This document explains the diagnostic procedures that should be performed on vehicles to check emission levels of Carbon Monoxide (CO), Carbon Dioxide (CO2), Oxygen (O2), Hydrocarbons (HC), Nitric Oxides (NOx), and levels of Ammonia (NH3) and Water (H20) It also explains how each of the 5 pollutant gases are generated by the internal combustion engine. To locate the link, the user must go to CCAR greenlink topic menu of federal and state documents (in the green box at bottom of screen), click on the first drop down menu arrow, select �1700 � Emissions�, select �start search". Select number 1702.