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Question about O2 sensors

Discussion in '1st Gen. Tacomas (1995-2004)' started by samm895, Apr 21, 2010.

  1. Apr 21, 2010 at 5:14 PM
    #1
    samm895

    samm895 [OP] New Member

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    Stock, gutted cats
    2001 Prerunner 2.7 auto--I have check code for rear o2 sensor. I think its p0420, but can't remember. I was told that it was the catalytic converters, which I didn't want to replace. I took the sensors out and soaked them in rubbing alcohol overnight, reset the computer in truck, and check engine light stayed off for about 200 miles. After it came back on I decided to completely gut the cats assuming they were clogged. They are now gutted and flowing smoothly but the light still came on for rear o2 sensor. So my question is if I replace both the o2 sensors, will the sensors know if the cats are not in there, or will it fix my problem and have no check engine light? A little imput would be very much appreciated. Thanks
     
  2. Apr 21, 2010 at 5:42 PM
    #2
    kingston73

    kingston73 Well-Known Member

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    I don't think I would have gutted anything, but that's just me. Have you checked for exhaust leaks first? Have you noticed any other issues? Bad O2 sensors can cause poor mpg's.
     
  3. Apr 21, 2010 at 9:04 PM
    #3
    ETaco23

    ETaco23 Marshall offroad Fabrication

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    I have the same code and I or ready changed both o2 sensors and the light stayed off for about 2-3 months, but it just came back. My machanic (a buddy of ours) said that your sensor could have or ready burnt out. But I have a fealing that its my cat. which sucks! if it is!
     
  4. Apr 22, 2010 at 7:08 AM
    #4
    AlexanderD

    AlexanderD Well-Known Member

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    also have the same code. i was told it was just the sensor. have yet to change it though. i guess i should get on that.
    places to get one?
     
  5. Apr 22, 2010 at 7:11 AM
    #5
    98tacoma27

    98tacoma27 is gooder 'en chicken Moderator

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    The rear O2 is what tells the ECU how the CAT is functioning. With a gutted CAT you will have a CEL. There two options now since you have gutted the CAT:

    1) Replace the CATS
    2) Purchase an O2 simulator form URDUSA.com. It will trick the ECU into thinking the CAT is there and functioning.

    If you live in a State that smogs vehicles (emission tests), you will need to get a CAT.
     
  6. Apr 22, 2010 at 7:50 AM
    #6
    ShadowFalken

    ShadowFalken Well-Known Member

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    A P0420 is not an oxygen sensor code. It is a code to say that catalyst efficiency is testing low. It uses the sensors to test the cat (both upstream and downstream).

    The oxygen sensors are tested by various other tests and can set multiple codes depending on the type of problem. Most of them tend to be in the low to mid 100 range as opposed to the 400 range in the code list.

    If the cat was not bad, it is now. Gutting a cat on a highway driven vehicle is not legal. A sensor simulator is not legal for highway use.

    Best suggestion is to get the vehicle to a qualified tech for repair. You will have to start with a cat at this point.

    Everyone. Please understand. A code is not a final answer in the VAST majority of cases. It is a marker of a place to start. A code for an oxygen sensor can be caused by a loose connection or even an exhaust leak as examples. Cat codes can be caused by exhaust leaks, fuel control issues that are undetected, marginal (barely passing tests) O2 sensors, load calculation errors, or the need for a programming update because the original software was too restricted in testing.

    Guessing at this stuff can be more expensive than you imagine.
     
  7. Apr 22, 2010 at 6:11 PM
    #7
    ETaco23

    ETaco23 Marshall offroad Fabrication

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    ^^ Very true! That is why after replacing my o2 sensors, and having the light/code come back after 3 months or so. I am finally taking to my buddy who is a machanic, to run a diagnostic on it, to see what is really wrong. I really hope my cats aren't bad!:(
     
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