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I get OBD code 421. I have repalced everything except teh Cat Converter. The Eclipse has two converters. I am not sure which one to replace?

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SOURCE: catylitic converter

without a doubt, a plugged converter or your engine is still running rich. Any CEL Codes?

Posted on Sep 14, 2008

  • 6 Answers

SOURCE: check engine light

did you ask the dealer if the car an an emissions recall for this problem

Posted on Nov 13, 2008

  • 82 Answers

SOURCE: Cat-Converter-Is it necessary to make car run good?

you only need the converter if you live in an emissions state and have to pass inspections. Won't pass without it

Posted on May 05, 2009

  • 466 Answers

SOURCE: getting po104 reading on yhe


Posted on Dec 19, 2010

  • 2019 Answers

SOURCE: A recent scan indicated the

These are all transient symptoms, so I would not panic.
What I would suggest is putting in a tank of premium and fuel dryer.
A little water or cheap low octane gas can cause these symptoms.

If it happens again, a second try would be plug wires, because crossover in the wires will also do it.
Reducing plug gap will also make problems like this less noticeable.
You can go as low as .028".

Start with the cheap tries first, then worry about the more expensive things.

Posted on Jan 21, 2011

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1 Answer

1998 Ford Econoline has code p2099 what does it mean

code p 2099 refers to post cat converter fuel trim (FT) bank 2 --too rich===causes --catalytic converter
it also refers to engine coolant temperature (ECT) sensor --- circuit malfunction=== causes --- wiring-- ECT sensor
bump the cat converter with the heel of your hand and if it rattles replace the cat converter
if the cat converter is solid , replace the ECT

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Evap and cat converter monitor not showing ready when trying to smog 2001 daewoo nubira

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My check engine light is on and has a 421 error code? What does this mean?

OBD Code P0421refers to
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.
A code P0421 may mean that one or more of the following has happened: The catalytic converter is no longer functioning properly An oxygen sensor is not reading (functioning) properly A sparkplug is fouled up

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O2 sensors keep failing and a evap leak code i put new gas cap did not cgehan

Are you sure it's 02 sensors? Just because code says 02 sensors doesn't necessarily mean they're bad. Bad 02 sensor code can also indicate bad cat. converter. If 02 sensors read exact same reading before and after converter they will trigger OBC to "sensor fault" - they should be reading 2 different readings. (Pre CAT/POST cat) I'd suggest replacing cat converter before replacing sensors.

Mar 14, 2011 | 1999 Toyota Camry Solara

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I have a 2004 mitsubishi eclipse with the cat converter bad how long can i run with it with a bad converter will it ruin my engine anytime that part is too expensive $1000. what can i do

The Catalytic converter is used to reduce the toxicity of emission. I'm pretty sure it will not harm your engine if it is bad, but it will harm the environment. It could possibly also affect performance. Are you sure it is bad? does it make a very loud muffled sound out of the ordinary? It is a long shot but you can try changing the o2 sensor. The o2 sensor is a sensor that measures the pollution and oxygen going through your converter. If it doesn't meet the requirements it will most likely trip the engine light or cause problems as well. If you really have to replace it you can try ebaying the parts needed and then call around and see who can install it.

Mar 01, 2011 | 2004 Mitsubishi Eclipse

3 Answers

Po420 code monte carlo ls 2001

PO420 code is for catalyst system efficiency below threshold (bank 1) Usually it means that it is time for a new catalytic converter on bank number 1. Cylinder bank number 1 is always the bank with the number 1 spark plug in it.

Apr 20, 2010 | 2001 Chevrolet Monte Carlo

1 Answer

2000 E-350 V-10. P0174 with exhaust fix

Before I even finished reading this i knew you had a clogged cat. If you have fixed everything you mentioned i would lean towards a clogged cat. This is a large reason this code pops up.

To check this you could pull that cat out and drive around and see if the code comes back, make sure to stay away from the police though.


Mar 03, 2010 | 2000 Ford Econoline

2 Answers

Engine code p0420

The P0420 code is set when the oxygen sensor after the catalytic converter gives a reading the same or very close to the reading of the oxygen sensor(s) before the catalytic converter.

There are usually three possible causes...
The front oxygen sensor (before the cat) is giving an incorrect reading.
The rear oxygen sensor (after the cat) is giving an incorrect reading.
The catalytic converter is not working properly.

Since you recently replaced the cat, the logic points to the sensors, but it could be the cat again. Aftermarket converters are usually smaller than OEM and don't last as long.

For a more thorough description of the code and troubleshooting visit

Our Subaru encountered this issue several years ago under warranty. The first time the dealer replaced the front oxygen sensor. This was the cheapest repair and since it was an intermittent problem I am sure they hoped to delay the issue until the warranty was up. The second time they replaced the catalytic converter and we haven't had any more issues.

Jan 08, 2010 | 2000 Honda Civic

1 Answer

What does Code 2097 for a 2004 2.5 Subaru and how do I repair


Nov 27, 2009 | 2004 Subaru Impreza

1 Answer

01 eclipse

P0 421= Catalytic Converter(s) Below normal flow
P0 455= Evap system leak .. Gas Cap or Carbon cannister or possibly evap lines
P0 123=Drive cycle Incomplete ( no Biggy )
P0506= Idle air control motor..
Doesnt sound like that big of a deal. at our shop.., we'd replace the converter(s) Check the gas Cap for the evap code.. And replace the Idle control motor. The code P0123 should be cleared By ODB2 at that point and should be good to go.. Lemmie know.. Thanks

Mar 11, 2009 | 2001 Mitsubishi Eclipse

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