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The bottom line: Emissions testing (also called smog testing) is a mandatory vehicle inspection that measures the pollutants your car releases into the atmosphere.
If you’re selling a car, you usually don’t need to provide a passing test to the buyer. California is the main exception, and specific metro areas of Georgia and Missouri also require sellers to provide a certificate.
Testing costs typically range from $15 to $50. Most cars pass without issues. If your car fails and repairs cost more than it’s worth, services like Peddle and Wheelzy will buy it with a failed emissions test.
Key Takeaways
- Emissions testing measures harmful pollutants from your exhaust, including carbon monoxide, hydrocarbons, and nitrogen oxides.
- About half of U.S. states require emissions testing, but most only in specific metro areas, not statewide.
- Only California requires all private sellers to provide a passing smog certificate. Parts of Georgia (Atlanta metro) and Missouri (St. Louis area) also require it in specific counties.
- If your car fails, you can still drive it temporarily, but you can’t renew your registration until it passes.
and
buy cars with failed emissions tests as-is, with no repairs needed before you sell.
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Emissions Testing Basics
What is emissions testing?
Think of emissions testing as a health check for your car’s exhaust system. Your car gets tested to make sure it’s not polluting the air beyond legal limits.
The test measures harmful substances that come out of your tailpipe, including carbon monoxide, hydrocarbons, nitrogen oxides, and particulate matter.
The modern emissions testing system expanded under the Clean Air Act of 1990, which required states with poor air quality to set up inspection programs. The goal was simple: make sure vehicles meet environmental standards to keep the air cleaner.
Smog vs. emissions testing
“Smog testing” and “emissions testing” are the same thing. California and western states tend to use the term “smog testing,” while most other places call it “emissions testing.”
Either way, you’re getting the same inspection.
How does the test work?
For 1996 and newer vehicles, the technician plugs a scanner into your car’s diagnostic port, usually located under the dashboard near the steering wheel. This is called OBD-II testing. It typically takes just 5 to 10 minutes.
For older vehicles, a probe is inserted into the tailpipe to directly measure what’s coming out. The whole process typically takes 15 to 30 minutes.
You’ll walk away with either a passing certificate or a report showing what needs to be fixed.
Do Sellers Have to Provide an Emissions Test?
In most states, sellers don’t need to provide a passing emissions certificate. The responsibility falls on the buyer, who must pass testing before they can register the car in their name.
There are three notable exceptions. In these places, sellers are legally required to provide a certificate at the time of sale:
| State / Area | What Sellers Must Know |
|---|---|
| California (statewide) | Sellers must provide a valid smog certificate (within 90 days) for most gasoline vehicles older than 4 model years. Newer cars only require a transfer fee. |
| Georgia (13-county Atlanta metro) | Sellers in Cherokee, Clayton, Cobb, Coweta, DeKalb, Douglas, Fayette, Forsyth, Fulton, Gwinnett, Henry, Paulding, and Rockdale counties must ensure a passing test at the time of sale. |
| Missouri (St. Louis metro area) | Private sellers in the St. Louis I/M area must provide a passing emissions certificate less than 60 days old at the time of sale. |
In all other states, even where emissions testing programs exist, the buyer must ensure the vehicle passes before they can register it. You’re not legally required to provide a test certificate to complete the sale.
Which States Have Emissions Testing Programs?
About half of U.S. states require emissions testing for vehicle registration, but most only in specific metro areas. States with programs include Arizona (Phoenix and Tucson), California, Colorado (Denver metro), Connecticut, Delaware, Georgia (Atlanta area), Illinois (Chicago metro), Indiana (northwest counties), Louisiana (Baton Rouge area), Maine (Portland area), and Maryland.
