98 Legacy OBD2 code P0420

Discussion in 'Subaru Legacy' started by Guest, Oct 9, 2004.

  1. Guest

    Guest Guest

    The car has 150,000 Km's (90,000 miles?). It has been flawless, until
    the MIL - P0420. Subaru dealer wanted to play "Replace parts til he's
    broke" I have changed the rear O2 sensor, now have a new catalytic
    converter. I do not wish to just keep throwing parts at it. I thought
    that a Subaru dealer should have the equipment to look at the ECM inputs
    and O2 outputs, etc...
    HELP... if anyone has experienced this or something like it, I would
    appreciate any help. Where do I go from here, BROKE ??
    Guest, Oct 9, 2004
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  2. Guest

    TG Guest

    What does that code mean? TG
    TG, Oct 9, 2004
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  3. Guest

    TG Guest

    OK, low catalyst efficiency. Usually replacing the exhaust manifold gaskets
    will cure this. I like to replace or at least chase the studs, you need an
    accurate torque reading here. Check for any other exhaust leaks upstream of
    the O2 sensors. TG
    TG, Oct 9, 2004
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