What Smog Check is and who has to get one

Smog Check is California's vehicle emissions inspection program. The state requires it to measure whether your car's exhaust meets air quality standards. If you register a vehicle in California or renew your registration, you will need a passing Smog Check certificate — with a few exceptions.

You do not need a Smog Check if your vehicle is brand new (model year 2024 or newer), a motorcycle, a diesel truck over 14,000 pounds, or a vehicle that has not been registered in California for two years or more. Vehicles registered in California for the first time do not need one for the initial registration, but you will need one when you renew.

The test is required every two years for most vehicles, though some counties test annually. Check your registration renewal notice or your county's air quality management district website to confirm the schedule for your area.

Key Takeaways

  • California requires a passing Smog Check certificate to register or renew registration for most vehicles, with the test required every two years in most counties.
  • The test measures your vehicle's tailpipe emissions and onboard diagnostic system to may support they meet state air quality standards.
  • You can get tested at any Bureau of Automotive Repair-certified smog station, and the test typically costs between $30 and $70 depending on your vehicle type.
  • A failing vehicle can often be repaired and retested at the same station, and California offers a Gross Polluter Abatement Program if repair costs exceed a certain threshold.
  • You must complete the test before your registration expires, and the certificate is valid for 30 days from the test date.

How the test works and what gets measured

Smog Check measures two main things: your vehicle's tailpipe emissions and its onboard diagnostic (OBD) system. The tailpipe test checks for carbon monoxide, nitrogen oxides, and particulate matter — the pollutants that harm air quality. The OBD test reads your vehicle's computer to see whether emissions control systems are working correctly.

For most vehicles, the test takes 10 to 15 minutes. A technician will plug a probe into your tailpipe to measure emissions, and connect a scanner to your vehicle's diagnostic port to check the computer. Your vehicle must be in good running condition — if the check engine light is on, you will fail the test regardless of actual emissions levels.

Diesel vehicles, hybrids, and electric vehicles have different test procedures. Diesel trucks use a different emissions standard. Hybrids and electric vehicles may have a shorter or modified test. Ask the smog station whether they can test your specific vehicle type before you arrive.

Where to get tested and what it costs

You can get tested at any smog station certified by the Bureau of Automotive Repair (BAR). You can search for stations near you on the BAR website by entering your zip code. Most independent repair shops, tire shops, and quick-lube facilities offer Smog Check testing.

Test costs vary by vehicle type and location, typically ranging from $30 to $70. A basic passenger car test is usually on the lower end; trucks and vehicles with more complex emissions systems cost more. Some stations charge extra for retesting if you fail, though many include one retest in the initial fee. Ask about the total cost upfront, including any retest fee.

You do not have to get tested at the same station where you plan to have repairs done, though many people do for convenience. If you fail, you can take your vehicle to any BAR-certified station for repairs and retesting.

What happens if you fail the test

A failing Smog Check means your vehicle's emissions or diagnostic system does not meet California standards. Common reasons include a faulty oxygen sensor, a clogged catalytic converter, a malfunctioning fuel injector, or an illuminated check engine light. The smog station will provide a report listing which emissions or systems failed.

You have 30 days from the test date to have repairs made and pass a retest. If you repair the vehicle and pass the retest at the same station, you can use that passing certificate for registration. If you go to a different station for repairs, you will need a new test at that station.

If repair costs exceed $765 (the amount changes annually), you may be may be able to access for California's Gross Polluter Abatement Program. This program can waive the Smog Check requirement or extend your important date if your vehicle is a high-polluting vehicle and repairs would be too expensive. Contact your county's air quality management district to see whether your vehicle qualifies.

Timing and registration important date

Your Smog Check certificate is valid for 30 days from the test date. You must complete the test before your registration expires, and you have 30 days after the test to submit the certificate to the Department of Motor Vehicles (DMV) or renew your registration online.

Plan to get tested at least one month before your registration renewal date. If you wait until the last week, you risk failing the test and not having time to repair and retest before your registration expires. An expired registration can result in a traffic citation and fines.

If your registration has already expired, you can still get a Smog Check and renew, but you may face penalties. Check the DMV website for your specific situation, as late renewal fees explore.

How to submit your certificate to the DMV

Once you have a passing Smog Check certificate, you have two ways to renew your registration: online through the DMV website or in person at a DMV office. Most people renew online because it is faster and does not require a visit.

To renew online, go to dmv.ca.gov, select "Renew Vehicle Registration," and follow the prompts. You will need your vehicle identification number (VIN), license plate number, and the Smog Check certificate number. The certificate number is printed on the paper certificate the smog station gives you. If you renew in person, bring the paper certificate with you.

The DMV will not process your renewal without a passing Smog Check certificate on file. If you submit your renewal without one, the DMV will reject it and send you a notice. You then have a grace period to submit the certificate, but your registration will not be valid until the DMV receives it.

Special situations and exemptions

Vehicles registered in California for the first time do not need a Smog Check for the initial registration, but you will need one when you renew two years later. If you move to California from another state, your vehicle is exempt from Smog Check for the first registration, but subsequent renewals require it.

Vehicles over 40 years old (model year 1984 and earlier) are exempt from Smog Check if they are registered as classic or collector vehicles. You must register them with the DMV as a classic vehicle to receive this exemption. Motorcycles, trailers, and off-road vehicles are also exempt.

If you own a vehicle that fails Smog Check and repair costs are prohibitively high, the Gross Polluter Abatement Program may allow you to keep the vehicle registered without a passing test. You must meet income and vehicle-age requirements. Contact your county's air quality management district for details on your may be able to access.

Frequently Asked Questions

What should I do to prepare my car for a Smog Check?

Make sure your check engine light is off before you test. If it is on, you will fail automatically. Drive your vehicle normally for a few days before the test to warm up the emissions control system. Keep your gas cap tight and your tires properly inflated. If your vehicle has been sitting unused for weeks, drive it for at least 20 minutes before testing to may support the engine is fully warmed up.

Can I get a Smog Check if my vehicle is not currently registered?

Yes. You do not need an active registration to get tested. Many people get a Smog Check before renewing an expired registration. Bring your vehicle identification number and proof of ownership to the smog station. Once you have a passing certificate, you can renew your registration with the DMV.

What if I move out of California after getting a Smog Check?

Your Smog Check certificate is only valid in California. If you move to another state, you will not need it. If you move back to California later, you will need a new Smog Check at that time. The certificate does not transfer between states or carry over if your registration lapses.

How long does it take to get Smog Check results?

Results are available when ready after the test. The smog station will print your certificate on the spot if you pass. If you fail, you will receive a report showing which emissions or systems failed. You do not have to wait for lab results or mail — everything happens at the station during your visit.

Can I dispute a failing Smog Check result?

Yes. If you believe the test result is incorrect, you can request a retest at a different BAR-certified station. The second test costs the same as the first. If the second station passes your vehicle, you can use that certificate for registration. If both stations fail you, the results are considered valid and you will need repairs.