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Infamous P0420 CEL code

Discussion in '1st Gen. Tacomas (1995-2004)' started by willtotheumm, Aug 16, 2010.

  1. Aug 16, 2010 at 6:43 PM
    #1
    willtotheumm

    willtotheumm [OP] Yo Taco!

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    K&N intake. That is all. For now...
    Hey guys. I popped a CEL the other day in my Tacoma. I scanned it today and it showed a P0420. I did a search and found a lot of results. Must be pretty common? :p

    A few of the results suggested to check the o2 sensor's and the cat's. I waited for the truck to cool and crawled under it. I removed the rear o2 sensor first. I found this:

    [​IMG]

    I figured it was just normal coloring. The truck has 106xxx on it.

    After that I removed the front o2 sensor and found this:

    [​IMG]

    Looks like it was replaced not too long before it was purchased. Sweet.

    I have a stock exhaust (for now) and still have my cat's. I figure i'll replace the o2 sensor first and see if the code comes back. What do you guys think?
     
  2. Aug 16, 2010 at 6:48 PM
    #2
    willtotheumm

    willtotheumm [OP] Yo Taco!

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    K&N intake. That is all. For now...
    On Rockauto I found a few results for the rear o2 sensor.

    -Denso universal
    -Standard Motor Products
    -Denso OE style
    -Bosch OE type
    -Delphi
    -NTK
    -Airtex/Wells
    -AC Delco

    Anybody have good or bad experience with any of them?
     
  3. Aug 16, 2010 at 6:56 PM
    #3
    shitroc

    shitroc Master of War

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    Denso OEM replacements are what i installed and have had good luck with them. our trucks seem to dislike anything besides oem replacements like Bosch or Denso, i wouldnt bother with anything besides them(especially a universal sensor). its hard to tell by the pics whether the sensors need replacing or not,they most likely do. to find out for sure youd have to break out the multimeter, or just replace em and see. hopefully its not your cats is all i gotta say though,they can be pretty pricey.
     
  4. Aug 16, 2010 at 7:04 PM
    #4
    willtotheumm

    willtotheumm [OP] Yo Taco!

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    How do I test them with a DMM? That would certainly help make sure that the o2 sensor is the problem lol.

    Yeah as soon as I saw 'catalyst' I sighed. Getting a universal one for my old MR2 was $120 and that was before 1/1/09. I wouldn't want to see how much they'd go for for my Taco.
     
  5. Aug 17, 2010 at 2:12 PM
    #5
    shitroc

    shitroc Master of War

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    you need one with continuity, take an ohm reading between the two black wires. Bank 1 sensor 1 should read between 0.8 and 1.4 ohms. a bad sensor will have no continuity. IIRC. i think you can also get obd2 code readers that are able to test this kinda shit to.
     
  6. Aug 17, 2010 at 2:45 PM
    #6
    jesus

    jesus Well-Known Member

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    hey willtotheumm how many miles do ya have on your truck????
     
  7. Aug 17, 2010 at 2:46 PM
    #7
    jesus

    jesus Well-Known Member

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    hey if it ends up that you do need a cat look into magnaflow they now have a blot on.... and I think Autozone has it for a bit under $400
     
  8. Aug 17, 2010 at 3:55 PM
    #8
    iDigTulsa

    iDigTulsa Well-Known Member

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    Free Alarm Mod, Grey Wire Mod, Reverse Leaf Spring Helper Mod, Kenwood Deck, Memphis 10'', Yakima Roof Rack, Debadged Sides,Silver Toyota Skid Plate, Injen CIA, 3.5'' Amsoil Dry Filter, 17 x 7.5 Tundra Split Spoke Alloy's
    RockAuto.com has some of the best prices when it comes to things like this, I would check them out too.

    I've not found anything they couldn't beat the price on from one of the local auto parts stores. BUT...I only use them when I don't have to have the part immediately, since it has to be shipped.

    http://www.rockauto.com/catalog/raframecatalog.php
     
  9. Aug 17, 2010 at 7:37 PM
    #9
    willtotheumm

    willtotheumm [OP] Yo Taco!

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    K&N intake. That is all. For now...
    Well I found an OEM style Denso for $65.71 shipped. Part number 234-4189.

    The weirdest thing happened today. CEL was on on my way to work this morning, and on the way home 8 hours later. I relaxed at home and 2 hours later went to leave. No more CEL. Drove all over town and still no CEL. My mileage didn't seem effected either. Hmm...

    The truck has 106xxx on it.
     
  10. Aug 17, 2010 at 10:39 PM
    #10
    jesus

    jesus Well-Known Member

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    man I hate to say it but you may start thinking about the cat:(
     
  11. Aug 18, 2010 at 3:38 PM
    #11
    shitroc

    shitroc Master of War

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    ^ why do you say that, because of mileage?106k isnt much at all
     
  12. Aug 20, 2010 at 7:24 PM
    #12
    vapovick

    vapovick Active Member

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    hi, just had a similar issue P0136 I blew both O2 sensors... turned out my exhaust manifold cracked. Cold air was being sucked in over the sensors and blew them, might want to also check for leaks. My rear sensor looked like coal. Hope this helps.
     
  13. Aug 25, 2010 at 7:31 PM
    #13
    willtotheumm

    willtotheumm [OP] Yo Taco!

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    K&N intake. That is all. For now...
    Thanks for all your help guys. But the CEL hasn't come back so i'll be paying close attention to it. Gas mileage is back to normal too.

    I'm not sure if maybe a slightly shook something loose in one of the o2 sensors? Or maybe one of them has a loose wire? I'm not sure. But once the light comes back, if it does, i'll bump this thread with an update. :)
     
  14. Aug 25, 2010 at 7:50 PM
    #14
    memario1214

    memario1214 Vivid Illumination Vendor

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    The problem you very well may have is that your front cats shit the bed... I have 86k on my truck and when I took out my rear cats recently, I found pieces of the screen from the front ones in them. About 2 months ago I threw the PO420 code. I'm sure its not my sensors and that my cats see just destroyed...
     
  15. Nov 10, 2010 at 12:54 PM
    #15
    el contrador

    el contrador Member

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    Original a to z
    It's been a few months since your last post, did the light come back on???
     
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