P0420/p0430

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Feb 4, 2011 | 10:33 AM

SSGT's99vette

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From: Jacksonville NC

P0420/p0430

I have both of these codes on my 96, what would cause them both to come on. both catalyst are below threshold. Can anyone help on this matter??? The main reason for asking is the car has 69,500 and I find it hard to believe that both CAT's would go bad at the same time.

Last edited by SSGT's99vette; Feb 4, 2011 at 11:18 AM.

Feb 4, 2011 | 12:18 PM

0Paul Ruggeri

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Joined: Nov 2006

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From: Carmichael ca

Its possible the cats are bad. Its also possible the O2 sensors are bad. I'd clear the codes and run it for awhile and see if the codes come back.

Feb 4, 2011 | 12:56 PM

dogfish246

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From: North New Jersey

Quote:

Originally Posted by Paul Ruggeri

Its possible the cats are bad. Its also possible the O2 sensors are bad. I'd clear the codes and run it for awhile and see if the codes come back.

My PO420 comes on for the drivers side cat every once in a blue moon... Its either my cat on its way out or an O2 sensor. Not a big deal. I just reset the code and have no problems... If your OBDII reader is also a scanner you can scan the O2 sensors to see if they are working...

Feb 4, 2011 | 06:59 PM

M. Schumacher

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The wiring harnesses to the O2 sensors run very close to the exhaust. Have you been down there doing any work?

Feb 7, 2011 | 03:10 PM

SSGT's99vette

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From: Jacksonville NC

No this car is completely stock, the wiring is in tact, and I reset the codes and within 15 miles they come right back on.

Feb 7, 2011 | 03:22 PM

Bronze85

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From: Vernon Hills Ill

The cats are definitely bad. The codes set when the pre and post cat O2 sensors are mirroring, meaning the cat is not doing its job. The post O2 sensor should have hardly any voltage activity.