98 Gen 2.5 CEL Code P0421

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98 Gen 2.5 CEL Code P0421 #1042018 02/15/12 03:11 AM

Joined: Feb 2008

Posts: 120

Phoenix, AZ

OneTime

Wheeler

I have a CEL light on with a code P0421. I remember the dealer telling me a while back it was either the #1 or the #2cat, I cant remember which. I pulled the code again at autozone and was given the P0421 "warm up catalyst effeciency below threshhold" Do I simply need to replace one of the cats or is something else going on?

98 Gen 2.5 w/ winter package & 31x10 BFG ATs.

Re: 98 Gen 2.5 CEL Code P0421 [Re: OneTime] #1042019 02/15/12 05:09 AM

Joined: Jan 2001

Posts: 13,649

Helen , GA

fasteddy

Web Wheeler

Thats a code for:

"Basically this means that the oxygen sensor downstream of the catalytic converter on bank 1 is detecting that the converter is not working as efficiently as it should be (according to specs). It is part of the vehicle emissions system."

I found a cheap fix that works on a 3g Eclipse, and may work for you at this site.

Also check for leaks in the exhaust system ahead of the final ohtwo sensor on bank 1. May be a bad ohtwo sensor too...

Not responsible for advice not taken...

Re: 98 Gen 2.5 CEL Code P0421 [Re: fasteddy] #1042020 02/17/12 05:04 AM

Joined: Feb 2008

Posts: 120

Phoenix, AZ

OneTime

Wheeler

Is there anyway for a mechanic to find out if the cat is bad or if its the O2 sensor?

98 Gen 2.5 w/ winter package & 31x10 BFG ATs.

Re: 98 Gen 2.5 CEL Code P0421 [Re: OneTime] #1042021 02/17/12 06:14 PM

Joined: Jun 2002

Posts: 6,211

Apache Junction, AZ

JohnnyBfromPeoria Offline

Trail Leader

If the cat is bad the inlet and outlet temperatures will be vey close to the same. If it's good, the outlet temps will be higher than the inlet. Use a non-contact thermometer to check. Harbor Freight sells them.

John B.