There are several reasons your Nissan Pickup Truck could be producing high NO. The most common is the defective EGR system. The EGR valve is responsible for re-circulating a small amount of exhaust gas back into the combustion chamber. This cools the chamber temperature by producing an inert gas along with the regular fuel mixture. Your Nissan Pickup truck produces Nitrous Oxides (NO) when engine temperature rises above 2500* F. Keeping the chamber cool reduces NOx emission.
For more reasons your Nissan Truck could be producing high NO follow this link.
