What the Smog Check Program Is and Who Has to Do It

California's Smog Check Program requires most vehicle owners to have their cars tested for emissions before they can register or renew registration with the state. The test measures whether your vehicle's exhaust meets California's air quality standards. If you own a vehicle registered in California, you almost certainly need a Smog Check — with a few exceptions for very new cars, electric vehicles, and some motorcycles.

The program exists because California has stricter air quality rules than federal law requires. The test itself takes about 10 to 30 minutes and costs between $30 and $80 depending on your vehicle type and the testing station you choose. You cannot register your vehicle without a passing Smog Check certificate, and you cannot renew your registration without one either.

The test happens at a STAR station — a smog check testing station certified by the state. These are independent repair shops, dealerships, and dedicated testing centers. You can find them by searching the California Bureau of Automotive Repair website or by asking your regular mechanic if they perform Smog Checks.

Key Takeaways

  • Most California vehicles need a Smog Check every two years; vehicles model year 1975 and older, and model year 2000 and newer with fewer than 6,000 miles are exempt.
  • You must pass the test before you can register or renew your vehicle registration with the DMV.
  • The test costs $30 to $80 and takes 10 to 30 minutes at a STAR station, which you can find through the Bureau of Automotive Repair website.
  • If your vehicle fails, you have 30 days to repair it and retest at no additional charge at the same station.
  • You can schedule a test online at many stations, or walk in during business hours.

When You Need a Smog Check and When You Don't

Your vehicle needs a Smog Check every two years when you renew your registration, with some exceptions. Vehicles registered in California for the first time do not need one if they are model year 2000 or newer and have fewer than 6,000 miles on the odometer. Vehicles model year 1975 and older are permanently exempt. Electric vehicles and hydrogen fuel cell vehicles do not need Smog Checks at all.

If you are moving to California from another state and registering your vehicle for the first time, you will need a Smog Check unless your car falls into one of the exempt categories above. If you are renewing your registration and your vehicle is due for a test, the DMV will not process your renewal without a passing certificate.

Some vehicles may be exempt from Smog Check for a limited time. If your vehicle is registered as a classic car, street rod, or kit car, it may have different rules. Check with the Bureau of Automotive Repair or your local DMV office if you are unsure whether your vehicle type is exempt.

How to Find a Testing Station and Schedule Your Test

The California Bureau of Automotive Repair maintains a searchable database of all certified STAR stations on its website. You can search by zip code, city, or station name. The database shows each station's hours, whether they accept walk-ins, and whether they offer online scheduling. Many stations let you book a time slot online; others operate on a first-come, first-served basis.

When you call or visit a station, have your vehicle's license plate number or VIN ready. The station will tell you what type of test your vehicle needs — most cars take the standard OBD test, which reads your vehicle's onboard computer. Older vehicles may need a different test. Ask about the cost upfront; prices vary by station and vehicle type.

You do not need an appointment at most stations, but calling ahead can save you a wait. Bring your vehicle registration or proof of ownership. Some stations may ask for your driver's license as well. The test itself does not require any special preparation — just drive your vehicle to the station and let the technician run the test.

What Happens During the Test and What the Results Mean

The technician will connect your vehicle to a diagnostic machine that reads emissions data from your engine's computer. For most vehicles model year 1996 and newer, this is called an OBD test and takes just a few minutes. The machine checks whether your vehicle's emissions control systems are working properly and whether your exhaust meets state standards.

You will receive a result when ready: either a pass or a fail. A passing certificate is valid for two years and is sent electronically to the DMV. You do not need to print it or bring it anywhere — the DMV can see it in their system when you renew your registration online or in person.

If your vehicle fails, the station will give you a detailed report showing which emissions systems did not meet standards. You have 30 days to repair the vehicle and return to the same station for a retest at no additional charge. If you pass the retest within 30 days, you get your certificate. If you do not retest within 30 days, you must pay the full test fee again at a different station.

