A smog check, also known as an emissions test, is designed to make sure every car on the road is running as cleanly as possible. The check involves testing a vehicle’s engine emissions to determine how much pollution it’s exhausting into the air.
ABOUT SMOG CHECKS
The very first smog checks were performed in California in the 1960s. To this day, California is the only state with its own emissions standards, and they’re the toughest in the nation. The 31 other states that require smog checks can adopt either the Federal or California emissions standards.HOW OFTEN ARE SMOG CHECKS REQUIRED?
Most states, including California, require smog testing every two years, but not every car is required to have this done. Exemptions include:- Classic vehicles manufactured in 1975 or earlier
- New vehicles that are six years old or newer
- Diesel-powered vehicles from 1997 or earlier, or with a gross vehicle weight rating (GVWR) of 14,000 lbs or greater
- Natural gas-powered vehicles with a GVWR of 14,000 lbs or greater
- All-electric and electric hybrid vehicles
- Motorcycles
- Trailers
HOW DOES A SMOG CHECK WORK?
Your vehicle’s emissions are inspected visually and with special testing equipment that detects levels of carbon monoxide, carbon dioxide, hydrocarbons, nitrogen oxide, and emissions from evaporation. Three smog check methods are used in California:- OBD II test: The on-board diagnostics II test measures data provided by the car’s computerized diagnostic system. It’s used on any vehicle with an OBD II system, which includes all 1996 or 1997 and newer passenger cars and trucks.
- TSI test: The two-speed idle test measures exhaust through the tailpipe to calculate emissions when the car is idling. It’s most often used on older vehicles.
- ASM test: The acceleration simulation mode test measures exhaust while the car is being “driven” on a dynamometer. It’s usually reserved for very old vehicles.