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

As a California resident, you are undoubtedly familiar with smog checks. After all, they are required biennially (every other year) on all vehicles that are more than eight model-years old. However, do you know how smog checks work? Here’s what to expect the next time you bring your car in for emissions testing.

Visual & Functional Inspections

First, a technician goes over the vehicle’s check engine light, ignition timing, exhaust gas recirculation system, fuel evaporative system, and gas cap. This portion of a smog check is intended to uncover any issues with the vehicle’s emission control components. If a fault in the system is causing the dashboard warning light to illuminate, you must have the malfunction repaired before passing a smog check.

A visual and functional inspection can also reveal if the emission system has been modified, disconnected, or otherwise tampered with. Altered vehicles can be configured to pass the tailpipe inspection but later changed to produce more emissions than the law permits.

OBD II Inspection

On-board diagnostic (OBD) tests have been used for years. OBD II, the second generation of on-board self-diagnostic equipment, is required on all 1996 or 1997-and-newer passenger vehicles operated in California. To check if your car is equipped with this feature, check for the words “OBD II” on the emission control information label on the underside of the hood.

In all areas of California, technicians are required to perform an OBD II inspection during a smog check. The purpose is to measure the data provided by your vehicle’s computerized diagnostics system, which reveals the functionality of virtually every component that could affect emission performance. The system stores information that can tell a smog check technician how cleanly the vehicle has been operating and whether any issues need to be addressed.

Tailpipe Emissions Inspection

For cars and trucks that aren’t equipped with OBD II, an old-school tailpipe test is used to measure levels of carbon monoxide, carbon dioxide, hydrocarbons, nitrogen oxide, and emissions from evaporation. Here are the two types of tests that may be used in place of an OBD II inspection:

  • 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 is typically reserved for very old vehicles. It incorporates a drive-on dynamometer that measures tailpipe emissions while the vehicle is “driving.”

After the Inspection

If your car passes the smog check, you’re all set for another two years. However, if your vehicle fails, you are required to seek the necessary repairs or maintenance to get your vehicle compliant once more.

Is it time for your next smog check? Are you looking for a mechanic to perform an emissions repair? Either way, All Tune and Lube has you covered. We are a certified STAR smog check mechanic in La Habra, CA. To ask questions or schedule an appointment, please call us at 714-871-4144!

Leave a Reply

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