General "How To" How to Prevent a P0420 code with the Cat Removed

By MCS02 · Jan 7, 2020 ·
  1. MCS02
    If you are removing you catalytic converter on your Mini and want to prevent the post cat O2 sensor from causing a P0420 code this is a simple trick you can do. First I know you would only remove a cat on a track car that would never be used on the street and most of all, not in California where they would lock you away for life.

    What you need
    7/8 wrench
    Drill and 7/16 drill bit
    2 18mm Spark plug Non-Foulers (they come in a two pack)

    Go to your favorite parts store and buy two pack of Spark plug Non-Foulers I got mine at O'Reilly for $5.99


    Detroit Tuned has a O2 extender that does the same thing for $21.95, if you prefer

    Once you have your Non-Foulers you will need to drill one out so the O2 sensor can fit into it. A 7/16 drill bit is the size you will want to use.

    This picture shows how the O2 sensor fits after it has been drilled out.


    Now screw the two Non-Foulers together and than into the pipe.


    Then screw the O2 sensor into the non-foulers

    Yes I know that is a cat, this is just to show what is will look like when finished.

    If you have unplugged the O2 sensor plug it in and your done!

    They're are 3 other ways you can avoid getting a P0420 code. One is if you are getting a custom tune the tuner can code it out. The other way is to put a resistor inline with the O2 sensor. I have been told you can buy dummy O2 sensors but could not find them. This took about 15 minutes and was the whopping price of $5.99.

    Now go have fun!

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