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Trouble code P0420

Discussion in '1st Gen. Tacomas (1995-2004)' started by el contrador, Oct 25, 2010.

  1. Oct 25, 2010 at 1:54 PM
    #1
    el contrador

    el contrador [OP] Member

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    Hi, I'm new on Tacoma World,

    I own a 2003 Tacoma, Double cab, 3.4L, 4wd and an my check engine light cam on last weekend :( but the truc runs perfectly... :confused:

    the code is P0420

    "Repair information" P0420 - Catalyst System Efficiency Below Threshold (Bank 1)

    Since the Cat and o2 sensors are very expensive I wouldn't want to change the part for nothing.

    Did any body had this code and if so, what did you do to fix it!!??

    thank you
     
  2. Oct 25, 2010 at 2:41 PM
    #2
    stucksucksnayota

    stucksucksnayota Well-Known Member

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    I have the same code and I'm in the same boat your in. I have heard that it is a O2 sensor and a fuel/air mixture sensor. I have heard that you can buy a generic O2 sensor and just wire it in but sense it is also supposed to be a fuel/air mixture sensor I don't know if you can.
     
  3. Oct 25, 2010 at 3:50 PM
    #3
    shitroc

    shitroc Master of War

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    the cat and the o2 sensors would definitly be where to start, if you decide to replace ur o2 sensors you should do both at the same time. the prices at rockauto.com arent to pricey and you get a TW member discount IIRC. get a OEM replacement (denso,bosch). or if ya want you could buy a URD simulator it is meant to turn off the CEL when you get a P0420 code, although its more meant for people who run no cat or a high flow cat.
     
  4. Nov 27, 2010 at 8:04 AM
    #4
    el contrador

    el contrador [OP] Member

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    Hi!!

    I've been reading A LOT on this P0420 problem and found out a few good thing you might like to know!!!

    I lot of people have the same problem that we do, some changed everything related to emission system. Cats, o2 sensors, MAF, MAP, Temperature Sensor and still had the light coming on!!

    On thing that not a lot a people think of checking is the Ethanol rating in the gasoline they use!! Toyota tacoma are set to use Gas with less then 10% ethanol... So what i did is I empty my tank and filled it back with ethanol Free Gasoline, unplug the battery to erase the codes and Guess what, no more light...

    The problem with ethanol is that it doesn't burn like regular gas at all and our O2 sensors do not reconised the exhaust gas so your check engine light turn on!!!

    I was using Gasoline that had 12% Ethanol and didn't know it!!

    Try that and let me know what happens

    Thanks
     
    johnny3 and fireman1073 like this.
  5. Nov 27, 2010 at 8:38 AM
    #5
    kingston73

    kingston73 Well-Known Member

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    I had this code and it turned out to be a leak in the exhaust system, I just had to tighten the joint between the cat and the back of the exhaust. That's the first I've heard of ethanol causing the code, unfortunately many people don't have the luxury of choosing non-ethanol gas.
     
  6. Mar 1, 2011 at 5:19 PM
    #6
    stucksucksnayota

    stucksucksnayota Well-Known Member

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    I think the gas idea may be along the right track. I used to buy my gas from a station that always had the cheapest gas which I'm guessing is probably because they use more ethanol in the gas.

    My light would come on and I'd get it turned off then it would come on and I'd turn it off. So I seafoamed it and started running gas from a different station with "supposable" better quality gas and my light hasn't come on since. Knock on wood.
     
  7. Mar 1, 2011 at 8:30 PM
    #7
    davestaco

    davestaco TW's number one gear whore

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    I have the same problem and i think i know the fix. Our 1st gens. i bellieve have 2 cats. one at the headers and one down the pipe a little bit. The code is a o2 code but you will never know which cat and o2 is causing it. I was told that you can cut both cats out and put one longer one in its place, then wire up one new o2 censor. any thoughts?
     
  8. Mar 1, 2011 at 9:12 PM
    #8
    malander

    malander That's some tight butthole

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    It's almost always the sensors. Do em both at the same time and get denso oem styles. Bosch will not work correctly, I found that out the hard way and still have one laying around somewhere. I've never replaced the front o2 sensor but the rear one is really easy *if* the old sensor isn't rusted into the bung.
     
  9. Mar 1, 2011 at 9:22 PM
    #9
    dustinclm

    dustinclm Well-Known Member

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    i have the same code, but i also dont have my second cat and my URD simulator should be here by friday so that should fix it. it could also be a leak, for the longest time now i have heard a "puffing" noise on curbs, walls or any obstruction when i pass but can not for the life of me find it. i have checked, check, re checked, brought it to a muffler shop and still cant find the leak...its driving me nuts, it seems i only hear it when im hitting the gas so maybe thats why i cant find it when i look when its idling....
     
  10. Mar 2, 2011 at 12:50 PM
    #10
    Skillet

    Skillet Well-Known Member

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    Only factory o2 sensors for me found out the hard way,(don't buy from vato zone ever!) denso should be what you want for sensors.
     
  11. Mar 2, 2011 at 9:18 PM
    #11
    davestaco

    davestaco TW's number one gear whore

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    run some seafoam through the brake booster. i bet you find it then:D
     
  12. Mar 3, 2011 at 10:35 AM
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    dustinclm

    dustinclm Well-Known Member

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    i did that but i didnt think of looking for the leak and i did it myself, ill get a buddy to help me and norrow down next time i get some time to mess with it
     
  13. Mar 4, 2011 at 6:47 AM
    #13
    el contrador

    el contrador [OP] Member

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    Finally the problem was only an exhaust leak. The flange gasket between the second Cat and the extension, right before the second O2 sensor was finish. I replaced it, erase the codes and voila!! done... the check engine light is off since 2 month now...

    The reason the check engine light goes on with P0420 code is because when you are driving at a constant speed, the flow in exhaust creates a vacuum and pull fresh air from exterior by the hole and falls the o2 sensors reading...

    Verify leaks by blocking muffler and check for very small leaks, specially near o2 sensors!!
     
  14. May 31, 2016 at 11:50 AM
    #14
    thumper72

    thumper72 Well-Known Member

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    Well went to AutoZone and found out I have a code (po420) he said I have possible bad gas or a hole in my cat! Recommended fuel injector cleaner and a octane booster? I m thinking gas as I just filled up 50 miles ago from almost empty....
     
  15. May 31, 2016 at 12:11 PM
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    127.0.0.1

    127.0.0.1 AKA ::1

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    if you have 130,000 mile or more and it's the OEM sensor, it's likely the sensor itself that crapped out

    they do wear out
     
  16. May 31, 2016 at 12:30 PM
    #16
    thumper72

    thumper72 Well-Known Member

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    I'll look into it lol I have 230k lol how would you tell.if OEM or not clipped wires?
     
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