Need help with CEL code

New Topics Forums General Discussion 2004 – 2009 Nissan Quest Need help with CEL code

This topic contains 2 replies, has 3 voices, and was last updated by  CanadaQ2005 7 years, 10 months ago.

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    check engine light is on on my 2005 Quest. Checked it at O’Reilly and their machine says:

    Catalyst System Efficiency Below Threshold (Bank 1)

    does anyone know what this means? What needs to be replaced?

    Thanks in advanced


    Ahh yes the this code again lol. I’ve got this code before. Catalytic Efficiency Running Below Threshold. Basically the Quest has 2 Catalytic Converters. Bank 1 and bank 2 tells which Cat is having the problem. Yours happens to be bank 1 which I do believe is the left side. Basically the Catalytic Converter is suppose to be running at 100% efficiency. If it starts running at 75% or below in efficiency it will trigger the code you got. It means the Cat is not running as efficient as it should be. In other words the inside of the Cat is burned out. This is a VERY VERY serious issue and I’d advise you get it fixed right away. The reason for this is since the inside of the Catalytic converter is burned out, those pieces inside break up inside and have no where to go but get sucked back up in the engine and will destroy it over a period of time. The code you got is either P0420 or P0430. You need to change that Bank 1 Cat right away.



    Is there any evidence to the theory of ‘sucking parts of cat back into the engine’?

    I would think that there is positive pressure in the cat from the exhaust gases, is there not?

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