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Mk7.5 ecoboost P0420

jlawes20389
jlawes20389
in Ford Fiesta Club

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Hi all,

Looking to help a friend with her car which has just thrown a light with code P0420, catalyst below threshold.

It's recently passed an MOT and no issues on emissions, would the post cat sensor be a good place to start? Any tests with forscan I can do to check the sensor?

  • Quote


    46 minutes ago, jlawes20389 said:

    Hi all,

    Looking to help a friend with her car which has just thrown a light with code P0420, catalyst below threshold.

    It's recently passed an MOT and no issues on emissions, would the post cat sensor be a good place to start? Any tests with forscan I can do to check the sensor?

    Have a look in Mode 6. The figures might be double Dutch but both O2 sensors should be monitored as well as the Catalyst Oxygen storage capacity and individual cylinder misfire counts.

    If the O2 sensors are behaving themselves and the Fuel Trim is ok then the Cat might be passed its best.  

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    • Like 1
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    Perfect thank you. Gives me a place to start!

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