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20024runner

Discussion in '3rd Gen 4Runners (1996-2002)' started by Jkpt445, Dec 2, 2021.

  1. Dec 2, 2021 at 11:50 AM
    #1
    Jkpt445

    Jkpt445 [OP] New Member

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    Hello mew here looking for a little help, I’ve been get 420 error code I’ve replace both 02 sensors repaired an exhaust leak and I can’t even get three cold starts with Che k engine light coming back on
     
  2. Dec 2, 2021 at 12:10 PM
    #2
    negusm

    negusm New Member

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    Error code P0420?

    Most 2002s uses an AF sensor and NOT an O2 sensor. Go to your TOYOTA dealer and buy the correct sensors by giving them your VIN. The dealer can tell you which combination of sensors you have by your VIN. No one else can.

    If you did replace your sensors with ones from the dealer, the CAT may be bad. Check thermal readings front and back. Back should be hotter if working.
     
    OverRunner likes this.
  3. Dec 2, 2021 at 12:37 PM
    #3
    Jkpt445

    Jkpt445 [OP] New Member

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    Thank you
     
  4. Dec 2, 2021 at 12:38 PM
    #4
    Jkpt445

    Jkpt445 [OP] New Member

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    Ok what’s the difference between AF sensor and O2 sensor
     
  5. Dec 2, 2021 at 12:51 PM
    #5
    jester243

    jester243 rabble rabble rabble

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    I changed some lights, tires and tinted windows...mind blowing huh
    i found this:

     
  6. Dec 2, 2021 at 1:58 PM
    #6
    Jkpt445

    Jkpt445 [OP] New Member

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    Thank you I didn’t know that and once I talked to my mechanic friends a light bulb went off
     
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  7. Dec 17, 2021 at 6:30 PM
    #7
    Jkpt445

    Jkpt445 [OP] New Member

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    Hello guys changed AF sensors and a week later threw 420 code again I’m pretty frustrated any ideas
     
  8. Dec 17, 2021 at 6:35 PM
    #8
    Mtbpsych

    Mtbpsych New Member

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    What did you change? Your AF/airflow sensor goes on the air intake manifold, and your O2 sensor goes along the exhaust system. If you replaced both sensors you could be having vacuum or EGR related issues.
     
  9. Dec 17, 2021 at 6:37 PM
    #9
    Jkpt445

    Jkpt445 [OP] New Member

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    I replaced both the Front AF sensor and O2 rear sensor on exhaust no one suggested the are AF sensor
     
  10. Dec 17, 2021 at 7:22 PM
    #10
    negusm

    negusm New Member

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    Not the MAF sensor, we're talking the AF exhaust sensor.

    2001/2002 (depends on the VIN) used different AF sensors instead of the O2 sensors.

    -Mike
     
  11. Dec 17, 2021 at 7:24 PM
    #11
    negusm

    negusm New Member

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    A few things...

    #1...did you buy from TOYOTA? Chinese sensors do NOT work for LONG.

    #2...did you rule out the catalytic converter? It may be bad. Check the temperature front and back. Make sure the temperature is correct (it should be higher AFTER the Cat Converter)
     
  12. Dec 18, 2021 at 1:03 AM
    #12
    Jkpt445

    Jkpt445 [OP] New Member

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    Yes went to Toyota got both front and rear sensors gave vin number to them
     
  13. Dec 18, 2021 at 1:52 PM
    #13
    negusm

    negusm New Member

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    Sounds like the cat is probably bad then.

    Now...there is a cheap thing you can maybe do to get rid of the code:

    https://www.youtube.com/watch?v=kzm52m0AWSQ

    Worth a try. After doing it, clear the code and pray.

    Also, what are your driving habits? These rigs are notorious to throw that code after highway driving. It happens on mine and I clear the code probably once a year.
     
  14. Dec 18, 2021 at 4:49 PM
    #14
    Jkpt445

    Jkpt445 [OP] New Member

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    It’s most likely the cat but I don’t have $900 to replace it I’ve heard about the sensor extend I’ll have to give it a try
     
  15. Dec 18, 2021 at 8:50 PM
    #15
    negusm

    negusm New Member

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    Did you check the before and after temps of the cat? An infrared thermometer is like $20.

    You should know where the problem really is.
     

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