How is the Smog Test Conducted? The California Enhanced smog check inspection is conducted in 3 distinct parts. First is a visual inspection to confirm that the emission control devices installed by the manufacturer are in place and properly connected. The second element is a functional test to see if the dash mounted "check engine or service engine soon" warning light is working properly, the gas cap will hold pressure and contain the fuel vapors within the void space at the top of the fuel tank and, for most pre 1996 model year vehicles, a pressure test of the EVAP system. Finally, the vehicle is placed on a special testing device called a dyne and the drive wheels are rotated and an emission reading is taken by a probe placed in the tailpipe of the vehicle. The information gathered is sent to an analyser and the results of the inspection are then sent to the Bureau of Automotive Repair Database and then on to the DMV. If passing, an electronic certificate is issued for that vehicle. If the vehicle fails to pass, the technician or another person will usually explain the cause of the failure to the owner and inform as to the various options available to remedy the failure.   Copyright 2009 AATC, Inc. All Rights Reserved