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Code P0420 catalytic converter

Discussion in '1st Gen. Tacomas (1995-2004)' started by Zac, Sep 1, 2009.

  1. Sep 1, 2009 at 10:47 PM
    #1
    Zac

    Zac [OP] Member

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    Im getting this code and i think it is why im not passing emissions, i just had a universal catalytic converter put in a little over a year ago. Does anyone have any ideas on where this code is coming from and what to do to fix it?
     
  2. Sep 2, 2009 at 8:00 AM
    #2
    Skolfoppa

    Skolfoppa Member

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    Rear O2 sensor.
     
  3. Sep 2, 2009 at 4:32 PM
    #3
    Zac

    Zac [OP] Member

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    When i had the diagnostic plug in my O2's befor the cat and after were reading the same numbers, So do you think that they both might be bad?
     
  4. Sep 2, 2009 at 8:20 PM
    #4
    98tacoma27

    98tacoma27 is gooder 'en chicken Moderator

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    Your O2 sensor should be fine. It's your universal CAT that is bad.
     
  5. Sep 3, 2009 at 11:33 AM
    #5
    Zac

    Zac [OP] Member

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    so do you suggest not buying another universal cat do those seem to just crap out. and does it matter that the guy welded it in ?
     
  6. Sep 3, 2009 at 11:41 AM
    #6
    98tacoma27

    98tacoma27 is gooder 'en chicken Moderator

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    Imports tend not to like the universal or aftermarket CAT's. Did the code just come up recently? How often do you have to do emissions checks?
     
  7. Sep 3, 2009 at 2:13 PM
    #7
    trailinTaco

    trailinTaco Well-Known Member

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    i got the same code. it goes on and off alot. Im really hoping and thinking its the rear o2 heater sensor not the cat.
     
  8. Sep 3, 2009 at 5:31 PM
    #8
    Siebler

    Siebler Duck Killing Machine

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    How many miles are on your truck and have you ever replaced the O2 sensors?

    I threw the same code this last week but refuse to believe its my cat and am thinking O2 sensors. After all I do have 115k on the original sensors.
     
  9. Sep 3, 2009 at 5:35 PM
    #9
    98tacoma27

    98tacoma27 is gooder 'en chicken Moderator

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    You will get a code for bad sensor.
     
  10. Sep 7, 2009 at 12:09 PM
    #10
    Zac

    Zac [OP] Member

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    No i have NEVER replace either O2 sensor. i have around 125k miles and the code came up last year abunch and then i could not pass emissons last year thats why ibought the cat in the first place. then as soon as it was time to renew my tags this april the damn P0420 code came back up.
     
  11. Sep 7, 2009 at 12:26 PM
    #11
    KenpachiZaraki

    KenpachiZaraki Its Wicked Flow BITCHES!!

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    p0420 or p0430 is either the cat or the o2 sen. There's no way to tell exactly, except running a diagnostic on your vehicle, for which you'll get charged 70-80 bucks. Thats the only way you're gonna know exactly what it is. This is the Autozone talk i have with my customers sometimes:D
     
  12. Sep 7, 2009 at 4:36 PM
    #12
    Zac

    Zac [OP] Member

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    did you end up changing the O2 sensor after all, and if yeas did that p0420 code go away
     
  13. Sep 8, 2009 at 10:24 PM
    #13
    Siebler

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    I cleared the code last week right after it showed up but wont get around to changing the sensor until Sunday when im installing my Oil Bypass system. So far the code has not come back though.

    My fuel economy is below average though. Going to get the new sensor in and see what happens.
     
  14. Sep 9, 2009 at 6:52 AM
    #14
    98tacoma27

    98tacoma27 is gooder 'en chicken Moderator

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    Yeah, let us know what you come up with and good luck.
     
  15. Sep 9, 2009 at 11:19 PM
    #15
    sansaelee925

    sansaelee925 New Member

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    I have the same problem, I kept getting the P0171, finally changed my front o2 sensor (OEM from Toyota). I live in Sacramento, as soon as I replaced the front o2 sensor, I drove to reno. When I came back a day later, my CEL came on as soon as I pulled up on the driveway. I plugged in my OBDII code reader, and got the P0420. I'm waiting on my rear o2 sensor right now, I was told that I was suppose to replace both of the o2 sensors at the same time (something about how they read, the older one will read slower). I'm not sure if that's true or not but, be prepared to replace your front o2 sensor soon after (if what I was told is true).
     
  16. Sep 10, 2009 at 5:50 AM
    #16
    98tacoma27

    98tacoma27 is gooder 'en chicken Moderator

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    That is not true.
     
  17. Sep 10, 2009 at 6:15 AM
    #17
    jfr02

    jfr02 Well-Known Member

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    i have seen that code more times than i can count.never once did an 02sensor fix the issue.not saying that it won't but it is a bit unlikely.if it is the sensor 99% of the time there will be a code for the sensor.you realy need to get it diagnosed.if you can get a scan tool you need to look at the o2 perameters watch the number while the car is running in open loop.if one of the sensors number are changing slow or not at all that's you bad sensor.those numbers should be jumping all over the place.i hope this helps alittle.
     
  18. Sep 10, 2009 at 10:13 AM
    #18
    Siebler

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    Ill watch the numbers on my way to work and see whats happening.
     
  19. Sep 10, 2009 at 3:13 PM
    #19
    Zac

    Zac [OP] Member

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    Jfr02-- Hey I did read my o2 sensors the the front and the back sensors were reading the same Numbers. COuld it be the universal CAT or do you think that it could just be the o2 sensors? please help, im like 6 months past my emissions date.
     
  20. Sep 10, 2009 at 3:40 PM
    #20
    jfr02

    jfr02 Well-Known Member

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    i would assume it is the cat.the post cat sensor would be the one to look at.depending on the price of the sensor you could just put it in and hope for the best.now are the numbers changing rapidly,slow,or not at all.it's hard for me to be positive without the service manual or seeing things for myself.one other thing to look for is your cat getting very hot,is it glowing after running for a while.hit the cat with a mallet and listen for it rattling.oh i forgot with the scan tool there is a part where you can look if your running lean or rich youll know when you find it it will switch back and forth between rich and lean.i'm not sure where to find it on toyota's sorry i'm not more help
     
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