California smog tests are required every two years for most vehicles, with some exceptions based on age and type
In California, you need a smog test every two years if your vehicle is registered in the state. The test must happen within 90 days before your registration renewal date. If your vehicle is newer than six model years old, you do not need a smog test at all — California exempts new vehicles from the requirement. Vehicles that are 16 model years old or older also have different rules depending on whether they run on gasoline or diesel.
The exact timing depends on when your registration expires, not on the calendar. If your registration renews in June, your smog test must be completed between March and June of that year. You can take the test earlier if you want, but it will not be valid if you take it more than 90 days before your renewal date.
Key Takeaways
- Most California vehicles need a smog test every two years, timed to your registration renewal date.
- Vehicles six model years old or newer do not require a smog test, and vehicles 16 model years old or older may have different requirements.
- Your smog test must be completed within 90 days before your registration expires, or your renewal will be delayed.
- You can find your registration renewal date on your registration card or by checking the California Department of Motor Vehicles website.
When your vehicle does not need a smog test
New vehicles are exempt from smog testing for their first six model years. This means a 2024 model year vehicle registered in California will not need a test until 2030 at the earliest. The exemption is based on the model year, not the purchase date, so a 2023 model year car bought in 2024 would still be exempt until 2029.
Diesel vehicles 16 model years old or older do not need a smog test. Gasoline vehicles 16 model years old or older still need testing every two years. If you own a diesel truck or car and it is old enough, you can skip the test, but you will need to know your vehicle's model year to confirm.
Electric vehicles and hydrogen fuel cell vehicles are also exempt from smog testing. If your vehicle runs entirely on electricity or hydrogen, you do not need a smog test at any point during registration.
How to find your smog test due date
Your registration renewal date appears on your vehicle registration card, which you should have received from the California Department of Motor Vehicles. The card shows the month and year your registration expires. Count back 90 days from that date to find the earliest date you can take your smog test.
You can also check your renewal date online through the California DMV website by entering your license plate number. The DMV website will show you your exact expiration date and whether your vehicle needs a smog test. If you have lost your registration card, the online lookup is the fastest way to confirm your due date.
If your registration has already expired, you cannot legally drive the vehicle until you renew it. A smog test taken after your registration expires will not count toward renewal, so take the test before your expiration date passes.
What happens if you miss your smog test important date
If your registration expires before you complete a smog test, the California DMV will not process your renewal until you submit a passing test result. Your vehicle registration becomes invalid on the expiration date, and driving with an expired registration can result in a traffic citation.
You can still take a smog test after your registration expires, and the test will be valid for renewal purposes. However, you cannot legally drive the vehicle on public roads while your registration is expired. If you need to drive to the smog station, you risk a ticket for an expired registration.
Some smog stations offer appointment scheduling, which can help you plan ahead and avoid this situation. Booking an appointment a few weeks before your renewal date ensures you have a confirmed time slot and can complete the test well before your important date.
Different rules for commercial and fleet vehicles
Commercial vehicles registered in California may have different smog test schedules depending on their weight and use. Heavy-duty trucks and buses sometimes follow different testing cycles than passenger vehicles. If you own a commercial vehicle, check the California Air Resources Board website or contact your local smog station to confirm your specific testing requirements.
Fleet vehicles operated by businesses may also have different rules. Some fleets are subject to the California Heavy-Duty On-Road Diesel Vehicle Inspection Program, which has its own testing schedule separate from standard smog tests. If you manage a fleet, the California Air Resources Board can provide details about your obligations.
Where to get a smog test in California
Smog tests must be performed at a California-certified smog station. These stations are licensed by the California Bureau of Automotive Repair and display a visible smog station license. You can find certified stations near you through the California Bureau of Automotive Repair website by entering your zip code.
Independent smog stations, dealerships, and some repair shops all perform smog tests. Prices vary by location but typically range from $30 to $70 for a basic test. Some stations charge extra for vehicles that fail the initial test and need retesting after repairs.
When you arrive at a smog station, bring your vehicle registration card and a valid photo ID. The test itself takes 15 to 30 minutes. Once you pass, the station will submit your results electronically to the California DMV, and you can proceed with your registration renewal.
What to do if your vehicle fails the smog test
If your vehicle fails the smog test, you have 30 days to make repairs and retest at no additional charge at the same station. The station will provide a written report explaining which emissions standards your vehicle did not meet. Common reasons for failure include a faulty oxygen sensor, a loose gas cap, or a malfunctioning catalytic converter.
You do not have to use the same repair shop as the smog station. You can take the failure report to any mechanic and have them diagnose and fix the problem. Once repairs are complete, return to the smog station for a retest. If you pass the retest within 30 days, the station will submit your passing result to the DMV.
If you cannot afford repairs, some California counties offer repair information programs for low-income vehicle owners. Contact your county air quality management district to ask about repair grants or loans that might help you get your vehicle back into compliance.
Frequently Asked Questions
Can I take my smog test more than 90 days early?
No. A smog test taken more than 90 days before your registration renewal date will not be valid for renewal. You can take the test anytime within the 90-day window before your expiration date, but not before that window opens.
Do I need a smog test if I just bought a used car in California?
It depends on the model year. If the car is six model years old or newer, it does not need a smog test for its first registration in California. If it is older than six model years, you will need a smog test before you can complete the registration transfer.
What if I move out of California — do I still need a smog test?
No. Once you change your vehicle registration to another state, California smog test requirements no longer explore. You will need to follow the emissions testing rules of your new state instead.
Can I renew my registration without a smog test if my vehicle is exempt?
Yes. If your vehicle is exempt from smog testing — because it is newer than six model years, is a diesel vehicle 16 years or older, or is electric — you can renew your registration without submitting a smog test result. The DMV will process your renewal normally.
How long does a smog test result stay valid?
A passing smog test result is valid for 30 days from the test date. If you do not renew your registration within 30 days of passing, you will need to take another test. Plan to take your test close to your renewal date to avoid having to retest.