P0420 code ?? - Chevy Impala Forums
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post #1 of (permalink) Old 09-09-2009 Thread Starter
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P0420 code ??

Well by my screen name you can tell I'm not a RM owner. But my dad is. Actually he wants to let my son use his 96 RM untill he can afford his own car. Good shape. Almost 98K on it. But keeps throwing a P0420 code. O2 sensor is ok so I guess it's the cat. Was considering gutting the cat and using an O2 simulator to kill the CEL. Anyone else doing this ???
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post #2 of (permalink) Old 09-09-2009
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On 96 and newer vehicles you will find that the gas mileage will suffer if you delete/gut the cat. Best thing is to bite the bullet and replace the cat.

Emulators do not always fool the PCM, especially the OBD-II systems.


1977 Chevrolet Impala Sedan
1989 GMC C1500 Sierra ECSB

Last edited by 77Impala; 09-09-2009 at 03:43 PM. Reason: correction
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post #3 of (permalink) Old 09-10-2009
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Also just to add my .02

If you don't have the money available to replace a cat, also try this. The converter might just have some crud built up in it that's killing efficiency. That code indicates a general inefficiency.

Go for a drive where you will be able to drive for at least an hour at the speed limit. Turn on your AC, crank the fan and roll all the windows down. This will make the engine work harder and will thus get hotter. A hotter engine will (duh) produce hotter exhaust and will be hot enough to burn any extra crud out.

You'll burn a few gallons of unleaded but it's a lot cheaper than a cat and it worked on my car!
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post #4 of (permalink) Old 09-10-2009 Thread Starter
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Originally Posted by cbmikey View Post
Also just to add my .02

If you don't have the money available to replace a cat, also try this. The converter might just have some crud built up in it that's killing efficiency. That code indicates a general inefficiency.

Go for a drive where you will be able to drive for at least an hour at the speed limit. Turn on your AC, crank the fan and roll all the windows down. This will make the engine work harder and will thus get hotter. A hotter engine will (duh) produce hotter exhaust and will be hot enough to burn any extra crud out.

You'll burn a few gallons of unleaded but it's a lot cheaper than a cat and it worked on my car!
Thanks. Been there done that. Gutted the cat last night and runs 1000% better and no codes. I'll probably end up putting in a new cat but not at this time.
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post #5 of (permalink) Old 09-10-2009
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Originally Posted by 67 455 Bird ragtop View Post
Thanks. Been there done that. Gutted the cat last night and runs 1000% better and no codes. I'll probably end up putting in a new cat but not at this time.

Good deal. Several time we have found the cat/s to be coming apart, some so much they literally almost shut the car off from restriction. Sometimes gutting will work, sometimes it wont.
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post #6 of (permalink) Old 09-10-2009
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Gutted the cat last night and .... no codes.
It will generate a code soon. If you reset the PCM after gutting the cat then it will take a few drives for the PCM to detect that the cat is not doing its job.


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post #7 of (permalink) Old 09-11-2009 Thread Starter
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It will generate a code soon. If you reset the PCM after gutting the cat then it will take a few drives for the PCM to detect that the cat is not doing its job.
Yep .. took about 20 minutes of driving . But, that's the only code now. This is actually my dad's car and he's letting my son use it for a while. Well probably either put a new cat in later or an O2 simlator. Not sure which yet. But it is driving MUCH better now.
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post #8 of (permalink) Old 09-12-2009
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wow you made money with this topic, not just being a cheap ass and hollowing the cat, but you made .04 cents. Dude, that's sweet
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post #9 of (permalink) Old 09-12-2009
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A CEL set by a rear O2 will NOT affect performance or economy. Deleteing the cats(if functional) will NOT have any meaningful effect on performance or economy either. Your solution of hollowing a plugged one wont hurt anything unless you got caught by some freak chance.

Dwayne
96 Caprice with AI 200cc package
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post #10 of (permalink) Old 09-14-2009
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Originally Posted by Dwayne J View Post
A CEL set by a rear O2 will NOT affect performance or economy. Deleteing the cats(if functional) will NOT have any meaningful effect on performance or economy either. Your solution of hollowing a plugged one wont hurt anything unless you got caught by some freak chance.
Isn't that highly illegal...to gut a cat?

Serious question as I've never been required to pass any kind of e-check or inspection.
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post #11 of (permalink) Old 09-14-2009
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Originally Posted by cbmikey View Post
Isn't that highly illegal...to gut a cat?

Serious question as I've never been required to pass any kind of e-check or inspection.
Yes it is though if your vehicle is not in an emission testing state or county then the inspection places will not notice.


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post #12 of (permalink) Old 09-14-2009
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Quote:
Originally Posted by Dwayne J View Post
A CEL set by a rear O2 will NOT affect performance or economy. Deleteing the cats(if functional) will NOT have any meaningful effect on performance or economy either. Your solution of hollowing a plugged one wont hurt anything unless you got caught by some freak chance.
illegal at the federal level even if your state has no inspection. Also done every day of the week in every state of the union.

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post #13 of (permalink) Old 09-15-2009
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Cat guts make the best fish bait

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