Experimental Study on Effects of OBD II Diagnostics on of Emissions for Light Vehicles

In view of various types of test vehicles (including American Standard vehicles and China 5 Standard vehicles), tests were carried out in accordance to requirements of American OBD II and China 5 OBD standards. Our measured results indicate that some emission pollutants may rise by about 10 times while the catalytic converter or oxygen sensor is failure or any misfire occurs for a China 5 Standard vehicle; and intensified monitoring requirements shall necessarily continue; on the other hand, NMHC, CO and NOx emission pollutants may grow by 100–900% for the engine cooling system, EGR, fuel system and VVT, respectively due to there being unique diagnostics cold start emission reduction strategies for OBD II; thus, the specific diagnosis requirements shall be necessarily introduced into Chinese OBD standards.