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P0420 keeps coming back

Discussion in '1st Gen. Tacomas (1995-2004)' started by tacomainthesun, Dec 30, 2018.

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  1. Dec 30, 2018 at 9:22 AM
    #21
    zero4

    #21
    zero4 Metal Cutter

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    Yup the heater circuit is what fails for me on the front. I get P0135 when my front fails. Just replaced my front yesterday. It lasted 8 years, Denso. My stock one lasted 9 yrs. Of course Denso is what I replaced it with again.
     
    zero4, Dec 30, 2018
    #21
    cruiserguy and eon_blue[QUOTED] like this.
  2. Dec 30, 2018 at 9:26 AM
    #22
    JayRolla

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    JayRolla Well-Known Member

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    Trd stickers for 10whp 32s on MK6 17s
    You could bypass the rear sensor. Then remove the cats. Then ecu only needs the front sensor for AFR adjustments.
     
    JayRolla, Dec 30, 2018
    #22
  3. Dec 30, 2018 at 9:28 AM
    #23
    eon_blue

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    eon_blue Okayest Member

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    Yeah I had a
    $13 P1036 Goupchn 5PCS Stackable Banana to Banana Plug Test Leads Soft Electrical Test Cable Wire 3.3ft/1m for Multimeter 1000V 15A
    P1036 for the rear...looked like it was covered in soot when I took it out. But I had pretty bad lean issues that killed my cats about a year ago so I think that sensor was on borrowed time. Replaced it with a Denso as well and all is good again.

    I could tell something was up before the code came on because my AFR gauge in closed loop was holding at +/-14.0 rather than 14.7 like it should be. After I replaced the sensor it went back to normal.
     
    eon_blue, Dec 30, 2018
    #23
    zero4[QUOTED] likes this.
  4. Dec 30, 2018 at 9:29 AM
    #24
    zero4

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    zero4 Metal Cutter

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    Boosted life. :thumbsup:
     
    zero4, Dec 30, 2018
    #24
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  5. Dec 30, 2018 at 10:20 AM
    #25
    tacomainthesun

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    tacomainthesun [OP] Well-Known Member

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    Why would he replace the sensor and say that it wasn’t reading before the fix then?
     
    tacomainthesun, Dec 30, 2018
    #25
  6. Dec 30, 2018 at 10:26 AM
    #26
    tacomainthesun

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    tacomainthesun [OP] Well-Known Member

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    tacomainthesun, Dec 30, 2018
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  7. Dec 30, 2018 at 10:26 AM
    #27
    cruiserguy

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    cruiserguy Well-Known Member

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    Because 'mechanics' say and do dumb shiz all the time.
     
    cruiserguy, Dec 30, 2018
    #27
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  8. Dec 30, 2018 at 10:27 AM
    #28
    Bishop84

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    Bishop84 Well-Known Member

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    It was likely reading, p0420 doesnt trigger on bad o2's. But I'm dumb.

    o2 sensors are the most commonly misdiagnosed item by DIY mechanics.
     
    Bishop84, Dec 30, 2018
    #28
    tacomainthesun[OP] likes this.
  9. Dec 30, 2018 at 10:28 AM
    #29
    eon_blue

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    eon_blue Okayest Member

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    I would get ones designed specifically for your truck...that one has an o2 sensor bung in a spot different from where our's goes
     
    eon_blue, Dec 30, 2018
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  10. Dec 30, 2018 at 10:30 AM
    #30
    cruiserguy

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    cruiserguy Well-Known Member

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    That's what I was getting at, replaced it without truly diagnosing the issue. Happens all the time. I was agreeing with you, I think. Lol
     
    cruiserguy, Dec 30, 2018
    #30
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  11. Dec 30, 2018 at 10:30 AM
    #31
    tacomainthesun

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    tacomainthesun [OP] Well-Known Member

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    :mad::censored:
     
    tacomainthesun, Dec 30, 2018
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  12. Dec 30, 2018 at 10:32 AM
    #32
    Bishop84

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    Bishop84 Well-Known Member

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    Haha :dancingbacon:
     
    Bishop84, Dec 30, 2018
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  13. Dec 30, 2018 at 3:25 PM
    #33
    rogerman

    #33
    rogerman Well-Known Member

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    I have the P0420 code right now. My truck is a CA emissions but I live in Hawaii and there is no emission testing. If I were to buy non CARB cats, would it make the P0420 code go away? I've been looking around some people say that non carb cats on CA trucks still trigger the P0420 code.
     
    rogerman, Dec 30, 2018
    #33
  14. Dec 30, 2018 at 3:32 PM
    #34
    eon_blue

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    eon_blue Okayest Member

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    Hmm that's a good question I dont know for sure, I want to say there shouldn't be a difference as far a the ecu is concerned...But there could be. I know there's know difference in o2 sensors between different emission spec trucks so I don't know why the cats would be any different.
     
    eon_blue, Dec 30, 2018
    #34
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