Mac fault code
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This is a discussion on Mac fault code within the Engine Performance forums, part of the Tutorials & DIY category; I have a 04 wrx, it has no cat converter and a 3" exhaust, engine light came on, a Mac ...

  1. #1
    Registered User
    Join Date
    May 2008

    Mac fault code

    I have a 04 wrx, it has no cat converter and a 3" exhaust, engine light came on, a Mac code reader indicated fault code P0420, "cat efficiency below threshold, bank 1", it has been reset and keeps coming on, I've been told changing the sensor won't help. What next? Is there a "blocker?" or something else that can replace the sensor, so the check engine light stays off and the car performs like it should??

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  3. #2
    Super Moderator (Actually a SuperSpy) SD_GR's Avatar
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    Jul 2002
    CA, US
    I Support ClubWRX
    Search CEL PO420. Example:

    Need help!!!! with a MIL Eliminator

    There are two different solutions presented; I'd go for the cheapest.

    Also search EM or engine management.
    The world breaks everyone and afterward many are strong in the broken places. But those that will not break it kills. It kills the very good and the very gentle and the very brave impartially. If you are none of these you can be sure it will kill you too but there will be no special hurry. Ernest Hemingway, A Farewell to Arms, 1929
    WRX Info Links, Courtesy TheJ
    DISCLAIMER: Opinions expressed are the author's alone and are inherently worthless.

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