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    Thread: Anyone experienced a P0420 catalyst low efficiency code???

    1. #1
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      Anyone experienced a P0420 catalyst low efficiency code???

      I randomly got a code the other day after replacing clutch. New maf and o2 sensors. Lean code p0171 as well did smoke test last night only leak came from rear of car where a hose goes into the body frame rail near the evap canister but I have no idea what the hose goes to and donít see anything else. I doubt itís a pressure valve or breather valve


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    2. #2
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      Sounds like you might be about to get the code p0449 as well
      The wiring that goes to the vapor canister behind the pass rear wheel is known to fail due to its location. Run new wiring and the p0171 should go away. As for the p0420, i had it and changes my upstream o2 sensor n it hasn't returned.

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    3. #3
      2004 1.6 Auto Rust Free
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      With over 350,000mi on mine, I had the 420 code come up and couldn’t fix it even with replacing the o2 sensors (I knew they were still good, but cheap to replace), and the cat (cali compliant). No leaks detected with the smoke machine.

      So I ended up cheating.

      $13.12 46% Off | Oxygen Sensor Extender, 90 Degree, 02 Bung Extension, Catalytic Converter, Universal O2, Sensor Spacer, New
      https://a.aliexpress.com/_mM8uTxe

      light is off now ��

    4. #4
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      Quote Originally Posted by Eg.h2o View Post
      With over 350,000mi on mine, I had the 420 code come up and couldnít fix it even with replacing the o2 sensors (I knew they were still good, but cheap to replace), and the cat (cali compliant). No leaks detected with the smoke machine.

      So I ended up cheating.

      $13.12 46% Off | Oxygen Sensor Extender, 90 Degree, 02 Bung Extension, Catalytic Converter, Universal O2, Sensor Spacer, New
      https://a.aliexpress.com/_mM8uTxe

      light is off now ��
      Yes Iíve read about using an o2 extender but wasnít trying to go that route yet lol. I will do a smoke test for the valve cover and what not. O2 sensor (v) for s1- (0.100-0.800) s2- (0.085-0.700). But Iíll be replacing the fuel pump real soon and injectors because I work at a junk yard and use the gas we drain from cars


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    5. #5
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      Quote Originally Posted by Bra1nDamag3d View Post
      Sounds like you might be about to get the code p0449 as well
      The wiring that goes to the vapor canister behind the pass rear wheel is known to fail due to its location. Run new wiring and the p0171 should go away. As for the p0420, i had it and changes my upstream o2 sensor n it hasn't returned.

      Sent from my SM-F936U using Tapatalk
      I have replaced a lot of wiring and plugs on top of the motor and underneath cracked with slight corrosion


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    6. #6
      2004 1.6 Auto Rust Free
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      Quote Originally Posted by Yes I’ve read about using an o2 extender but wasn’t trying to go that route yet lol.



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      I don’t blame you. I don’t like using cheats either, but I did all I could to figure it out. I gave up.

    7. #7
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      Quote Originally Posted by Eg.h2o View Post
      I donít blame you. I donít like using cheats either, but I did all I could to figure it out. I gave up.
      Maybe Iíll swap out the injectors and fuel pump and see what happens from there


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    8. #8
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      Quote Originally Posted by Eg.h2o View Post
      I donít blame you. I donít like using cheats either, but I did all I could to figure it out. I gave up.
      Hey, figured it out all my monitors are good now no codes since Saturday. I pulled my injectors. They were actually pretty dirty a lot of carbon buildup and gunk on them. I ended up, swapping them out from another Aveo that I have. And I re-gapped my plugs to .44


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