What Smog Check Is and Why California Requires It

Smog Check is California's vehicle emissions testing program. The state requires it to measure whether your car's exhaust meets air quality standards. If your vehicle fails, you cannot renew your registration until you repair it and pass a retest.

Los Angeles County is in a non-attainment area, meaning the region does not consistently meet federal air quality standards set by the Environmental Protection Agency. Because of this, the state uses Smog Check to identify and remove high-polluting vehicles from the road. The program has been running since 1984 and is administered by the California Bureau of Automotive Repair, a division of the Department of Consumer Affairs.

You do not pay the state directly for Smog Check. Instead, you pay a certified smog station — typically $30 to $70 for a basic test, depending on your vehicle type and the station's location. If your vehicle fails and needs repairs, you pay the repair shop separately.

Key Takeaways

  • Most vehicles registered in Los Angeles County need a smog test every two years; some newer cars are exempt for the first six years.
  • You must pass the test before you can renew your vehicle registration with the California Department of Motor Vehicles.
  • Smog stations are privately owned and certified by the Bureau of Automotive Repair; you choose which one to visit.
  • If your vehicle fails, you have 30 days to repair it and retest at no additional smog check fee, though repair costs vary widely.
  • Gross polluters — vehicles that emit far more than the standard — can be cited and required to repair when ready or face registration suspension.

Who Has to Get Tested and When

Most vehicles registered in California must pass Smog Check every two years. Los Angeles County residents follow this same schedule. Your registration renewal notice from the DMV will tell you whether your vehicle is due for testing.

Some vehicles are exempt. New cars are typically exempt for the first six years of registration. Vehicles that are 1975 or older are also exempt, as are some electric vehicles and motorcycles. Diesel vehicles over 14,000 pounds are tested under a separate program. If you are unsure whether your vehicle is exempt, the Bureau of Automotive Repair website has a lookup tool, or you can ask at any certified smog station.

You must complete the test before your registration expires. If you renew your registration without passing Smog Check, the DMV will flag your account, and you may face penalties or registration suspension.

How to Find a Smog Station and What to Bring

Smog stations are privately owned repair shops and service centers certified by the Bureau of Automotive Repair. You can find one near you by searching the Bureau's online station locator at bar.ca.gov, or by searching "smog check near me" in any map process. Prices vary, so calling ahead to compare is common.

Bring your vehicle registration and a valid photo ID. The technician will run your vehicle through a tailpipe emissions test (for older cars) or an onboard diagnostic test (for newer cars). The test takes 10 to 30 minutes. You do not need an appointment at most stations, though some accept them.

Your vehicle must be in running condition and have fuel in the tank. If your check engine light is on, the test will likely fail. Some stations can diagnose the problem, but diagnosis and repair are separate from the smog test itself.

What Happens If Your Vehicle Fails

If your vehicle fails, the smog station will give you a written report listing the emissions that exceeded the standard. You then have 30 days to repair the vehicle and return to any certified smog station for a retest. The retest itself costs the same as the initial test — you do not pay twice for the smog check portion.

Repair costs depend entirely on what is wrong. A failed oxygen sensor might cost $100 to $300 to replace. A failed catalytic converter can cost $500 to $2,500 or more. Some repair shops offer payment plans or financing. If repair costs exceed a certain threshold (the amount varies by vehicle age and model year), you may be able to request a gross polluter waiver from the Bureau of Automotive Repair, which temporarily suspends the repair requirement — but this is uncommon and has strict conditions.

If you do not repair and retest within 30 days, your registration will not renew, and you cannot legally drive the vehicle. You can request an extension if you have a documented reason, such as waiting for parts.

Gross Polluters and Repeat Failures

A gross polluter is a vehicle that emits pollution at levels far above the standard — typically three or more times the limit. The Bureau of Automotive Repair identifies these vehicles through Smog Check data and may send the owner a notice requiring when ready repair.

If you receive a gross polluter notice, you must repair the vehicle within a set timeframe (usually 30 days) and pass a retest. Failure to do so can result in registration suspension and fines. Some gross polluters are repeat failures — vehicles that have failed Smog Check multiple times. These face stricter enforcement.

If your vehicle fails Smog Check twice in a row, the Bureau may require you to use a referee station for your next test. A referee station is a Bureau-operated facility that conducts independent testing to verify whether the vehicle actually meets standards. Referee tests cost more (typically $70 to $100) but are used to resolve disputes or confirm repeated failures.

Your Rights and Options if You Disagree With a Result

If you believe a test result is wrong, you have options. You can request a retest at a different certified station — there is no penalty for retesting, and you pay the station's fee again. Many vehicle owners do this if they suspect a station made an error.

You can also request a referee test through the Bureau of Automotive Repair. A referee station will conduct an independent test of your vehicle's emissions. This costs more than a regular smog test but is binding and can overturn a previous failure if the vehicle actually meets standards. To request a referee test, contact the Bureau directly or ask a smog station for the process in your area.

If you believe a station charged you unfairly or conducted the test improperly, you can file a complaint with the Bureau of Automotive Repair. The Bureau investigates complaints about certified stations and can revoke a station's certification if it finds violations.

Smog Check and Vehicle Registration Renewal

Once your vehicle passes Smog Check, the result is sent electronically to the California DMV. You do not need to bring a paper certificate to the DMV — the agency sees the passing result in its system.

You can then renew your registration online through the DMV website, by mail, or in person at a DMV office. Registration renewal costs vary by vehicle type and county but are separate from the smog test fee. If you renew your registration before passing Smog Check, the DMV will reject the renewal and ask you to complete the test first.

Your smog test result is valid for 30 days. If you do not renew your registration within that window, you will need to retest when your registration comes due again.

Frequently Asked Questions

Do I need a smog check if I just bought a used car in California?

Not when ready. You have until your first registration renewal to pass Smog Check. However, if you are transferring the registration from the previous owner, you must pass the test before the DMV will complete the transfer. Check your registration notice or contact the DMV to confirm the important date for your specific vehicle.

What if my vehicle is registered out of state but I live in Los Angeles?

If you move to California and register your vehicle here, you must pass Smog Check before the DMV will issue a California registration. Out-of-state vehicles are not exempt. Some states have stricter emissions standards than others, so a vehicle that passed in another state may fail in California.

Can I get a smog check waiver if my car is old or rare?

Vehicles from 1975 and earlier are exempt from Smog Check. Some classic or collector vehicles may also be exempt if they are registered as such with the DMV. Check the Bureau of Automotive Repair's exemption list or ask the DMV whether your specific vehicle qualifies. If it does not, you must test it like any other vehicle.

What happens if I drive without passing smog check?

Driving with an expired registration is illegal and can result in a traffic citation and fine. If your registration has expired because you did not pass Smog Check, you cannot legally operate the vehicle on public roads. You must pass the test and renew your registration before driving again.

How long does it take to get smog check results?

Results are typically available when ready after the test at the station. The station sends the result electronically to the DMV within one business day. You can then renew your registration right away — you do not need to wait for mail or official paperwork.