Who has to get a smog check and when

A smog check is an emissions test that measures how much pollution your vehicle produces. In California, you must pass a smog check before you can register or renew the registration of most vehicles. The requirement applies to cars, trucks, and motorcycles that are at least four model years old.

You need a smog check every two years when you renew your registration, unless your vehicle is brand new, is registered as a classic car, or runs on electricity. Some counties have different rules — a few allow smog checks every four years instead of two, so check your county's specific requirements before scheduling your test.

If you buy a used vehicle, you typically need a smog check before you can register it in your name, even if the previous owner just passed one. The test is tied to the registration process, not the vehicle's ownership history.

Key Takeaways

  • Most vehicles four model years old or older need a smog check every two years when you renew your registration.
  • You must pass the test before the Department of Motor Vehicles will issue or renew your registration.
  • The test costs between $30 and $70 depending on your vehicle type and the testing station you choose.
  • You can find a certified smog station through the Bureau of Automotive Repair website or by searching online for "smog check near me."
  • If your vehicle fails, you have 30 days to fix the problem and retest at no additional charge at the same station.

How to find a certified smog check station

Not every repair shop can perform a smog check — only stations certified by California's Bureau of Automotive Repair can conduct the test. You can search for certified stations on the Bureau of Automotive Repair website by entering your zip code, or you can call your local county environmental health department for a list.

When you call or visit a station, ask whether they test your specific vehicle type. Some stations specialize in certain vehicles — for example, a station may test passenger cars but not heavy trucks. Confirm the test fee ahead of time, as prices vary between stations.

You do not need an appointment at most stations, but calling ahead can save you a wait, especially during peak registration renewal periods. Bring your vehicle registration and a valid photo ID.

What happens during the smog check test

The test itself takes 10 to 30 minutes. A technician will connect your vehicle to a machine that measures emissions from your exhaust. For most vehicles, the test is non-intrusive — the machine plugs into your vehicle's diagnostic port, usually located under the steering wheel.

The technician will also perform a visual inspection, checking that your emission control equipment is in place and not obviously damaged. They will look at your catalytic converter, air filter, and other emissions-related parts.

Once the test is complete, you will receive a printed result when ready. If you pass, the station will send the results electronically to the Department of Motor Vehicles, and you can proceed with your registration renewal. If you fail, the station will give you a detailed report showing which emissions standards your vehicle did not meet.

What to do if your vehicle fails the smog check

If your vehicle fails, you have 30 days to repair the problem and return to the same station for a retest at no additional charge. The station's failure report will tell you which emissions systems need attention — for example, it might indicate a problem with your oxygen sensor or catalytic converter.

Take the failure report to a repair shop and have them diagnose and fix the issue. Some repair shops specialize in emissions repairs and may be more cost-effective than dealerships. Once repairs are complete, return to the original smog check station for the retest.

If you pass the retest, the station will send the passing result to the Department of Motor Vehicles. If you fail again, you can repeat the repair-and-retest cycle, but you will need to pay for additional tests after the first free retest.

Cost and timing for smog checks

A smog check typically costs between $30 and $70, depending on whether your vehicle has a standard engine or a diesel engine, and which testing station you use. Diesel vehicles usually cost more to test. Some stations may charge extra for vehicles that are particularly old or have high mileage.

The test itself takes 10 to 30 minutes, but you should plan for the possibility of a short wait, especially during busy registration renewal periods. Results are available when ready after the test.

Plan to schedule your smog check before your registration expires. If your registration has already expired, you cannot legally drive the vehicle until you renew it, which requires a passing smog check result. The Department of Motor Vehicles will not process your renewal without proof that your vehicle passed.

Vehicles that do not need a smog check

Electric vehicles and hydrogen fuel cell vehicles are exempt from smog checks because they produce zero emissions. Vehicles registered as classic cars, street rods, or custom vehicles may also be exempt, depending on how they are registered and your county's rules.

Vehicles that are fewer than four model years old do not need a smog check for their first registration. After that, they follow the standard two-year or four-year cycle depending on your county.

If you believe your vehicle should be exempt, contact your local Department of Motor Vehicles office or county environmental health department to confirm. Attempting to register a vehicle that requires a smog check without one will delay your registration.

What to bring and how to prepare

Bring your current vehicle registration and a valid photo ID to the smog check station. You do not need to bring any other documents unless the station requests them.

Before you go, make sure your vehicle is in reasonable running condition. If your check engine light is on, have the vehicle scanned for diagnostic trouble codes before the test — some stations will not test a vehicle with an active check engine light. If your vehicle has not been driven recently, take it for a short drive to warm up the engine before the test.

If you are buying a used vehicle and need a smog check as part of the purchase, ask the seller whether they will cover the cost. Some sellers include it in the sale price, while others expect the buyer to pay. This is negotiable and should be discussed before you finalize the purchase.

Frequently Asked Questions

Can I get a smog check if my vehicle has a check engine light on?

Most certified stations will not test a vehicle with an active check engine light. Have the vehicle scanned at a repair shop to identify the problem first. Once the issue is fixed or the code is cleared, you can return to the smog station for testing. Some stations may make exceptions, so call ahead to ask.

What if I move to a different county or state?

If you move within California, your smog check remains valid for registration renewal in your new county. If you move out of California, you will no longer need smog checks — they are a California requirement only. Contact your new state's Department of Motor Vehicles for their vehicle registration and emissions testing rules.

Do I need a smog check if I am renewing my registration online?

Yes. The Department of Motor Vehicles will not process your online renewal without proof of a passing smog check result. You must complete the test before you attempt to renew, whether you renew in person or online. The test results are sent electronically to the DMV, so the system will see that you have passed.

How long does a smog check result stay valid?

A passing smog check result is valid for 30 days. You must complete your registration renewal within that window. If your result expires before you renew, you will need to take another smog check test.

Can I get a smog check waiver if my vehicle fails?

California offers a smog check repair information program and a consumer information program for vehicles that fail and are expensive to repair. Contact your county's Bureau of Automotive Repair office to learn whether you may be may be able to access for a waiver or financial help with repairs. Requirements vary by county and vehicle age.