What California's smog test law requires

California requires a smog test every two years for most vehicles, and every year for vehicles model year 1975 and older. The test checks your vehicle's exhaust for nitrogen oxides, particulate matter, and other pollutants. You must pass before you can renew your vehicle registration, and you cannot register a vehicle in California without a current passing test on file.

The test itself takes about 10 to 15 minutes at a Bureau of Automotive Repair (BAR) certified smog station. A technician plugs a diagnostic machine into your vehicle's onboard computer and measures what comes out of the tailpipe. If your vehicle passes, the station sends the results electronically to the Department of Motor Vehicles (DMV). If it fails, you get a written report showing which pollutants exceeded the limit.

You do not need to bring any paperwork to the test itself, but you do need to know your vehicle identification number (VIN) and current mileage. The station will have your registration information on file once you provide your license plate number.

Key Takeaways

  • California requires a smog test every two years for most vehicles, with the test results sent directly to the DMV by the testing station.
  • Vehicles model year 1975 and older, diesel vehicles, and brand-new vehicles have different testing schedules or are exempt entirely.
  • A passing test costs between $30 and $50 at a BAR-certified station, and you can find certified stations through the Bureau of Automotive Repair website.
  • If your vehicle fails, you have 30 days to repair it and retest at no additional charge at the same station.
  • You cannot renew your registration without a passing smog test result, and the DMV will not process your renewal until the test is on file.

Which vehicles need a smog test in California

Most gasoline-powered passenger vehicles registered in California need a smog test every two years. This includes sedans, SUVs, pickup trucks, and vans. The test is due in the month your registration expires, and you must have a passing result before the DMV will renew your registration.

Diesel vehicles have a separate testing program and are tested every two years as well, but at a different standard. Vehicles model year 1975 and older are tested every year instead of every two years. Brand-new vehicles (current model year) are exempt for the first four years of registration.

Vehicles that are registered as non-operational, historic, or off-highway are exempt. Hybrid vehicles and electric vehicles are also exempt from smog testing. If you are unsure whether your vehicle needs a test, the DMV website allows you to check by entering your license plate number.

Where to get your smog test and what it costs

You must use a Bureau of Automotive Repair (BAR) certified smog station. These are independent repair shops, dealerships, and service centers that have passed state inspection and use approved testing equipment. You cannot get a smog test at a general auto parts store or a car wash.

The test costs between $30 and $50 at most stations, though prices vary by location and station. Some stations charge a small additional fee if your vehicle fails and you return for a retest, though California law allows one free retest within 30 days at the same station. You can find certified stations near you through the Bureau of Automotive Repair's online station locator at bar.ca.gov, or by searching "smog test near me" and verifying the station's BAR certification number.

You can schedule an appointment at most stations, though many also accept walk-ins. Bring your vehicle keys, your driver's license, and know your vehicle's current mileage. The test takes 10 to 15 minutes, and you will receive a printed receipt with your results on the spot.

What happens if your vehicle fails the smog test

If your vehicle fails, the station gives you a written report showing which pollutants exceeded the limit. You then have 30 days to repair the vehicle and return to the same station for a free retest. The station will hold your test record for 30 days to allow time for repairs.

Common reasons for failure include a faulty oxygen sensor, a malfunctioning catalytic converter, a loose gas cap, or an engine problem that triggers the check engine light. A mechanic can diagnose the specific issue using the failure report. Repairs can range from $50 for a gas cap replacement to several hundred dollars for a catalytic converter.

If you cannot afford repairs, some counties offer repair information programs through the California Bureau of Automotive Repair. You can also contact your local air quality management district to ask about repair rebates or low-income information. If you retest within 30 days and pass, the passing result is sent to the DMV and your registration can be renewed.

How to renew your registration after passing the smog test

Once your vehicle passes the smog test, the station sends the results electronically to the DMV within one business day. You do not need to do anything else — the DMV receives the test result automatically. You can then renew your registration through the DMV website, by mail, or in person at a DMV office.

When you renew online or by mail, the DMV checks whether a passing smog test is on file. If it is, your renewal processes normally. If no test result is found, the DMV will not complete your renewal and will send you a notice asking you to provide proof of a passing test.

If you are renewing in person at a DMV office, bring your current registration and a valid ID. The staff will verify that your smog test result is in the system before processing your renewal. Registration renewal fees vary by vehicle type and weight, and you can pay online, by mail, or at the office.

Smog test timing and registration renewal important date

Your smog test is due in the month your vehicle registration expires. For example, if your registration expires in June, you must have a passing smog test result on file by the end of June. You can take the test up to 60 days before your registration expires, so you can test as early as May.

If you miss the important date and your registration expires without a passing test, you cannot legally drive the vehicle. The DMV will not renew your registration until you provide a passing smog test result. If you are pulled over while driving an unregistered vehicle, you face a fine and potential vehicle impound.

If your registration has already expired, you can still get a smog test and renew your registration at any time. There is no penalty for renewing late, but you cannot legally operate the vehicle until the registration is current. Plan to test at least two weeks before your registration expires to allow time for repairs if needed.

Frequently Asked Questions

Can I get a smog test before my registration expires?

Yes. You can test up to 60 days before your registration expires. This gives you time to repair and retest if your vehicle fails. The test result is valid for the full two-year registration period once you pass.

What if I move out of California — do I still need a smog test?

No. Once you register your vehicle in another state, California's smog test requirement no longer applies. However, you must have a passing California smog test on file before the DMV will release your registration for out-of-state transfer.

Do I need a smog test if I buy a used car from a dealer?

The dealer must provide a passing smog test before you take ownership. However, once you register the vehicle in your name in California, you are responsible for future tests on the two-year schedule. Your first test will be due two years after the vehicle's registration date.

What if the smog station says my vehicle cannot be tested?

Some vehicles cannot be tested if the onboard diagnostic system is not working or if the vehicle is in unsafe condition. The station will provide a written explanation. You can take the vehicle to another BAR-certified station for a second opinion, or have a mechanic repair the issue and try again.

Can I test my vehicle in a different county than where it is registered?

Yes. You can test at any BAR-certified station in California, regardless of which county your vehicle is registered in. The test result is sent to the DMV statewide database and is valid for registration renewal anywhere in the state.