P0420 fault code

Discussion in 'Ibiza Mk4' started by mark_eisner, Jan 20, 2011.

  1. mark_eisner

    mark_eisner Full Member

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    I've been getting a recurring DTC: P0420: Catalyst System; Bank 1: Efficiency Below Threshold

    No obvious symptoms but I think the economy is reduced (running rich?)

    It's on a 1.2 12V 2003 Ibiza

    I have replaced the pre-cat oxygen sensor but the code keeps coming back. The other things that the Ross-Tech wiki says are to check the catalyst and check the intake and exhaust systems. I'm assuming it means check for leaks. The exhaust system I can check easily but the intake system is a little more complex. Where are the places I should check and how do I check? I know there isn't a gapping hole in the throttle body so I assume it will be more subtle.

    :(
     
  2. We have had a couple of these and fixed them with a replacement air flow meter.
     
  3. mark_eisner

    mark_eisner Full Member

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    Thanks, will look into it!
     
  4. mark_eisner

    mark_eisner Full Member

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    I can't find any reference to the air flow meter (MAF) for the 1.2. I've looked on parts sites and in my haynes manual, the only reference is for diesels.

    Is the part you mean the joint intake pressure/temperature sensor. I think also MAP?
     
  5. Yes sorry just a terminology thing
     
  6. mark_eisner

    mark_eisner Full Member

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    Thought so, just inexperienced!
     
  7. mark_eisner

    mark_eisner Full Member

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    I've just replaced my MAP. The old one had oily deposits all around the probe, is this normal?
     
  8. canis_lupis

    canis_lupis Guest

    Yes it can do from recirculation from cam cover, did it fix the problem?
     
  9. mark_eisner

    mark_eisner Full Member

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    Not sure yet, am going for a drive in about 20 mins, the fault code usually only came on after the second motorway journey. It was fine on the first 70 then the code came back up the second time. Quite predictably actually.
     
  10. seremotors

    seremotors Dave the Parts Manager

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    Worth looking for green furry corrosion on the O2 sensor multiplug ;-)
     
  11. mark_eisner

    mark_eisner Full Member

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    The post-CAT O2 sensor? Does that just need a clean or sensor replacement?
     
  12. mark_eisner

    mark_eisner Full Member

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    Is there a way to check what is broken/has a bad connection with vag-com? Looking at the outputs etc to see if it's nonsense? I just don't know what readings are normal etc...
     

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