p0420 question

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Nov 29, 2009 | 11:28 AM

NWASSEi

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From: NW Arkansas

p0420 question

Is that always a cat failing? Need to know before I spend the money on a new exhaust system next week?

Thanks

Don

Nov 29, 2009 | 11:33 AM

Purplehazeir

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From: Arlington, WA

It can mean a cat failing, engine coolant sensor, exhaust manifold leak or an O2 sensor. See https://www.gmforum.com/t284086/#post1390979

Nov 29, 2009 | 11:50 AM

NWASSEi

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From: NW Arkansas

Thanks, I will have the 02 sensor scanned before I replace the exhaust. I don't think it is an exhaust manifold leaking.

Don

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