Question about 2005 Cadillac CTS

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CTS CODE PO420

CHECK ENGINE LIGHT ON CODE READ PO420

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  • Anonymous Apr 08, 2009

    My 2003 CTSthe heater went out then the car overheayed onceandtheengine
    idle light came on, The check engine light used yocomeonperiodically. I
    had the car towed. @ people said heads andonesaidwater pump!!! I just
    had another mechanic he said he canotrecreatewhat happened and thinks
    it is just the oxygen sensor.Pleasehelp,

  • Anonymous Mar 14, 2014

    Po420 engine code on a 01 Chevy Blazer

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  • 1,010 Answers

Most of the time its the sensor that cause this,id try replacing the sensor on it,that usually fixes that code,but you have to get the code cleared off with a scanner ,and then re-scan it to make sure it doesn't come up again,good luck with it.

Posted on Jul 02, 2008

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Troubleshooting code PO420


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How much is it for a termistat change on cts plus check engine light and pollen air filter, what a fair price


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Check engine light on code po420


your catalytic converter has deteriorated inside the only fix is to replace the converter! you can drive with light on put your performance may suffer down the road latter on.

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The code PO420 came on for my 2000 Toyota Camray ......


Catalyst Effeciancy below threshold (Bank 1) is the code meaning. Check or replace the oxygen sensors. Some cars have 2 .One is on the front of the cat. the other is the on the back. Check the back sensor . Other possible causes are leaking or damaged exhaust manifold, bad coolant temp sensor.If toyota did not replace both . replace the one on the back of the Caty.

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