California's Smog Check is a vehicle emissions test required in most counties
Smog Check is California's vehicle emissions inspection program. Every two years (or annually for vehicles older than 1975), you must have your vehicle tested at a licensed smog station to prove it meets state air quality standards. The test measures what comes out of your tailpipe — carbon monoxide, nitrogen oxides, and particulate matter — and compares those levels against limits set by the California Air Resources Board.
Not all California counties require Smog Check. The state divides counties into two categories: those with air quality problems (mostly in the Central Valley and South Coast) where testing is mandatory, and those with cleaner air where it is not. You can find out whether your county requires it by checking your vehicle registration notice or the California Department of Consumer Affairs website.
The test itself takes about 10 to 15 minutes and costs between $30 and $50 at most stations. If your vehicle passes, the station sends the results electronically to the Department of Motor Vehicles, and you can renew your registration. If it fails, you have 30 days to repair it and retest at no additional charge.
Key Takeaways
- Smog Check is required every two years in high-pollution California counties, and you must pass before you can renew your vehicle registration.
- The test measures tailpipe emissions and takes about 10 to 15 minutes at a licensed smog station, costing $30 to $50.
- If your vehicle fails, you have 30 days to repair it and retest for free at the same station.
- Vehicles registered out of state, motorcycles, and vehicles under 6,000 pounds with a model year of 1975 or newer are generally exempt from testing.
Which vehicles need a Smog Check and when
Your vehicle needs Smog Check if you live in a county that requires it and your vehicle meets the age and weight thresholds. Generally, any vehicle registered in California with a model year of 1975 or newer and weighing 6,000 pounds or less must be tested. Vehicles older than 1975 are tested annually instead of every two years.
You do not need a Smog Check if your vehicle is registered out of state, if it is a motorcycle, if it is a diesel vehicle registered before 1998, or if it is a new vehicle in its first four model years. Electric vehicles and plug-in hybrids are also exempt. Check your registration renewal notice — it will say whether a test is required before you can renew.
The test is due by the expiration date on your registration. If you let your registration expire without passing Smog Check, you cannot legally drive the vehicle, and you may face fines when you renew.
How to find a licensed smog station and what to bring
Licensed smog stations are independent repair shops, dealerships, and chain service centers that have been certified by the California Department of Consumer Affairs. You can search for stations near you on the state's smog station locator website, which lists addresses, phone numbers, and hours. Not all repair shops are licensed to perform Smog Check, so verify the station's license before you go.
Bring your vehicle registration and a valid photo ID. The station will need your vehicle identification number (VIN), which is on your registration and on the dashboard. Some stations may ask for your keys so they can move the vehicle into the testing bay, but you do not need to leave the vehicle with them — the test is quick.
Call ahead if you want to confirm hours or ask about wait times. Many stations accept walk-ins, but some require appointments, especially during peak renewal periods.
What happens if your vehicle fails the test
If your vehicle fails Smog Check, the station will give you a printed report showing which emissions exceeded the limits. You then have 30 days to repair the vehicle and return to the same station for a free retest. You do not pay for the retest — the station is required to offer it at no charge.
Common reasons for failure include a faulty oxygen sensor, a loose or missing gas cap, a failing catalytic converter, or an engine light that is on. Many of these repairs are inexpensive, but some — like catalytic converter replacement — can cost several hundred dollars. If repairs are very expensive, you may be able to use the Smog Check information Program, which provides rebates or repair information in some counties for low-income vehicle owners.
If you cannot afford repairs or if your vehicle repeatedly fails, you may be may be able to access for a vehicle replacement or repair program through your county's air quality management district. These programs vary by location, so contact your local air quality agency to ask what is available.
Smog Check results and registration renewal
Once your vehicle passes, the smog station sends the test results directly to the California Department of Motor Vehicles electronically. You do not need to bring a paper certificate to the DMV — the results are in the system. You can then renew your vehicle registration online, by mail, or in person at a DMV office.
The results are valid for 30 days from the test date. If you do not renew your registration within that window, you will need to retest. Plan to get your Smog Check done within a few weeks of your registration expiration date to avoid this.
If you move out of state or to a California county that does not require Smog Check, you will not need to test again. However, if you move to a county that does require it, you will need to pass a test before you can register your vehicle there.
Smog Check for vehicles that fail multiple times
If your vehicle fails the initial test and then fails again after repairs, you enter a different process. After two consecutive failures, you may be able to request a referee inspection — a test performed by a state referee at a referee station. A referee can review whether the station's test was accurate and may allow you to pass under different standards if your vehicle is an older model or if the repairs you made were substantial.
To request a referee inspection, contact your local air quality management district or visit a referee station directly. You will need to bring your vehicle, the failed test reports, and proof of repairs. There is a fee for the referee test, usually $50 to $100, but it gives you another chance if you believe the initial test was wrong or if your repairs were not enough.
If your vehicle continues to fail, you may be may be able to access for the Smog Check information Program or a vehicle retirement program, depending on your county and income level. These programs can help pay for repairs or provide a rebate toward a newer vehicle.
Frequently Asked Questions
Can I get a Smog Check extension if my registration is about to expire?
No, the California DMV does not grant extensions for Smog Check. However, you can renew your registration online or by mail even if the test is not yet done — just do not drive the vehicle until it passes. If you fail and need repairs, the 30-day retest window gives you time to fix the vehicle.
What if I buy a used car and it fails Smog Check right after purchase?
The seller is responsible for providing a vehicle that passes Smog Check at the time of sale in California. If it fails when ready after, you may have a claim against the seller under California's used car lemon law. Contact the California Department of Consumer Affairs or a consumer protection attorney for guidance on your specific situation.
Do I need Smog Check if I only drive my vehicle occasionally?
Yes, if your vehicle is registered in a county that requires it, you must pass Smog Check before you can renew your registration, regardless of how often you drive. The test is based on registration status, not mileage or usage.
What if the smog station loses my test results?
The station is required to submit results electronically to the DMV within one business day. If results do not appear in the system within a few days, contact the station and ask them to resubmit. You can also call the DMV to confirm whether the results were received. If there is a problem, the station may need to retest you at no charge.
Can I transfer my Smog Check results if I sell my vehicle?
No, Smog Check results are tied to the vehicle and the registration. When you sell the vehicle, the new owner will need to pass their own Smog Check before they can register it in their name, unless the vehicle is brand new or exempt.