its my belief that they only monitor cat condition BUT i do not want the CEL on .

d0wnShifT 04-07-2009 02:57 PM

There were ways to defeat the O2 sensor CEL in my Volkswagen GTI that other people were doing that I fortunately didn't have to do because of my aftermarket programming. What they did was get spark arrestors and thread them into where the rear o2 sensor goes on the header... then put the sensor on the end of it. Logic for this was that it still would heat the sensor, but put it far enough back in the exhaust stream to keep it from getting a CEL. Results were mixed with this solution. Here's a pic of the arrestors and 2 links for more information...


mEthOdsOMahAn 04-07-2009 03:04 PM

ya , i was going to try the little tube that raises the rear sensor out of the exhaust path . i just dont see this working very well but everyone says it does . i know on gM vehicles trouble codes can be removed completely . this is what i would like to do .

RedneckJeep 04-07-2009 03:41 PM

Originally Posted by mEthOdsOMahAn (Post 1048516)
removing the cats is not the problem . getting the check engine light off is my main concern

Then buy some O2 sensor simulators. Pretty simple really.

mEthOdsOMahAn 04-07-2009 03:46 PM

Originally Posted by redneckjeep (Post 1048726)
then buy some o2 sensor simulators. Pretty simple really.

in theory !

whpony96 04-07-2009 03:56 PM

1 Attachment(s)
I have them on my mustang and they are called MIL Eliminators... (Malfunction Indicator Light)

It's a simple 2 component circuit really..

MIL Eliminator
If you are one of the people with '94 and up MN12, and thinking of making a straight exhaust with no catalic converters, you may run into problems since your model car has OBDII sensors behind each cat. If you remove the sensor computer may be getting wrong readings.
But don't worry.
There is a special device called a MIL Eliminator that you can get at www.dallasmustang.com ($60 + S&H), that will reroute the signal correctly to the computer without having the OBDII sensors in.

The device just plugs into the back of the rear O2 sensors and they send a signal that tells the computer that everything is ok, just as the O2 sensors would if the cats were there.

* - Also, if you are going to remove all the cats be careful that you have enough backpressure or you will lose low-end torque. I have heard this is a common occurence when you gut or remove the cats. You can put one 3" in/out Flowmaster or a Resonator where the third cat used to be to fix this.

There is also a way to build a circuit that will work just like the MIL Eliminator.

Here is a link to the diagram that you can build it on your own if you are good with electronics.
Make a circuit that reads the voltage of the first o2 then injects a corresponding voltage into the harness connection for the second o2. A couple of diodes and resistors is all that is needed.

Q: Knowing that the O2 sensor has a limited life and loses its sensitivity over time, could you swap the positions of the before CAT and after CAT sensors to put a less "used" one in the before position? I am assuming the after CAT one gets less corrosive elements.

A: The sensor's output is driven by the O2 content. Steady state below about .40volts means there is excess oxygen from stoichiometric levels and steady state above about .8 volts means less oxygen than the stoich level.
I am just guessing now, but if the catalytic converters are scrubbing excess oxygen ions from the various oxides produced in combustion, then the voltage should always be higher in the post-CAT sensor than in the pre-CAT sensor indicating to the PCM that the CATS are working properly.
I would venture to say from that guess that if you could drive 1.0 volts into the second O2 sensor harness you would fool the PCM.


CATALYTIC CONVERTER: OBD-II monitors the operation of the catalytic converters by a double set of heated exhaust gas oxygen sensors (HEGOS or O2). Comparing the oxygen content of the exhaust gas entering the converter with the oxygen content of the exhaust gas exiting the converter. OBD-II reports and stores catalytic conversion activity.

If you remove the catalytic converters, the oxygen content will be the same between the 02 sensors. Shortly after OBD-II will intercede and the CHECK ENGINE light (MIL) will illuminate. If you ignore the CHECK ENGINE light long enough, OBD-II will enter LOS (limited operation strategy) or "limp home mode".

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