Cat Bad? P0420 code

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Jun 21, 2004 | 02:43 PM

DoraDexplora

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Cat Bad? P0420 code

I have a 96 Explorer (6 cyl 110k miles) with a check engine light on, Pep Boys says the cat is going bad but my mechanic says its the O2 sensor. Any way to figure out who is right?

Much appreciated

Jun 21, 2004 | 03:03 PM

ranger88a

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P0420 is a catalyst below efficiency code. You probably have a cat going bad. The code tells me the sensor works, and that the cat doesn't do it's job. I have however had a problem with some aftermarket cats, they don't seem to do the job well. Fords cats work, but are very expensive. Try looking for a reputable exhaust dealer who will stand behind their work.

Jun 21, 2004 | 04:58 PM

87 XLT

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From: SoCal

I agree, sounds like a bad cat.

Jun 22, 2004 | 07:51 AM

DoraDexplora

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Will do, Monroe makes a bolt on Cat for $500, half what Ford wants for theirs.

Thanks for the direction.

Jun 30, 2004 | 05:47 PM

91-Exploder

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There is a TSB available for this problem I had it on my 96' exploder

PCM - MIL ON DTC P0420 Stored in Memory TSB 00-26-4

You need to have your PCM recalibrated with a updated calibration file
the one the TSB recommends for 49 state cars is 6-58B-R10

This is a dealer job should be about $75-100 Much cheaper than a new cat
if this does not fix the problem you will need a new cat

Nov 22, 2004 | 07:04 PM

jbenazzi

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I have found the same thing . . .

I spoke with a Ford mechanic this morning . . . I told him my 1996 Explorer (116K miles) was showing the P0420 "catalyst below efficiency" code. I asked him what that meant (not mentioning that I had researched it here). He told me that it probably meant that I needed a new cat. I then told him that I had heard about the technical service bulletin from Ford about recalibrating the Powertrain Control Module (PCM). He had never heard of the TSB but when he came back he told me, "you definitely do not want to replace your cat, you DEFINITELY want to have your PCM recalibrated first." He said that, more than likely, he thought the recalibration would solve the problem (I really really really hope he is right).