California requires a smog test every two years for most vehicles, with some exceptions based on age and type

Your smog test schedule in California depends on when your vehicle was registered and what you drive. Most vehicles registered after 1975 need a test every two years. Vehicles registered before 1975 are exempt. If you own a vehicle registered in California, you'll receive a renewal notice from the Department of Motor Vehicles (DMV) that tells you whether a smog test is required before you can renew your registration.

The test itself checks your vehicle's emissions systems to may support they meet state standards. You cannot renew your registration without a passing test if one is required for your vehicle. The test costs between $30 and $70 depending on the test facility you choose, and results are sent electronically to the DMV within hours of completion.

Key Takeaways

  • Most California vehicles need a smog test every two years, timed to your vehicle registration renewal date.
  • Your DMV renewal notice will clearly state whether a test is required before you can renew.
  • Vehicles older than 1975 and some newer hybrids and electric vehicles are exempt from testing.
  • You must pass the test before the DMV will process your registration renewal, so plan ahead if your renewal is coming due.
  • Test results go directly to the DMV electronically, so you do not need to bring paperwork to the DMV yourself.

Which vehicles are exempt from smog testing

California exempts several categories of vehicles from smog testing. Any vehicle first registered before January 1, 1975 does not need a test. Diesel vehicles registered before 1998 are also exempt. Gasoline vehicles registered before 1976 are exempt regardless of current condition.

Some newer vehicles are exempt as well. Hybrid vehicles registered after 1999 do not require smog tests. All-electric vehicles are exempt. Vehicles that have been modified to run on alternative fuels may have different testing requirements depending on the fuel type and when the vehicle was registered.

If you are unsure whether your vehicle is exempt, check your DMV renewal notice. It will explicitly say "smog test required" or "smog test not required." You can also call your local DMV office or visit the California Air Resources Board (CARB) website to confirm your vehicle's status.

When your smog test is due

Your smog test is due before your vehicle registration expires. The DMV sends you a renewal notice 60 days before your registration expires. That notice tells you whether a test is required. If a test is required, you have until your registration expiration date to complete it and renew your registration.

Plan to take your test at least two weeks before your registration expires. Test facilities can be busy, and you want time to address any failures. If you fail the test, you will need to repair the vehicle and retest, which takes additional time. Some repair shops offer free or discounted retests if they performed the repairs.

If your registration expires before you complete a smog test and renew, you cannot legally drive the vehicle. Driving with an expired registration can result in a fine. If you know a test is coming due, schedule it as soon as you receive your renewal notice rather than waiting until the last week.

What happens if you fail the smog test

A failed smog test means your vehicle's emissions systems are not meeting California standards. The test report will identify which systems failed — typically the oxygen sensor, catalytic converter, or fuel system. You do not need to repair the vehicle when ready, but you cannot renew your registration until you pass.

Take the failed test report to a repair shop that specializes in emissions work. Many shops can diagnose the problem and provide a repair estimate. Some repairs are straightforward and inexpensive, like replacing a gas cap or fixing a loose hose. Others, like catalytic converter replacement, can cost several hundred dollars.

After repairs, you can retest at any smog test facility. Some facilities offer a retest fee that is lower than the initial test fee, typically $10 to $20. Once you pass, the results go to the DMV and you can complete your registration renewal. If you cannot afford repairs, some counties offer information programs for low-income vehicle owners, though availability varies by location.

Where to get a smog test

California has two types of smog test stations: STAR (Smog Test and Repair) stations and test-only stations. STAR stations can test your vehicle and perform repairs. Test-only stations perform the test but cannot do repairs. Both types are licensed by the Bureau of Automotive Repair (BAR).

You can find licensed test stations through the BAR website or by searching "smog test near me" online. Most stations accept walk-ins, though calling ahead to confirm hours is a good idea. Bring your vehicle registration and a valid ID. The test takes about 30 minutes. You do not need an appointment at most facilities.

Prices vary by location and station type. Test-only stations typically charge $30 to $50. STAR stations may charge $40 to $70 because they can also perform repairs. Some stations offer discounts for seniors or low-income drivers. Ask about pricing when you call or arrive.

How the smog test works

The smog test measures your vehicle's tailpipe emissions and checks the onboard diagnostic system. For most vehicles, the test takes about 10 to 15 minutes. The technician will connect a probe to your tailpipe and run your engine through a series of speeds to measure carbon monoxide, nitrogen oxides, and particulate matter.

The test also checks your vehicle's onboard diagnostic (OBD) system, which monitors emissions equipment. If the check engine light is on, the test will likely fail because the OBD system has detected a problem. Even if the light is off, the technician reads the diagnostic codes to may support no emissions-related issues are stored in the system.

Diesel vehicles and vehicles over 30 years old use different testing procedures. Diesel tests measure particulate matter and opacity. Very old vehicles may use a visual inspection instead of electronic testing. Your test facility will use the correct procedure for your vehicle based on its year and fuel type.

Preparing your vehicle for a smog test

Before you schedule a test, make sure your vehicle is in reasonable working condition. If the check engine light is on, have the vehicle scanned for diagnostic codes before testing. Many auto parts stores will scan for free. Address any emissions-related codes before you go to the test station.

Make sure your gas cap is tight and in good condition. A loose or damaged gas cap is a common test failure. Check that your tires are properly inflated and your engine oil is at the correct level. These basic maintenance items can prevent test failures.

If your vehicle has been sitting unused for a while, drive it for at least 20 minutes before testing to warm up the engine and clear any temporary fault codes. Avoid testing when ready after a long highway drive or when the engine is very hot. A vehicle at normal operating temperature performs best on the test.

Frequently Asked Questions

Can I renew my registration without a smog test if I just moved to California?

If you recently moved to California and registered your vehicle here for the first time, you may need a smog test before your first renewal. Check your DMV renewal notice. Vehicles newly registered in California follow the same two-year testing schedule as vehicles registered here longer.

What if I fail the smog test twice?

You can retest as many times as needed until you pass. There is no limit on the number of attempts. However, if you fail twice, you may want to take your vehicle to a certified repair shop rather than retesting on your own, because repeated failures suggest a more serious emissions problem.

Do I need a smog test if I am selling my vehicle?

California does not require a smog test as a condition of sale. However, the buyer may request one as part of their inspection. If you are buying a used vehicle, you can request a smog test before purchase to verify the vehicle will pass when you register it.

How long does a smog test result stay valid?

A passing smog test result is valid for 30 days. You must renew your registration within that 30-day window. If your registration renewal is delayed beyond 30 days, you will need a new test. Plan your registration renewal to complete within the 30-day window after testing.

Can I get a smog test waiver if my vehicle is too old to repair?

California offers a referee smog test for vehicles that fail and the owner cannot afford repairs. A referee station can issue a one-time waiver allowing registration renewal. You must meet income requirements and the vehicle must have failed a regular test first. Contact your local BAR referee station for details on the waiver process.