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P04020 Help!? Changed Everything Now

Alex12345
Alex12345
in Ford KA / StreetKA Club

Featured Replies

Hello new to this website but we have tried everything our garage has suggested and the fault code just keeps coming back.

We have a ford ka style 2006

and the fault code p0420 keeps appearing we've changed both lambda sensors and had a new new cat converter fitted,We had full service changed spark plugs oil etc. But still the problem keeps coming back the garage have run out of ideas and just say we should sell the car! We feel we've spent too much money on it just to give up now and are adamant it can be fixed. Any help would be greatly appreciated. Bare in mind I'm not particularly savvy with mechanical lingo so be as simple as you can. Thanks

  • Quote


    It would be worth checking the HOS fuse F30 (10A)

    You have to drop the fusebox to get to it and its the top right hand side fuse.

    This link should help you with access to the fuse http://www.fordownersclub.com/forums/topic/20365-streetka/

  • Quote

    im assuming you mean p0420 , not p04020, cat efficiency below threshhold.

    what you or your garage needs to do is check the outputs of both the sensors on ociliscope to see what wave forms are on both sensors.this will check if the new cat is working ok and both sensors are doing there job or not if thats the case

    no other dtcs?

  • Quote

    It would be worth checking the HOS fuse F30 (10A)

    You have to drop the fusebox to get to it and its the top right hand side fuse.

    This link should help you with access to the fuse http://www.fordownersclub.com/forums/topic/20365-streetka/

    would have thought blown fuse would trigger heater circuit dtcs on both sensors , but may not, worth checking

  • Quote
    • Author

    Yes sorry it must be the p0420 I did it from memory. I will try the fuse and ask at the garage when I neXT take it in. Thank you

  • Quote

    would have thought blown fuse would trigger heater circuit dtcs on both sensors , but may not, worth checking

    That's a very good point, was just a suggestion as everything seems to have been changed and as this fuse is hidden thought it could have been overlooked.

  • Quote
    • Author

    Just checked the fuse And it's fine thanks though was worth a try

  • Quote

    get the exhaust manifold checked

  • Quote
    • Author

    Thank you delboy I will the next time I take it in I think the Mrs has it booked it this week

  • Quote

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