1997 Chevrolet C1500 Logo
Posted on Jun 30, 2009
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I keep getting code p0420. I replaced 2 cats, all 4 o2 sensors, plugs, wires, cap & rotor, cleaned air filter, sprayed maf sensor, new fuel injection spider, 2 mufflers. What is the problem?

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  • Marvin
    Marvin May 11, 2010

    P0420 is a Catalytic converter efficiency monitor code, why would you replace the O2 sensors?? the code indicated that the catalytic converter is worn out, did u do the pin point tests in the service manual?

  • Marvin
    Marvin May 11, 2010

    quit guessing and have the dealer fix this or use our live chat.

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averyless

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  • Posted on Oct 08, 2010
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P0420 code is usually a sign of s weak fuel pump, and needs to be replaced. Also if you replace the pump and still get that code, check your fuel lines back by the tank and make sure that they are not pinched or smashed. this will also give the same code due to restricted fuel pressure, on the ruturn or supply line........ Good Luck

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  • Posted on Jul 31, 2009
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Put some injector cleaner in your tank might have a clog ..K44 might help

  • arizonatruck Mar 12, 2012

    On half a tank of gasoline you might add 1 gallon of lacyer thinner which can be found in the paint section of most hardware stores or your local Wall Mart. $15.00 plus. I also disconnect the battery for 15 minutes to reset the computer code which is what the check engine light is trying to tell you that a sensor is detecting a issue. Lawyer thinner

  • arizonatruck Mar 12, 2012

    Lacquer thinner will clean out the fuel system and hopefully your catalic converter saving you the additional cost. I have now done this twice to my 2.4 liter nissan with two months inbetween applications

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  • Posted on Jul 01, 2009
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Are you running regular gas or not you should be running special unleaded fuel

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