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Old 01-14-2005, 08:08 PM   #1
jalow72
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Default Bad Mil Eliminator or Bad O2 Sensor?

I keep getting a P0137 code every 120 to 150 miles. That is low voltage, 2nd O2 sensor. I installed a new turbo Sunday and in doing that had to remove the downpipe. So I wonder, did I damage the O2 or did I jack up the connectivity with the Mil eliminator when pulling on the cable? It just stumps me that it takes 120 to 150 miles to throw the code. Any ideas?
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Old 01-15-2005, 03:34 AM   #2
rewt
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i have actually been doing a lot of research recently on O2 sensor related problems, and i learned the following...

you either have a faulty rear O2 sensor, or it's not connected correctly. the MIL eliminator you have installed is only for the catalytic inefficiency CEL you get when switching to a catless exhaust. the CEL you have relates to a problem in the rear O2's heater circuit which has nothing to do with your MIL eliminator.

check the harness and wiring... hopefully, it's just a bad connection.
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Old 01-15-2005, 10:56 AM   #3
jalow72
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I believe that the mil eliminator in on the voltage return wire and uses a resistor to alter the signal to the ECU. In addition I believe that the ECU also monitors the voltage level on this return wire to determine the health of the sensor. I guess the question I should have asked was if the sensor goes bad, does it go bad right away or is it a slow death? I think that if it truly was the Mil eliminator, the return signal would be broken and I would throw the code right away. I am trying to determine if someone else has experienced this problem. I can then figure out whether I need to buy a new Mil eliminator, a new sensor or that the wiring job is whacked, before I have to jack up and crawl under my car.
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Old 01-16-2005, 01:49 AM   #4
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okay, one more time...

the rear O2 sensor has two circuits: 1 circuit used for the sensor, and 1 circuit used for the sensor's heater. the MIL eliminator you have installed is spliced into the circuit used for the sensor to fool the ECU into thinking your catalytic converter is working properly. without the MIL eliminator installer, you would throw a catalytic inefficiency CEL (P0420, i think).

the code you are thowing is due to a problem with the second circuit: the heater circuit. the ECU monitors this circuit, and when it detects a problem, it throws the code you are getting. this CEL has NOTHING to do with your MIL eliminator. either your wiring/connection is bad, or your probe is dying (i don't think it's completely dead since your sporadically throwing the CEL).

you need to check your wiring and connection. if you have a friend with a WRX, try swapping in his/her O2 sensor.
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Old 01-16-2005, 11:43 AM   #5
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Quote:
Originally Posted by rewt
okay, one more time...

the rear O2 sensor has two circuits: 1 circuit used for the sensor, and 1 circuit used for the sensor's heater. the MIL eliminator you have installed is spliced into the circuit used for the sensor to fool the ECU into thinking your catalytic converter is working properly. without the MIL eliminator installer, you would throw a catalytic inefficiency CEL (P0420, i think).

the code you are thowing is due to a problem with the second circuit: the heater circuit. the ECU monitors this circuit, and when it detects a problem, it throws the code you are getting. this CEL has NOTHING to do with your MIL eliminator. either your wiring/connection is bad, or your probe is dying (i don't think it's completely dead since your sporadically throwing the CEL).

you need to check your wiring and connection. if you have a friend with a WRX, try swapping in his/her O2 sensor.
I was not aware of the heater circuit. Thanks for you help.
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Old 03-05-2005, 04:51 PM   #6
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For the purpose of providing a resolution for those who search, I ressurect this old thread.

The MIL eliminator wire came loose from the crimp on one side.

Problem resolved!
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Old 03-05-2005, 09:36 PM   #7
David Medina
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i had the same problem!! just fixed it too! my electical fix broke apart and thats why it wasnt reading right. i even had the mechanical fix on it too.

so i just solterd (sp?) the wire with some scrap wire and put it back on and works perfectly now.
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Old 03-05-2005, 09:59 PM   #8
burton1181
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Iwould put money on the 02 sensor
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Old 03-05-2005, 10:06 PM   #9
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a little off topic but does having a mil elim. installed while running stock downpipe possibly cause a CEL. i've never understood if the cel fix alters the signal a little to account for no cat or if it just gives the okay signal. when i put my car back to stock i kept getting a rear o2 sensor cel....
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Old 03-06-2005, 07:49 AM   #10
jalow72
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Quote:
Originally Posted by burton1181
Iwould put money on the 02 sensor
I would have taken that bet until I pulled off the O2. Loose wire in crimp = low voltage CEL every 60-80 miles.
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