What to Do If Your Vehicle Fails the Smog Check

A failing Smog Check usually means your vehicle's emissions control system needs repair. Common reasons include a faulty oxygen sensor, a problem with the catalytic converter, or an engine misfire. The test report will tell you which system failed, but it will not tell you exactly what part needs fixing — that requires a mechanic's diagnosis.

You have 30 days from the test date to repair your vehicle and return to the same STAR station for a free retest. Take the failure report to a mechanic and have them diagnose the problem. Many repairs are straightforward and cost $100 to $500, though some can be more expensive. Ask your mechanic for an estimate before authorizing work.

If you cannot afford the repair right away, you can request a Gross Polluter Abatement Program waiver in some cases. This program allows vehicles that have failed twice and spent at least $500 on repairs to register anyway. You must meet specific income requirements and explore through your local air district. Contact your county's air quality management district to learn whether you may have access to.

How to Register Your Vehicle After Passing the Smog Check

Once you have a passing Smog Check certificate, you can renew your vehicle registration with the California DMV. The certificate is sent electronically to the DMV from the testing station, so you do not need to do anything with the physical certificate. You can renew your registration online through the DMV website, by mail, or in person at a DMV office.

When you renew online or by mail, the DMV will check that your Smog Check certificate is on file. If it is, your renewal will process normally. If you renew in person, bring your registration renewal notice and your driver's license. The DMV staff will verify that your Smog Check is current.

Registration renewal fees vary based on your vehicle's value and age. Smog Check itself does not add to the registration fee — you pay for the test at the STAR station and the registration renewal fee to the DMV separately. Keep your registration renewal notice handy so you know when your Smog Check is due.

Smog Check Requirements for Different Vehicle Types

Most passenger cars, trucks, and SUVs registered in California need a Smog Check every two years. Motorcycles registered in California do not need Smog Checks. Diesel vehicles have the same two-year requirement as gasoline vehicles, but they may use a different testing procedure — ask the STAR station whether they test diesel vehicles before you go.

Vehicles registered as classic cars, street rods, or kit cars may have different Smog Check rules or may be exempt entirely. If your vehicle has a special registration category, contact the Bureau of Automotive Repair or your local DMV office to confirm whether you need a test. Some counties also have local air quality rules that may affect your vehicle, so check with your air district if you live in a non-attainment area.

Commercial vehicles and vehicles registered outside California do not need California Smog Checks. If you move out of state and keep your vehicle registered in California, you will still need a Smog Check when you renew. If you register your vehicle in another state, you will follow that state's emissions testing rules instead.

Frequently Asked Questions

Can I get a Smog Check waiver if I cannot afford to fix my vehicle?

You may be able to get a waiver through the Gross Polluter Abatement Program if your vehicle has failed twice, you have spent at least $500 on repairs, and you meet income requirements. Contact your county's air quality management district to learn whether you may have access to and how the process works. Not all vehicles and not all counties offer this program.

How long does a Smog Check certificate last?

A passing Smog Check certificate is valid for two years from the test date. You must renew your vehicle registration before the certificate expires, or you will need a new test to register again. The DMV will send you a renewal notice about 60 days before your registration expires.

What if I move out of state after passing a Smog Check?

If you register your vehicle in another state, you no longer need California Smog Checks. If you keep your vehicle registered in California while living out of state, you will still need a Smog Check every two years to renew your registration. You can have the test done at any STAR station in California or arrange it when you visit.

Can I test my vehicle at any STAR station, or does it have to be the same one?

You can test at any certified STAR station in California. However, if your vehicle fails, you must return to the same station for your free retest within 30 days. After 30 days, you can test at a different station but will have to pay the full test fee again.

What happens if I register my vehicle without a Smog Check?

The DMV will not process your registration renewal without a passing Smog Check certificate on file. If you try to register without one, your registration will be denied. You must obtain a passing certificate before you can complete the registration process.