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Thread: 2.2 L61 Code P0421 - 2004 Cavalier

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    2.2 L61 Code P0420 - 2004 Cavalier

    Ok new issue....

    Last week I threw a CEL that started flashing when I drove the car. P0300 random multiple cylinder misfire. I replaced the Ignition Control Module and cleared the code. Car ran fine.

    Same day about 25 miles later I threw another CEL. This time I pulled P0420 Catalyst Effeciency Below Threshold Bank 1. I cleared the code, drove it for about 95 miles and 3 days, just got the light again so I'm assuming it's the same thing.

    I've been searching and reading... O2 sensors or a bad cat is what I've come to gather. The car's only got 43k on it and this just started happening after the ICM went out so I'm not gonna start throwing money at it until I find out where the problem really lies. I want to test the O2 sensors before replacing, but I'm not sure how. Would a normal voltmeter read it? Where do I physically test them at?

    What other options do I have? I just find it hard to swallow that if your ICM acts up then it starts other problems... I only drove it a half mile back to my house with it running bad.

    Throw me a frickin' bone here?

    PS. My inspection is due today 1/31... These things always seem to happen at the best of times right?
    Last edited by dannythekid; 01-31-2008 at 10:39 AM.

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    clear the code again take it out and beat the piss out of it and see if it throws the code again. also it well help set the im readiness so if it doesnt throw the code you will pass inspection

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    Sorry I edited the OP... I did clear the light and got it a 2nd time. Both times the light comes on at idle.

    I'm pretty sure I'm just gonna clear the code, get it inspected, then worry about it when it's not 20* outside.

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    What state are you getting it inspected in, depending on how they do their test if they just plug in a obdII reader they are going to get a not ready code when you get it inspected. If they put a sniffer in the tailpipe you might be ok. Do you have a high flow cat or is your exhaust stock? There is a cheap fix involving 2 spark plug anti foulers being plugged into your rear o2 sensor bung and then screwing the sensor into the anti foulers that will get rid of your code. I had the same code as you for a long time and did this trick and has been off for about 7 months now.

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    I'd rather fix it then get the anti-foulers, but if that comes down to it then I will... Just would like to know what's making it happen.

    I live in Pennsylvania, and I think they just use a sniffer. I'm going to pull my spark plugs (Bosch Platinum +2) which seem to be the issue from my ICM and maybe even this, then get a new O2 eventually.

    I'll probably just clear the code right before I get it inspected.

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    I'm from PA too, they hook up a computer to read codes. Which county are you in? Not all of them do emissions inspections.

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    Allegheny, where they charge tax for poured drinks.

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    First of all a P0420 is almost never an oxygen sensor, 99.44% of the time it is the catalytic converter.

    The P0420 actually lets you know that the O2 sensor is working.(this code is set by the rear/aftercat O2 sensor by the way)

    The flashing MIL tells the story, catalytic converter damaging misfire.

    If youve got a 2004 with 43,000 miles your catalytic converter is still under warranty. Head to the dealer to get a free cat.
    Last edited by maven; 01-31-2008 at 09:25 PM.
    I know stuff about ECOTECS

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    Allegheny here too. If its under warranty go for the new cat, if not the cheapest fix is going to be the spark plug anti foulers like I mentioned. Kind of weird for it to throw this code if your using the stock cat, did you have any exhaust work done to your car?

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    No, the car is bone stock besides the Bosch plugs, which baffles me...

    And I hardly drove the car with it misfiring. Just enough to get it back to the house. No more than half a mile. What a joke.

    I'm gonna call the dealer tomorrow and see if they wanna check it out. I HATE dealers and trust them the least out of all mechanics. But if I can get it done under warranty I'll do that.

    Thanks maven.

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    Well I sucked it up and took it to the stealership. Paid the diag fee and it's a cat fault...

    However, they won't replace the cat under federal 8/80 warranty because my car is an R title (for a nonsense reason too). So it looks like I'll be strapping a universal cat on there to get it inspected.

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    Well I sucked it up and took it to the stealership. Paid the diag fee and it's a cat fault...

    However, they won't replace the cat under federal 8/80 warranty because my car is an R title (for a nonsense reason too). So it looks like I'll be strapping a universal cat on there to get it inspected.
    dannythekid Quoted Post

    Whats an "R" title, you have to do something pretty f'd to void a federally mandated warranty.
    I know stuff about ECOTECS

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