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Smog Check Basics

Smog checks are designed to ensure the amount and type of pollutants your vehicle is emitting do not exceed maximum standards.

There are multiple components of any smog test, and your vehicle must pass all parts of the test to pass. The technician will also test other parts of your vehicle to make sure everything is running smoothly.

  1. Visual inspection of emissions control components and systems.

  2. Functional inspection of the vehicle’s check engine light, ignition timing, exhaust gas recirculation system, fuel evaporative system, and visible smoke.

  3. Functional inspection of the vehicle’s On-Board Diagnostic (OBD) system.

  4. Tailpipe emissions inspection (some vehicles are not subject to the tailpipe portion of the test).

After the inspection, you will receive a copy of the Vehicle Inspection Report (VIR), which contains the information stored on your vehicle’s computer. If your vehicle passes, the Referee will issue a certificate of compliance. If not, the Referee can point offer guidance about next steps.

Types of smog check stations

Smog Check Referee stations were created to perform more complicated smog inspections and handle special smog check circumstances. Most vehicles can be tested at regular stations. There are several different types of stations to choose from, depending on your situation:

  • STAR stations meet higher standards and are more closely monitored by the Bureau of Automotive Repair. Certain types of vehicles will be required by the DMV to be tested at a STAR station. 

  • Test-Only stations specialize in smog inspections and are not permitted to perform diagnostics or repairs. They were created to ensure fairness in California’s smog check program. Because these stations cannot make money off of repairs, consumers can feel secure knowing that there is no incentive to deliberately fail a vehicle. The DMV requires certain vehicles to be inspected at test-only facilities when the vehicle has a high chance of failing smog. The consumer is then free to take the vehicle to a repair station of their choice.

  • Test-and-Repair stations are authorized to perform smog inspections, diagnostics, and repairs. Consumers who believe their vehicle will need repairs should take their vehicle to a Test-and-Repair station for the initial inspection to simplify the process.

  • Repair-Only stations can diagnose and repair vehicles, but are not permitted to do any testing. This is a good option if you are planning on getting your test done at a different station later on. 


For the most up-to-date information on smog check process, laws and station types, visit the Bureau of Automotive Repair.

To find a smog check station near you, use the Bureau of Automotive Repair station locator.



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