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Smog Check: Obtaining a California Smog Certificate

Why Do We Need Smog Checks?

The federal Clean Air Act (passed in 1970 and amended in 1990) mandates air pollution and air quality standards. More than 50 percent of air pollution is caused by motor vehicles. Yet only 10 to 15 percent of cars are responsible for that 50 percent.

Some areas of California exceed the federally mandated air pollution guidelines. California's Smog Check Program concentrates on "nonattainment" areas of the state—that is, areas where air pollution is above federal guidelines. These include the most populated areas of the state: Los Angeles, the San Francisco Bay Area, and Sacramento.

What Happens During a Smog Check?

Motor vehicles are inspected and, if needed, maintenance is performed to bring them into compliance. This is where the term I and M (inspection and maintenance) comes from

Vehicles are tested on an Emissions Inspection System (EIS). The system measures the chemicals in a vehicle's tail pipe emissions under various conditions, such as at different speeds and bearing different loads. The most common auto pollutants are carbon monoxide (CO), nitrous oxide (NO), and hydrocarbons (HCs). If the test shows any of these chemicals to be outside federal and state guidelines, the vehicle fails the smog check.

To verify that nothing has been removed or modified in the emission control system and that everything is in good working order, various other visual inspections and functional tests are performed. If the vehicle does not pass the visual or functional part of the smog check, the vehicle fails.

Who Needs a Smog Check?

All gas-powered and alternative-fuel automobiles and trucks (but not motorcycles) must be inspected every two years unless:

  • The vehicle is six years old or newer
  • The vehicle is a 1975 model or older
  • The vehicle is federally certified and under three years old with fewer than 7,500 miles

All gas-powered and alternative-fuel automobiles and trucks (but not motorcycles) also must be inspected when there is a change of ownership unless:

  • The vehicle is four years old or newer
  • The vehicle is a 1975 model or older
  • Ownership is being transferred within a family or business partnership

What Are My Choices if My Vehicle Fails?

If your vehicle fails and you were directed to a Test Only Smog Check station, you have several options. (The need to visit a Test Only station is indicated by a note on your DMV registration form.)

  • You may have the vehicle repaired at any Smog Check Test and Repair station at your expense, but the vehicle must be re-certified and pass at either a Test Only station or Gold Shield Smog Check Test and Repair station.
  • You may have the vehicle repaired and brought into compliance at your own expense at a licensed Gold Shield Smog Check Test and Repair station, regardless of the total cost of repairs.
  • You may have the vehicle repaired at a Gold Shield Smog Check Test and Repair station with assistance from the Consumer Assistance Program (CAP). CAP provides up to $500 worth of diagnostics and repair with either a $100 deductible or a $20 economic hardship deductible.
  • You may donate the vehicle for up to a $1,000 tax credit from the State of California.
  • If you have invested a minimum of $450 in diagnostics and repair (either out-of-pocket or through CAP), you can choose to pay the additional money needed to bring the vehicle into compliance or take the vehicle to a State of California Referee Center. You may receive up to a two-year exemption if the referee finds no evidence of tampering with the vehicle emission system.

Vehicles Not Directed to Test Only Stations

If your car fails a smog check and you were not initially directed to a Test Only Smog Check station, you have a different set of options.

  • If the vehicle fails as a "gross polluter" or because it was tampered with (such vehicles are referred to as "tampered"), there is no cost limit to repair the vehicle.
  • You may have the vehicle repaired and brought into compliance at your own expense at a licensed Gold Shield Smog Check Test and Repair station, regardless of cost.
  • You can attempt to repair the vehicle yourself (with no cost limit) and have a Test Only or Gold Shield Smog Check station run a re-certification smog check.
  • You may donate the vehicle for up to a $1,000 tax credit from the State of California.
  • You can apply for an economic hardship waiver, but there is no guarantee of approval of the waiver (as there is with Test Only Smog Check station–directed vehicles and CAP).

If the vehicle fails, but not as a gross polluter or tampered, you have a couple of options.

  • You may choose to repair the vehicle up to a $450 cost limit. If the vehicle still does not pass the smog check, you may elect to spend the additional money, or you can take the vehicle to a State of California Referee Center. Here, you may receive a waiver for up to two years, at which time the vehicle must be made fully smog check-compliant or surrendered to the state for up to a $1,000 tax credit.
  • If you repair the vehicle yourself, it can be retested at any licensed smog check station, but these repairs do not count toward the cost limit. Only licensed Smog Check Technicians at licensed Smog Check Test and Repair or Gold Shield Test and Repair Smog Check stations can do cost-limited repairs.

Parts Availability Repair Waiver

In any of the above failure cases, if the parts needed to bring the vehicle into compliance are not available, you may apply for a referee-approved parts availability waiver. Take the vehicle to a referee station and verify through documentation that the needed parts to repair the vehicle are not available. You can then receive up to a two-year waiver on repairing the vehicle, and the vehicle will be smog certified during the allotted time period.


Daniel Dillon has twenty-two years of experience as a licensed Smog Technician in California. He helped write test questions for the California Smog Technician Exam and has performed Consumer Assistance Program and gold shield diagnostic work for the state. He was also an instructor for SnapOn Tool Corporation.

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