California requires a smog check on most gasoline and hybrid vehicles every two years at registration renewal, and also when a vehicle is sold or first registered after coming in from another state. The Bureau of Automotive Repair runs the program, and your DMV renewal notice tells you whether a check is due this cycle and whether you have to use a specific type of station. The California smog check requirements that follow cover who needs one, who’s exempt, what the inspection looks for, what it costs, and what happens if the vehicle fails.
When a Smog Check Is Required
Three situations trigger the requirement.
The first is biennial registration renewal. If your vehicle is registered in an Enhanced or Basic program area, you need a passing smog check every other year to renew. The DMV renewal notice will say so.1California Bureau of Automotive Repair. California Smog Check Program
The second is a change of ownership. When you sell, you’re responsible for giving the buyer a valid smog certification. The station transmits it electronically to the DMV, and it stays valid for 90 days.2State of California Department of Motor Vehicles. Smog Inspections One exception: if the vehicle is less than four model years old, no inspection is needed and the buyer pays an $8 smog transfer fee to the DMV instead.3State of California Department of Motor Vehicles. Registration Fees For 2026, that covers 2022 and newer vehicles.
The third is initial registration of a vehicle previously registered in another state. Those vehicles must pass a smog check before California will register them, regardless of where in the state you live.4Bureau of Automotive Repair. Smog Check Reference Guide
Which Vehicles Are Exempt
Several categories fall outside the program entirely:
- Gasoline vehicles from 1975 and older.1California Bureau of Automotive Repair. California Smog Check Program
- Diesel vehicles from 1997 and older.
- Diesel vehicles over 14,000 pounds GVWR, regardless of model year.
- Electric vehicles.
- Motorcycles.
- Dedicated propane and natural gas vehicles over 14,000 pounds GVWR.5Bureau of Automotive Repair. Smog Check Manual
A separate rule applies to newer vehicles. Vehicles eight model years old or newer skip the biennial inspection but still owe a smog abatement fee at renewal. The first model year that owes an actual inspection is the vehicle’s model year plus eight, so in 2026, vehicles from the 2018 model year and newer are off the inspection hook but still pay the fee.1California Bureau of Automotive Repair. California Smog Check Program
How Program Area Changes What’s Required
California splits the state into three program areas based on local air quality, and your vehicle’s registration address decides which rules apply.
In Enhanced areas, where air quality doesn’t meet federal or state standards, biennial inspections are required and a share of vehicles are directed to STAR-certified stations. Older vehicles in these areas (1976 through 1999) get a loaded-mode emissions test on a dynamometer that measures nitrogen oxides. Basic areas also require biennial inspections, but those older vehicles get a simpler two-speed idle test. Change of ownership areas, which cover more rural parts of the state, only require a smog check when the vehicle is sold or first registered in California — no biennial check at renewal.
For 2000 and newer vehicles, the inspection is the same OBD II-based check in all three area types.4Bureau of Automotive Repair. Smog Check Reference Guide
Where You Can Get the Inspection
California licenses four kinds of smog facilities. Test-and-repair stations do both the inspection and any emissions repairs. Test-only stations do inspections but no repairs, a separation designed to prevent a shop from failing a car to sell work. Repair-only stations handle fixes but don’t inspect. STAR stations are test-and-repair or test-only shops that meet higher performance standards set by BAR.6Bureau of Automotive Repair. Smog Check: When You Need One and Whats Required
Here’s the part that catches people: if your renewal notice says you need a STAR station, you can’t use any other kind. Vehicles identified as high polluters are typically steered there, and if you fail at a STAR station, the retest also has to happen at one.7Bureau of Automotive Repair. Smog Check Inspections
What the Inspection Covers
Every smog check has three parts: a visual inspection, a functional inspection, and an emissions test.
The visual check confirms the required emissions equipment is still there and hasn’t been modified, including items like the catalytic converter and the gas cap. The technician also looks for fuel leaks and visible exhaust smoke.5Bureau of Automotive Repair. Smog Check Manual
The functional check tests the malfunction indicator light (your check engine light) and, on older vehicles with adjustable timing, the ignition timing. For 2000 and newer vehicles, it also evaluates the OBD II system: readiness monitors, stored fault codes, and whether the check engine light is working.
The emissions test itself depends on the vehicle. For most 2000 and newer gasoline vehicles, the inspector plugs into the diagnostic port and reads emissions data from the computer, with no tailpipe measurement. BAR may still require a tailpipe test for 2000-and-newer vehicles without OBD II, those over 14,000 pounds, or vehicles with known OBD II compatibility problems. Vehicles from 1976 through 1999 get a tailpipe test, either loaded-mode on a dynamometer (Enhanced areas) or two-speed idle (Basic and Change of Ownership areas).5Bureau of Automotive Repair. Smog Check Manual
When the vehicle passes, the station transmits a Certificate of Compliance to the DMV electronically. You don’t have to deliver anything on paper.
The “Not Ready” Problem
One of the most common reasons a smog check gets rejected before testing even starts is unset OBD readiness monitors. Your car’s computer runs diagnostic checks on different emissions systems as you drive, and those monitors have to show “ready.” Recent repairs, a disconnected battery, or cleared trouble codes reset them to “not ready.”
