Q: I can't pass smog because the NO ppm is just a little high. What are the problems? Can you help me please?

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Can't pass smog failed twice due to the NO ( ppm) being to high for average pass at 15mph max 350 measured 625 & 25 mph Max 527 measured 592 can you please tell me what's wrong?

My car has 218988 miles.
My car has an automatic transmission.

Hi there. When an engine burns fuel mixed with oxygen in the combustion chamber, carbon monoxide, unburned hydrocarbons, and oxides of nitrogen NOx. NOx is a generic term for the nitrogen oxides that are most relevant for air pollution, namely nitric oxide (NO) and nitrogen dioxide (NO2). An engine that runs on the hot side; or has what is referred to as a LEAN fuel mixture, produces excessive levels of NOx; which can produce an instant fail for most emissions tests. Lean engine conditions are typically caused by O2 sensors that are not correctly working or mass air flow sensor that is not working as well. The best way to diagnose this problem is to have a professional mechanic come to your location and complete a check engine light inspection, so they can determine if error codes exists in the ECU of your Nissan Quest that will indicate which component is faulty and needs to be replaced in order to improve your emissions.

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