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Re: GM dealer says P0420 caused by downstream sensor. What say you?
Posted to Technical Discussion Forum on 3/9/2007 4 Replies

Hi Rick,

I just did a pair of front O2 sensors on an Explorer for a cat code, but a rear sensor?

I'd be hard pressed to come up with a feasible scenario for a rear sensor failure flagging a false Cat code, but I'm sure that someone else here will educate u... Login to read more.

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