What California's smog check is and who has to get one

California's smog check is a vehicle emissions test required by the state to make sure your car doesn't pollute more than allowed. Most vehicles registered in California need one every two years, though some newer cars and certain vehicle types are exempt. The test measures what comes out of your tailpipe — specifically nitrogen oxides, particulate matter, and hydrocarbons — and compares those levels to state standards.

You'll need a smog check before you can register or renew your vehicle registration with the California Department of Motor Vehicles (DMV). If your registration expires and you haven't passed a smog check, you cannot legally renew it. The test costs money — typically between $30 and $70 depending on your vehicle type and the testing station — and you pay the station directly, not the state.

Key Takeaways

  • Most California vehicles need a smog check every two years before you can renew your registration with the DMV.
  • The test is performed at a Bureau of Automotive Repair (BAR) certified station, and you can find one using the official BAR station locator on the state website.
  • If your vehicle fails, you have 30 days to fix the problem and retest at no additional charge at the same station.
  • Vehicles from the current model year and some older vehicles are exempt, and you can check your vehicle's status on the BAR website before paying for a test.
  • You receive a smog certificate when ready after passing, which you bring to the DMV or provide when renewing online.

Which vehicles need a smog check and which don't

Not every vehicle in California requires a smog check. Vehicles from the current model year and the previous model year are exempt — so in 2024, that means 2023 and 2024 model year vehicles don't need one. Vehicles that are 1975 or older are also exempt. Electric vehicles and hydrogen fuel cell vehicles are permanently exempt because they produce no tailpipe emissions.

Motorcycles, trailers, and some commercial vehicles have different rules or are exempt entirely. The easiest way to know for certain is to enter your vehicle's information on the Bureau of Automotive Repair (BAR) website at bar.ca.gov. You can look up your specific vehicle by year, make, and model, and the site will tell you whether a smog check is required. This takes less than a minute and saves you a trip to a testing station if your vehicle is exempt.

Finding a certified smog check station

Smog checks must be performed at a station certified by the Bureau of Automotive Repair. You cannot get one at a regular mechanic's shop unless that shop is BAR certified. The BAR maintains a searchable list of certified stations on its website at bar.ca.gov — you can search by city, zip code, or station name.

When you call or visit a station, confirm that it's currently certified and ask about their hours and current wait times. Some stations are very busy during certain times of year, especially near registration renewal important date. You'll need to bring your vehicle keys and proof of vehicle ownership or registration, though requirements can vary slightly by station. Many stations can test your vehicle while you wait, though some may require an appointment.

What happens during the test and what the results mean

The smog check itself takes about 10 to 15 minutes. The technician will connect your vehicle to a machine that measures emissions from your tailpipe. For most vehicles, this is a straightforward plug-in process. The machine reads the levels of pollutants and compares them to the state's limits for your vehicle's year and type.

You'll receive one of three results: pass, fail, or conditional pass. A pass means your vehicle meets state standards and you can proceed to register or renew at the DMV. A conditional pass means your vehicle is close to the limit but still acceptable — you can register, but you may want to have your vehicle serviced to improve its emissions. A fail means your vehicle exceeds the state limit and you cannot register until you fix the problem and retest.

What to do if your vehicle fails the smog check

If your vehicle fails, you have 30 days from the test date to have the problem repaired and return to the same station for a retest at no charge. The station will give you a written report explaining what failed — usually something like a faulty oxygen sensor, a problem with the catalytic converter, or an issue with the fuel system. Take this report to a mechanic who can diagnose and repair the specific problem.

Some repairs are inexpensive — a few hundred dollars — while others can cost more. If your vehicle is very old or the repair cost is very high, you may want to get a second opinion from another mechanic before proceeding. Once the repair is done, return to the same testing station within 30 days for the retest. If you pass the retest, you receive a new smog certificate and can register your vehicle. If you fail again, you have another 30 days to repair and retest.

How to use your smog certificate to register your vehicle

Once you pass the smog check, the testing station will give you a smog certificate — usually a printed form with your vehicle information, the test date, and the passing result. You need this certificate to register or renew your registration with the California DMV. You can bring the physical certificate to a DMV office, mail it with your registration renewal, or upload it if you're renewing online through the DMV website.

If you renew online, the DMV website will ask you to enter the smog certificate number or upload an image of the certificate. Keep the original certificate until your registration is complete. The smog certificate is valid for 30 days from the test date, so plan your registration renewal accordingly. If your certificate expires before you register, you'll need to get another smog check.

Smog check exemptions and special situations

Beyond the standard exemptions for new vehicles and very old vehicles, California offers a few other situations where you might not need a smog check. If your vehicle is registered as a classic car or collector's item, it may be exempt. If you're registering a vehicle for the first time in California and it was previously registered out of state, the rules depend on the vehicle's age and when you moved to California.

If you have a vehicle with a gross vehicle weight rating (GVWR) over a certain threshold, it may fall under commercial vehicle rules and have different requirements. The BAR website has detailed information about these special cases. If your situation is unusual or you're unsure, you can contact the BAR directly at (916) 322-5859 or check the website before spending money on a test you might not need.

Frequently Asked Questions

Can I get a smog check before my registration expires?

Yes. You can get a smog check up to 90 days before your registration expires. This gives you time to fix any problems and still renew on time. The smog certificate is valid for 30 days, so if you test more than 30 days before your registration renewal date, you'll need to retest.

What if I move to a different county in California?

Your smog check is valid statewide, so you can get tested in any county and use that certificate to register in another county. The test itself doesn't change, but some counties have stricter emissions standards than others. If you move to a stricter county, your vehicle still only needs to meet the standard for its model year.

Do I need a smog check if I'm buying a used car from a private seller?

The seller is responsible for providing a smog certificate as part of the sale in California. If the vehicle doesn't have a current smog certificate, the seller must get one before transferring ownership to you. You cannot register the vehicle without it. Always confirm the smog certificate is included before completing the purchase.

What if the testing station says my vehicle can't be tested?

Some vehicles have problems that prevent testing — like a check engine light that won't clear, a broken speedometer, or a fuel cap that won't seal. The station will give you a written report explaining what needs to be fixed before testing can happen. Fix those issues first, then return for testing. This is different from failing the emissions test itself.

How long does it take to get my smog certificate after passing?

You receive your smog certificate when ready after passing the test, usually as a printed form before you leave the station. Some stations may offer digital copies via email. You can then take the certificate to the DMV right away or keep it until you're ready to renew your registration, as long as you use it within 30 days of the test date.