The California Smog Inspection consists of three types of tests depending upon where you live:
In order to pass California's emissions test, your automobile has to produce passing results in each of the 3 test sections.
The type of smog test required depends on the locale in which you live. Areas with the highest population densities require an Enhanced Test; the next level is a Basic test and finally the Change of Ownership area. Also, if a car's ownership ever changes, except between family members a smog check is required.
Enhanced Smog Test
Enhanced Smog Test - The Enhanced smog test requires your vehicle to be driven on a Dynamometer while the smog test machine collects emissions samples from the tailpipe. The Enhanced smog test has been shown to retrieve a more accurate sample of a vehicle's emissions output, than the Basic smog test. However as of 2013 new smog testing policies enacted under the STAR program have removed the requirement for a "tailpipe" test if your vehicle is later than year 2000 and you have a compatible ODBII computer.
The Basic Smog Test
The Basic Smog Test - This inspection requires vehicles be tested, just at idle and at 2500 RPM. The Basic smog test automobiles do not need to be driven on a Dynamometer. This test is required in counties in California with low smog pollution and usually have lower population densities. Smog stations in your local area will have the necessary computers to test your vehicle.
Change of Ownership Smog Test
Change of Ownership - In Change of Ownership areas of the state, smog checks are only needed when a vehicle is bought or sold, and when a used car is imported into the state of California. New cars imported into California by the automobile producer do not require smog checks. These cars are California licensed throughout production.
OBDII Smog Machine Link - The State of California requires all cars 1996 and up, to communicate directly with the smog machine throughout the smog test. This is attained via your car's OBDII data connecter. As part of the smog inspection process, the smog specialist will link a cable from the smog computer to your automobile's OBDII Data Link Plug. This cable will deliver "Check Engine" codes and "Readiness Flags" from the engine's computer system to the state's smog equipment.
Be advised that a smog test location cannot test your vehicle unless the readiness flags required for emissions testing are set. If you have recently had your vehicle serviced, in particular your electrical system or battery it is possible that the ODBII flags were reset. These flags will be set to the correct state after you drive your vehicle for a certain distance.
Emissions related failure codes returned by the ODBII computer will trigger your car to fail a smog inspection. The failure codes will be printed on the Vehicle Inspection Report (VIR) which will be given to you by the smog station.
Out-of-State Vehicles - There is a difference between California and Federal emissions equipped automobiles. And, for the most part CA has much stricter requirements. However, a used out-of-state vehicle which has only its federally required emission reducing parts, can pass the California smog test procedure and be legitimately registered in this state. California will nevertheless not enable new federally equipped cars into the state. New vehicle dealers who want to sell their items in California should import California emissions equipped cars exclusively. In other words, California will not limit customers from purchasing and bringing into the state a used car which is equipped with federal emissions parts , so long as the car was developed that method by the manufacturer.