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 don’t see anything else. I doubt it’s a pressure valve or breather valve


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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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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 ��

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Originally Posted by Eg.h2o

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 ��

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Yes I’ve read about using an o2 extender but wasn’t 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 I’ll be replacing the fuel pump real soon and injectors because I work at a junk yard and use the gas we drain from cars [emoji28]


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Quote:

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Originally Posted by Bra1nDamag3d

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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I have replaced a lot of wiring and plugs on top of the motor and underneath cracked with slight corrosion


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Quote:

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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. :p

Quote:

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Originally Posted by Eg.h2o

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. :p

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Maybe I’ll swap out the injectors and fuel pump and see what happens from there


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Quote:

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Originally Posted by Eg.h2o

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. :p

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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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