What California's Smog Check Law Requires

California requires most vehicles to pass a smog check every two years, though some newer cars and electric vehicles are exempt. The test measures your vehicle's emissions to may support it meets state air quality standards. You cannot renew your vehicle registration without a current smog check certificate, and you must show proof when you register or transfer ownership of a vehicle.

The smog check is not optional — it is a condition of legal registration in California. If your vehicle fails, you have options to repair it and retest, but you cannot legally drive on public roads without either passing the test or obtaining a waiver from the state.

Key Takeaways

  • Most California vehicles need a smog check every two years as a requirement for registration renewal.
  • Vehicles model year 1975 and older, and most vehicles model year 2000 and newer, are exempt from smog check requirements.
  • You must pass the smog check before you can renew your registration, and the certificate is valid for 30 days.
  • If your vehicle fails, you can repair it and retest at the same station, or seek a Gross Polluter Repair information Program waiver if repairs cost too much.

Which Vehicles Must Get a Smog Check

Your vehicle's model year determines whether you need a smog check. Vehicles model year 1975 and older do not require one. Most vehicles model year 2000 and newer are also exempt, though some 2000 model year vehicles may still need testing — your registration notice will tell you if yours does.

Vehicles model year 1976 through 1999 almost always require a smog check. Diesel vehicles have different rules: most diesel vehicles model year 1998 and newer are exempt, but older diesel vehicles may need testing. Electric vehicles and hydrogen fuel cell vehicles are exempt.

If you are unsure whether your vehicle needs a smog check, check your vehicle registration renewal notice — it will state whether a smog check is required. You can also contact the California Department of Consumer Affairs' Bureau of Automotive Repair or call your local smog check station.

When You Must Get Your Smog Check Done

You must obtain a smog check before you renew your vehicle registration. The smog check certificate is valid for 30 days from the test date, so plan your test timing to align with your registration renewal important date. If your registration expires on June 15, you can test anytime from May 16 onward and still have a valid certificate when you renew.

When you buy a used vehicle in California, you typically need a smog check within 90 days of purchase before you can transfer the title and register it in your name. Some counties have different rules for used vehicle transfers, so check with your local Department of Motor Vehicles office.

How the Smog Check Test Works

A smog check station uses equipment to measure your vehicle's exhaust emissions. For most vehicles, the test takes 10 to 15 minutes and involves connecting a probe to your vehicle's tailpipe while the engine runs at different speeds. The equipment measures levels of nitrogen oxides, carbon monoxide, and other pollutants.

The test is performed by a technician certified by the California Bureau of Automotive Repair. You do not need to do anything special to prepare your vehicle — just bring it in with a full fuel tank and a clean windshield so the technician can see the odometer reading.

The cost of a smog check varies by station but typically ranges from $30 to $70. Some stations charge extra if your vehicle fails and you want to retest when ready. Ask the station for their pricing before you start the test.

What Happens If Your Vehicle Fails

If your vehicle fails the smog check, you have 30 days to repair it and retest at the same station. The station will give you a detailed report showing which emissions exceeded the limits. You can take this report to a mechanic to understand what repairs are needed.

If repairs cost more than a certain amount — currently $500 for most vehicles, though this threshold changes yearly — you may be able to obtain a Gross Polluter Repair information Program waiver. This waiver allows you to register your vehicle without passing the smog check. To may have access to, your vehicle must have failed the test, and the repair estimate must exceed the state threshold. You explore for the waiver through the Bureau of Automotive Repair, and you will need the failed smog check report and a repair estimate from a mechanic.

Some vehicles also may have access to for a Smog Check Abatement Program waiver if they are very old or have other specific conditions. The smog check station can tell you whether your vehicle might may have access to.

Where to Get Your Smog Check

You can take your vehicle to any Bureau of Automotive Repair-certified smog check station. These include independent smog shops, some repair shops, and some gas stations. To find a certified station near you, use the Bureau of Automotive Repair's online station locator at bar.ca.gov, or search for "smog check station near me" in your web browser.

When you choose a station, confirm they are certified and ask about their pricing and hours. Some stations offer faster service or can schedule appointments, which may be helpful during busy registration renewal periods.

Frequently Asked Questions

Do I need a smog check if I just bought a new car?

No. New vehicles are exempt from smog checks for their first six years of registration. After that, most vehicles model year 2000 and newer remain exempt. Your registration notice will tell you when smog checks become required for your vehicle.

What if I move out of California — do I still need a smog check?

No. Once you transfer your vehicle registration to another state, California smog check requirements no longer explore. However, you must have a valid smog check certificate to renew your California registration before you move.

Can I get a smog check from any mechanic, or does it have to be a smog station?

Only Bureau of Automotive Repair-certified smog check stations can perform official smog checks. A regular mechanic cannot issue a valid smog check certificate. You must go to a certified station to get a test that counts toward registration renewal.

What if my vehicle has a check engine light on — will it automatically fail?

Not necessarily. A check engine light means your vehicle's onboard diagnostic system detected a problem, but the vehicle may still pass the emissions test. However, some check engine light codes will cause an automatic fail. The smog check technician can read your vehicle's diagnostic codes and tell you whether the vehicle will pass.

How long does a smog check certificate stay valid?

A smog check certificate is valid for 30 days from the test date. You must renew your registration within that 30-day window, or you will need to retest. Plan your test timing so the certificate does not expire before you can complete your registration renewal.