Question about 2001 Hyundai Elantra

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PO420 code for 2003 Elantra

I have got a PO420 diagnostic code for my 2003 Hyundai Elantra, the sellsman said it was a Catalytic Convertor defective? Also gave a list of other possiabilities 2) Engine missfires or running problems (which this is not a problem) 3) Large Vacuum leak?? I have not heard any leakage and 4) Engine oil leakage into exhaust but i have not seen any smoking....So have any idea that it probley is the Catalystic Convertor...thanks Danny

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  • Anonymous Dec 16, 2008

    WILL IT PASS INSPECTION

  • single4_1999 Apr 10, 2009

    Still have the check engine light "on".. I replaced the CC and then a poor welding job but got it redone and the check Engine light came back on, it might be the Oxygen sensor, i am thinking about replacing it, waiting for the real SPRING weather..!! I will check back later!!

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Danny,

Catalytic Converter Failure is a common cause of a P0420 Code. 1.) I would give a few calls to some muffler shops and get a thorough exhaust inspection done. As a leaking/damaged Exhaust Manifold, Catalytic Converter, or exhaust pipe could be some of the culprits as well. If it were any of those other items your car would give you a different OBD Code. Item #2.) This is not common with a P0420 Code. With the P0420 code you should have no driveability issues. (not to say that you wouldnt in an extreme rarety) Item #3.) Again this would flag an entirely different code such as P0455 (Large Evap Emission Leak) Item#4.) Engine Oil would not even set a code. I hope this helps you out, and thank you for using FixYa!

Sincerely,

JC

Posted on Nov 19, 2008

  • raul mercado Apr 23, 2012

    I have a 2004 Hyundai Elantra and got a P0420 error code. A computer readout showed that it was the catalytic converter. I tried to fix the problem the usual way. First, I removed the negative battery terminal and allowed the computer to reset. That worked only a short while then the darn check engine light came back on. I then went to a friend of mine, who has a mechanic shop, and replaced the O2 sensor next to catalytic converter that worked for only a few hours. That solution worked for just a few hours and then the check engine light came back on. I live in NY where they have strict emissions test. The car was due for inspection. The warranty on the catalytic converter had expired. I was at a loss. That is until I got a devine stroke of genius.

    I went to the dealership and purchased an O2 sensor for the car, one straight from the manufacturer. It seems that my friend had installed a good O2 sensor but it was an aftermarket or generic piece. Once I got the new O2 sensor, I went to the auto grave yard and asked one of the guys if he could do me the favor and replace the O2 sensor. I paid him 30 dollars and he did the job which took about 10 minutes to complete. Shortly after that I dashed to Autozone, where they are doing free dashboard comuter analysis. What do you think happened next the fellow at Autozone told me that the error code was cleared.

    The check engine light has not come on since. A word of advice: Most of these components are electrical therefore if you are replacing them make sure that the negative battery terminal is disconnected. Spend the extra money and get specific parts made by the manufacturer. Shop around on line for out of state dealerships. My O2 sensor cost me $118. I have this feeling that if I would have gone to the dealership. I would have paid 10 times more. Not to say bad things about factory trained technicians but the work can be expensive. If after changing the O2 sensor after a few short hours you get the check engine light. Don't fret. Par the car, pop the hood and remove the negative battery terminal. But this time instead of removing it for 10 or 15 minutes. Leave the battery terminal disconnected for 5 to 6 hours. If you want to do it for a longer period of time, go ahead. Leave the battrery terminal disconnected overnight. This is the best computer reset. After you reconnect the battery terminal go for a 30 minute drive at 55 to 60 MPH. This should allow the computer to completely reset.

    Well, I am sorry that I was too wordy but I sincerely hope that this solution helps you or anyone else that may need it.

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I have a 2004 Hyundai Elantra and got a P0420 error code. A computer readout showed that it was the catalytic converter. I tried to fix the problem the usual way. First, I removed the negative battery terminal and allowed the computer to reset. That worked only a short while then the darn check engine light came back on. I then went to a friend of mine, who has a mechanic shop, and replaced the O2 sensor next to catalytic converter that worked for only a few hours. That solution worked for just a few hours and then the check engine light came back on. I live in NY where they have strict emissions test. The car was due for inspection. The warranty on the catalytic converter had expired. I was at a loss. That is until I got a devine stroke of genius.

I went to the dealership and purchased an O2 sensor for the car, one straight from the manufacturer. It seems that my friend had installed a good O2 sensor but it was an aftermarket or generic piece. Once I got the new O2 sensor, I went to the auto grave yard and asked one of the guys if he could do me the favor and replace the O2 sensor. I paid him 30 dollars and he did the job which took about 10 minutes to complete. Shortly after that I dashed to Autozone, where they are doing free dashboard comuter analysis. What do you think happened next the fellow at Autozone told me that the error code was cleared.

