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    2003 Nissan X Trail 2.0 Archived Message

    Posted by Bryan Smith on June 19, 2008, 6:32 pm

    Hi all,
    The above vehicle logged P0420 - Cat system efficiency below threshold, bank 1. I have checked the pre and post cat O2S and both appear to respond quickly to forced air leak or enrichment. Gases at 2500 rpm are CO 0.00%, HC's 6ppm, CO2 15.02% O2 0.04%, Lambda 1.002. I can't see anything wrong there. LFT is -3.1%. I have attached a couple of pics of the sensors and it would appear that the post cat sensor wont stay still. I am very loathe to condem the cat on this vehicle taking into account the gas readings. After I cleared the code it has not returned but it has not had much of a drive since then. the first two pics are 2500 rpm and the second two are at idle.

    2500 RPM
    2500 RPM
    Idle
    Idle

    Any suggestions or previous experience will be most appreciated.
    Many thanks, Bryan.

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