California limits how many can be incomplete:
- Gasoline vehicles 1996 through 1999: one unset monitor allowed.
- Gasoline vehicles 2000 and newer: only the evaporative (EVAP) monitor may be unset.
- Diesel vehicles 1998 through 2006: no unset monitors allowed.
- Diesel vehicles 2007 and newer: only the diesel particulate filter and non-methane hydrocarbon catalyst monitors may be unset.
If the monitors aren’t ready, the station rejects the test and you’ve burned the inspection fee for nothing.8Bureau of Automotive Repair. New OBD Readiness Monitor Regulations Explained The fix is to drive the vehicle for several days with a mix of highway and city driving before you bring it in.
What a Smog Check Costs
The inspection fee isn’t set by the state. It varies by station, usually $30 to $70 depending on location and vehicle type, and metro areas and stations near DMV offices tend to run higher. If the vehicle passes, you also pay a state-mandated $8.25 certificate fee that stations have to charge at cost.9Bureau of Automotive Repair. Apply for Repair Assistance Fail, and you skip the certificate fee but still owe the inspection charge. Calling a few local stations before you go is worthwhile since prices can vary noticeably even in the same neighborhood.
If Your Vehicle Fails
A failed smog check means you can’t renew registration until the problem is fixed and the vehicle passes a retest. The station hands you a vehicle inspection report showing what failed, which is the starting point for repairs.6Bureau of Automotive Repair. Smog Check: When You Need One and Whats Required Common culprits include a faulty oxygen sensor, a worn catalytic converter, ignition issues like old spark plugs, evaporative-system leaks, and dirty fuel injectors. On an OBD II vehicle, a lit check engine light with stored codes is an automatic fail.
Check the Federal Emissions Warranty First
Before you pay for an expensive emissions repair, see whether the manufacturer still has to cover it. Federal law requires automakers to warrant emissions control systems for set periods, and the coverage follows the vehicle regardless of whether you bought it new or used.
For passenger cars, light trucks, and medium-duty passenger vehicles, two warranties overlap. The general emissions defect warranty covers defects in materials and workmanship for 2 years or 24,000 miles, whichever comes first. The major components warranty covers catalytic converters, emission control modules, particulate filters, and related components for 8 years or 80,000 miles. If a defect causes a smog failure during the warranty period, the manufacturer has to fix it at no cost, and they can’t deny the claim just because you used an independent mechanic for routine maintenance.10eCFR. 40 CFR 85.2103 – Emission Warranty A catalytic converter on a seven-year-old vehicle with 75,000 miles is still inside that window, and the replacement can easily run $1,000 or more. One phone call to the dealership is worth it.
Help Paying for Repairs or Retiring the Vehicle
If repairs are out of reach financially, the Consumer Assistance Program run by BAR offers two routes. Repair assistance covers emissions-related work at a STAR test-and-repair station for owners whose vehicle failed its biennial smog check and whose household income is at or below 225% of the federal poverty level. The program covers up to $1,450 in repair costs for 1996 and newer vehicles (with a 20% copayment up to $1,812.50 in total costs; above that, you pay the amount over $1,450), and up to $1,100 for 1976 through 1995 vehicles. You still owe anything CAP doesn’t authorize, any non-emissions work, and the $8.25 certificate fee.9Bureau of Automotive Repair. Apply for Repair Assistance
If the vehicle isn’t worth repairing, CAP will also pay you to scrap it, with incentive amounts of $1,350, $1,500, or $2,000 depending on income and whether the vehicle recently failed. The vehicle has to be a passenger vehicle, truck, SUV, or van at 10,000 pounds GVWR or less, and operational enough to drive forward under its own power.11Bureau of Automotive Repair. Retire Your Vehicle
Late Registration Penalties
If a failed smog keeps you from renewing on time, DMV penalties start right away and the DMV doesn’t waive them because you were waiting on repairs:
- 1 to 10 days late: 10% of the vehicle license fee, plus $20.
- 11 to 30 days late: 20% of the vehicle license fee, plus $30.
- 31 days to one year late: 60% of the vehicle license fee, plus $60.
- More than one year: 80% of the vehicle license fee, plus $100.
- More than two years: 160% of the vehicle license fee, plus $200.
The percentages apply to the vehicle license fee and any weight fee due, so on a vehicle with a high license fee the dollars add up quickly.12State of California Department of Motor Vehicles. Penalties Fast action on a failure keeps those costs from stacking on top of the repair bill.
Gross Polluter Notices
Separately from your renewal cycle, California uses roadside remote sensing to spot vehicles with abnormally high emissions on the road. If your vehicle gets flagged as a gross polluter, the state sends a notice requiring an inspection at a designated test-only or STAR-certified station within 30 days. Ignoring the notice triggers a $500 administrative fee that the DMV collects at your next renewal or ownership transfer.13Justia Law. California Health and Safety Code 44080-44086 – Gross Polluters The 30-day window is firm, so a notice like this is one to act on immediately.