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Po420 code monte carlo ls 2001 - 2001 Chevrolet Monte Carlo

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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.

Posted on Apr 20, 2010

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PO420 indicates a problem with the catalytic converter located in the exhaust. More specificly, three way catalyst efficiency low. Common causes for this fault are a failing or restricted converter or exhaust leaks. Catalytic conveters are generally covered by the factory warranty up to 100,000 miles.
In the event you meet this criteria, I would contact a local dealer in your area. (A history of engine misfire issues can also ruin the converter)
Good luck!

Posted on Apr 20, 2010

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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
http://www.obd-codes.com/p0420

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.

Posted on Apr 20, 2010

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SOURCE: what is this code po420 bank 1 in a che?vy monte

I could go on and on about Po420 code but it's easyer to tell you to go to www.po420.com and everything you want to know and then some is there. Let me know if this was helpfull..4 thumbs up !

Posted on Feb 24, 2010

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What is this code po420 bank 1 in a che?vy monte


I could go on and on about Po420 code but it's easyer to tell you to go to www.po420.com and everything you want to know and then some is there. Let me know if this was helpfull..4 thumbs up !

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