California Emissions: Smog Check Rules, Exemptions, and Penalties

California smog check rules require most gasoline, hybrid, and alternative-fuel vehicles from model year 1976 onward, and most diesel vehicles from model year 1998 onward with a gross vehicle weight rating of 14,000 pounds or less, to pass an emissions inspection at a licensed station every two years at registration renewal. You also need one when you sell the vehicle privately and when you first register it in California. Without a passing certificate, the DMV will not renew your registration.¹

Which Vehicles Need a Smog Check

The program covers gasoline, hybrid, and alternative-fuel vehicles of model year 1976 and newer, and diesel vehicles of model year 1998 and newer with a GVWR of 14,000 pounds or less.¹

Where you live matters too. California splits the state into enhanced areas and change-of-ownership-only areas based on air quality. In enhanced areas, which include most major metropolitan counties, you need an inspection at every biennial renewal. In change-of-ownership-only areas, you generally only need one when the vehicle is sold or first registered in-state. Your DMV renewal notice tells you whether a smog check is due this cycle.²

Vehicles That Are Exempt

Several categories skip the biennial inspection:¹

Gasoline vehicles eight model years old or newer. Instead of a smog check, you pay an annual smog abatement fee with registration renewal until the vehicle ages into the program.²
Gasoline vehicles model year 1975 or older. Fully exempt from both the inspection and the abatement fee.
Diesel vehicles model year 1997 or older.
Diesel vehicles over 14,000 pounds GVWR. These fall under CARB’s separate Clean Truck Check program instead.
Natural gas vehicles over 14,000 pounds.
Electric vehicles.
Motorcycles.

Even an exempt newer vehicle can be pulled in for an out-of-cycle inspection if CARB’s remote sensing or other monitoring suggests an emissions problem.

What the Inspection Involves

Smog checks must be done at a licensed Smog Check station. For model year 2000 and newer vehicles, the inspection has three parts: a functional check of the onboard diagnostics (OBD II) system, a visual inspection of emissions control components, and a gas cap pressure test. The OBD II check reads fault codes from the vehicle’s computer to confirm emissions systems are working.¹

Older vehicles, model years 1976 through 1999, may also need a tailpipe emissions test, depending on the model year and county. Expect to pay somewhere between $30 and $50 at a standard station, though prices vary. If you pass, the station transmits the certificate electronically to the DMV, and it is valid for 90 days.¹

STAR Stations and Directed Vehicles

Not every station can inspect every vehicle. The Bureau of Automotive Repair uses a statistical model called the Profile to flag vehicles likely to fail. Those vehicles, together with a 2% random sample used for program evaluation, are directed to STAR-certified stations. Vehicles previously identified as gross polluters must also go to a STAR station. Your DMV renewal notice tells you if your vehicle has been directed.

STAR stations meet higher equipment and training standards and can provide state-subsidized emissions repairs through the Consumer Assistance Program. If you have been directed to a STAR station, a regular shop cannot certify your vehicle, though it can still do the mechanical repairs before you take the car to a STAR station for the official test.

Buying or Selling a Vehicle

If you sell a vehicle privately, you are legally responsible for providing the buyer with a valid smog certification before the sale, and the vehicle must have passed within the last 90 days. As a buyer, ask for the inspection report before you hand over money.¹

Vehicles four model years old or newer are the exception. No smog check is needed at change of ownership; the new owner pays a one-time $8 smog transfer fee to the DMV instead.³ Dealers handle certification as part of the sale and can charge up to $50 for testing plus the actual certification fee.

Bringing a Vehicle from Out of State

Moving to California with your car? It needs a smog check to complete initial California registration. There is also a catch for “49-state” vehicles, which were built to federal rather than California emissions standards. If such a vehicle has fewer than 7,500 miles on the odometer, you generally cannot register it in California unless you qualify for a specific exemption.⁴

Those exemptions include inheriting the vehicle, receiving it in a divorce, or buying it out of state as an emergency replacement for a California-registered vehicle that was damaged, totaled, or stolen while you were traveling. A 49-state vehicle with 7,500 miles or more is not subject to the restriction. It still needs a standard smog check and a vehicle verification inspection, but it does not have to be retrofitted to California certification standards.

