Skip to Content
chevron-left chevron-right chevron-up chevron-right chevron-left arrow-back star phone quote checkbox-checked search wrench info shield play connection mobile coin-dollar spoon-knife ticket pushpin location gift fire feed bubbles home heart calendar price-tag credit-card clock envelop facebook instagram twitter youtube pinterest yelp google reddit linkedin envelope bbb pinterest homeadvisor angies

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

If you’re not sure if you need an emissions test, check your vehicle registration renewal notice that comes in the mail. If it says, “Smog Certification Required,” you need to have the emissions tested before you can renew the registration. A smog check is also required if you’re selling the vehicle or switching to California license plates after moving to the state. Other provisions on a registration letter require STAR testing stations only.

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.

Where are Smog Checks Performed?

While some ordinary car repair shops can conduct smog checks, it’s best to visit a STAR Certified smog check station like All Tune and Lube in La Habra, CA. We perform smog tests and address your emission concerns all in one place.

Did your car fail its first smog check? Let us perform the repairs or maintenance required to get you compliant once again. We welcome all vehicle makes and models for emissions testing and repairs—you don’t even have to set an appointment! Simply bring in your car when it’s most convenient for you.

To speak to a knowledgeable mechanic about your remaining smog check questions, please call All Tune and Lube at 714-871-4144.

Leave a Reply

Your email address will not be published. Required fields are marked *