The check engine light has not come on since. A word of advice: Most of these components are electrical therefore if you are replacing them make sure that the negative battery terminal is disconnected. Spend the extra money and get specific parts made by the manufacturer. Shop around on line for out of state dealerships. My O2 sensor cost me $118. I have this feeling that if I would have gone to the dealership. I would have paid 10 times more. Not to say bad things about factory trained technicians but the work can be expensive. If after changing the O2 sensor after a few short hours you get the check engine light. Don't fret. Par the car, pop the hood and remove the negative battery terminal. But this time instead of removing it for 10 or 15 minutes. Leave the battery terminal disconnected for 5 to 6 hours. If you want to do it for a longer period of time, go ahead. Leave the battrery terminal disconnected overnight. This is the best computer reset. After you reconnect the battery terminal go for a 30 minute drive at 55 to 60 MPH. This should allow the computer to completely reset.

Well, I am sorry that I was too wordy but I sincerely hope that this solution helps you or anyone else that may need it.

Posted on Apr 23, 2012

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P0420 code is most of the time resolved by replacing the oxygen sensor (s) at a much lower cost than replacing a catalytic converter, if the later is really at fault.

Posted on Mar 06, 2012

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How did you make out. FYI, more P0420 info at http://p0420.com

Posted on Apr 10, 2009

  • Car Fixer Apr 11, 2009

    It probably will be the O2 sensor then. If you have access to an oscilliscope you can verify it's working right. Or you can just replace it. Also be sure there are no exhaust leaks because they can trigger more trouble codes.

  • raul mercado Apr 23, 2012

    I have a 2004 Hyundai Elantra and got a P0420 error code. A computer readout showed that it was the catalytic converter. I tried to fix the problem the usual way. First, I removed the negative battery terminal and allowed the computer to reset. That worked only a short while then the darn check engine light came back on. I then went to a friend of mine, who has a mechanic shop, and replaced the O2 sensor next to catalytic converter that worked for only a few hours. That solution worked for just a few hours and then the check engine light came back on. I live in NY where they have strict emissions test. The car was due for inspection. The warranty on the catalytic converter had expired. I was at a loss. That is until I got a devine stroke of genius.

    I went to the dealership and purchased an O2 sensor for the car, one straight from the manufacturer. It seems that my friend had installed a good O2 sensor but it was an aftermarket or generic piece. Once I got the new O2 sensor, I went to the auto grave yard and asked one of the guys if he could do me the favor and replace the O2 sensor. I paid him 30 dollars and he did the job which took about 10 minutes to complete. Shortly after that I dashed to Autozone, where they are doing free dashboard comuter analysis. What do you think happened next the fellow at Autozone told me that the error code was cleared.

    The check engine light has not come on since. A word of advice: Most of these components are electrical therefore if you are replacing them make sure that the negative battery terminal is disconnected. Spend the extra money and get specific parts made by the manufacturer. Shop around on line for out of state dealerships. My O2 sensor cost me $118. I have this feeling that if I would have gone to the dealership. I would have paid 10 times more. Not to say bad things about factory trained technicians but the work can be expensive. If after changing the O2 sensor after a few short hours you get the check engine light. Don't fret. Par the car, pop the hood and remove the negative battery terminal. But this time instead of removing it for 10 or 15 minutes. Leave the battery terminal disconnected for 5 to 6 hours. If you want to do it for a longer period of time, go ahead. Leave the battrery terminal disconnected overnight. This is the best computer reset. After you reconnect the battery terminal go for a 30 minute drive at 55 to 60 MPH. This should allow the computer to completely reset.

    Well, I am sorry that I was too wordy but I sincerely hope that this solution helps you or anyone else that may need it.

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Catalytic converter is clogged or out of medium.

Replace it.


ACTUAL DIAGNOSTIC:

Fault Code Definition
Code P0422 indicates that the Bank 1 Main Catalytic Converter's emissions efficiency has fallen below the minimum allowable limit. This threshold is tracked by a Catalyst Monitoring Oxygen Sensor located on or near the outlet of the Catalytic Converter.

Symptoms

* Check Engine Light will illuminate
* In many cases, no abnormal symptoms may be noticed

Common Problems That Trigger the P0422 Code

* Defective Catalytic Converter
* Engine misfires have damaged the Catalytic Converter
* Internal engine damage resulting in high oil consumption and/or a leaking Head gasket has damaged the Catalytic Converter

Common Misdiagnoses

* Oxygen Sensors are replaced when the real problem is a damaged Catalyst
* Catalyst is replaced when the real problem is internal engine damage, which is producing elevated emissions levels
* Catalyst is replaced when a misfiring engine is the real problem



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