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Need a little help. P0420

This is a discussion on Need a little help. P0420 within the General Help forums, part of the LSx Technical Help Section category; Originally Posted by Mustang=Breakfast Bad 02 sensors can give faulty codes like that... That is true. On my dads chevy ...

  1. #21
    lmpounded SandmanWs7's Avatar
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    Quote Originally Posted by Mustang=Breakfast View Post
    Bad 02 sensors can give faulty codes like that...
    That is true. On my dads chevy PU that was the problem.

  2. #22
    lmpounded SandmanWs7's Avatar
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    Causes:

    A code P0420 may mean that one or more of the following has happened:

    Leaded fuel was used where unleaded was called for
    An oxygen sensor is not reading (functioning) properly
    The engine coolant temperature sensor is not working properly
    Damaged or leaking exhaust manifold / catalytic converter / exhaust pipe
    Retarded spark timing
    The oxygen sensors in front and behind the converter are reporting too similar of readings

    Possible Solutions:

    Some suggested steps for troubleshooting a P0420 code include:

    Check for exhaust leaks at the manifold, pipes, catalytic converter. Repair as required.
    Use a scope to diagnose the oxygen sensor operation (Tip: The oxygen sensor in front of the catalytic converter normally has a fluctuating waveform. The waveform of the sensor behind the converter should be more steady).
    Inspect the downstream heated oxygen sensor (HO2), replace if necessary
    Replace the catalytic converter

  3. #23
    Veteran 0rion's Avatar
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    Quote Originally Posted by badbrad View Post
    I have 2002 Camaro B4C with 117,000Miles, had codes P0430 and p0420 and had dealer replace both CATs under warranty. Drove the car on the interstate 10 miles, back into stopped traffic, SES light came back on, code reads P0420.. What gives anthing else to kick this code on..
    the very first thing I would do is look under there to make sure the drivers side cat looks new. Might have told you they changed it when they didn't. If it looks new I would swap that rear sensor over to the passenger side and see if the code follows it before just buying a new sensor.

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