If Your Vehicle Fails

A failed smog check blocks registration until the problem is fixed and the vehicle passes a retest. The underlying issue might be as simple as a loose gas cap or as expensive as a failing catalytic converter.

The Bureau of Automotive Repair’s Consumer Assistance Program offers two forms of help:⁵

Repair assistance. If your vehicle is model year 1996 or newer and you meet income eligibility, you can receive up to $1,450 toward emissions-related repairs at a STAR-certified station.⁶
Vehicle retirement. CAP will pay you to scrap a vehicle that fails. Income-eligible owners can receive up to $2,000; owners who do not meet the income limits can receive up to $1,350.

Retirement is worth running the numbers on for older cars with expensive emissions problems. A $2,000 car that needs $1,800 in repairs is a losing proposition, and the retirement payment lets you walk away without pouring money into it.

Penalties for Letting Registration Lapse

Because you cannot renew registration without a passing smog certificate or an exemption, skipping the inspection effectively means driving on expired tags. California’s late penalties stack a percentage of the vehicle license fee onto flat registration and CHP late fees, and they climb fast:³

1 to 10 days late: 10% of the vehicle license fee, plus $20 in flat fees.
11 to 30 days late: 20% of the vehicle license fee, plus $30 in flat fees.
31 days to one year late: 60% of the vehicle license fee, plus $60 in flat fees.
One to two years late: 80% of the vehicle license fee, plus $100 in flat fees.
More than two years late: 160% of the vehicle license fee, plus $200 in flat fees.

On a vehicle with a $300 annual license fee, letting registration lapse for six months adds roughly $240 in penalties on top of the renewal itself. California law also prohibits driving an unregistered vehicle on public roads, so a traffic stop for anything else can trigger an added citation for expired registration. A registration-only violation generally cannot be the sole basis for enforcement during the first month after expiration.⁷

Tampering with Emissions Equipment

Removing, disabling, or modifying emissions control equipment is illegal under both state and federal law. California Vehicle Code Section 27156 prohibits installing a device that alters emissions controls and bars operating a vehicle with tampered equipment. Courts must impose the maximum fine and cannot suspend any portion of it when the violation is willful.⁸ On the federal side, the Clean Air Act prohibits manufacturing, selling, or installing aftermarket defeat devices, with civil penalties up to $25,000 per violation for manufacturers and dealers and up to $2,500 for other individuals.⁹ The practical result: delete kits and tunes that remove diesel particulate filters or catalytic converters will cause a smog check failure and make the vehicle effectively unregistrable in California.

Heavy-Duty Trucks Follow Different Rules

If your vehicle has a GVWR over 14,000 pounds, it falls outside the Smog Check Program but not outside emissions regulation. CARB’s Clean Truck Check program requires periodic emissions compliance testing for nearly all diesel and alternative-fuel heavy-duty vehicles operating on California roads, including trucks registered in other states.¹⁰ Emissions compliance testing requirements took effect on October 1, 2024, with testing deadlines starting January 1, 2025, and most covered vehicles are subject to semi-annual testing.¹¹

1
Bureau of Automotive Repair. Smog Check Requirements
2
California DMV. Smog Inspections
3
California DMV. Registration Fees
4
California Department of Motor Vehicles. California Noncertified/Direct Import Vehicle Exemptions
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Bureau of Automotive Repair. Consumer Assistance Program
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Bureau of Automotive Repair. Apply for Repair Assistance
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California Legislative Information. California Vehicle Code 4000
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California Legislative Information. California Vehicle Code 27156
9
U.S. Environmental Protection Agency. National Enforcement and Compliance Initiative: Stopping Aftermarket Defeat Devices for Vehicles and Engines
10
California Air Resources Board. Clean Truck Check – Overview Fact Sheet
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California Air Resources Board. Clean Truck Check – Emissions Compliance Testing Requirements