Also included are Massachusetts, Missouri (St. Louis area), Nevada (Las Vegas and Reno), New Hampshire, New Jersey, New Mexico (Albuquerque), New York, North Carolina (48 urban counties), Ohio (Cleveland and Akron area), Oregon (Portland and Medford areas), Pennsylvania (25 counties), Rhode Island, Texas (17 counties), Utah (5 counties), Vermont, Virginia (Northern Virginia), and Wisconsin (southeast counties).
Texas made a notable change in January 2025, eliminating the general vehicle safety inspection requirement. The emissions test requirement still applies in 17 specific counties, including the Dallas-Fort Worth, Houston, Austin, and El Paso metro areas.
Where is emissions testing not required?
The following states have no emissions testing program at all: Alabama, Alaska, Arkansas, Florida, Hawaii, Idaho, Iowa, Kansas, Kentucky, Michigan, Minnesota, Mississippi, Montana, Nebraska, North Dakota, Oklahoma, South Carolina, South Dakota, Tennessee, Washington, West Virginia, and Wyoming.
Some of these states had programs in the past but ended them. Tennessee ended its metro county program in 2022, and Washington ended its program in 2020.
Idaho ended its program in 2023. Alaska also discontinued programs in the Anchorage and Fairbanks areas in the early 2010s.
How Much Does an Emissions Test Cost?
The test itself is affordable in most states. Costs typically run $15 to $50 depending on where you live. Here are some examples by state:
| State | Typical Test Fee | Notes |
|---|---|---|
| California | $25 to $50 | Varies by region and station type |
| Colorado | $15 to $25 | $25 for 1982 and newer; $15 for 1981 and older |
| Texas | ~$25 | Only required in 17 counties |
| Virginia | ~$30 | Northern Virginia counties only |
| Arizona | $15 to $25 | Phoenix and Tucson metro areas only |
The real expense comes if your vehicle fails the test. Repair costs can range from as little as $20 for a new gas cap to over $3,500 for a failed catalytic converter. The most common repairs fall into three categories:
| Repair Category | Typical Cost | Common Examples |
|---|---|---|
| Simple fixes | Under $100 | Loose or damaged gas cap, dirty air filter, overdue oil change, loose connections |
| Mid-range repairs | $100 to $500 | Oxygen sensors, spark plugs, minor exhaust leaks, EVAP system problems |
| Major repairs | $950 to $3,500+ | Catalytic converter replacement, major exhaust system work, engine computer issues |
Not sure if repairs are worth it? Get a free repair estimate from RepairPal to compare repair costs against your car’s actual value before deciding.
Preparing Your Vehicle for the Emissions Test
Most well-maintained vehicles pass emissions testing without any issues. The key is knowing what to check before you go.
- The check engine light is your enemy. If that light is on, your car will fail automatically. Don’t try to reset it by disconnecting the battery. Modern cars will flag that as a problem too. Get the underlying issue fixed first.
- Basic maintenance makes a big difference. An oil change can literally be the difference between passing and failing if your oil is dirty and overdue. A clogged air filter forces your engine to work harder and can push emissions over the limit.
- Timing matters more than you think. Don’t show up with a cold engine. Drive your car for at least 20 minutes before the test. The catalytic converter needs to be hot to work properly.
- Recent repairs can cause problems. If you’ve had your battery disconnected or major engine work done recently, your car’s computer may not be ready for testing. You may need to drive 100 to 200 miles under varied conditions before the monitoring systems finish their checks.
Learn more: When Is It Not Worth Repairing a Car? (Sell vs. Fix)
What Happens When Your Car Fails Emissions Testing?
- You can still drive, at least temporarily. Failing an emissions test doesn’t mean your car gets impounded. You won’t be able to renew your registration until you fix the problem, which eventually means you can’t legally drive it.
- Most states offer a free retest within 30 days if you return to the same facility. Some states extend this to any licensed facility, not just the original one.
- Financial help may be available if repairs are expensive. Many states have waiver programs if you spend a set amount on emissions-related repairs and your car still fails. For example, Georgia’s repair threshold for 2025 is $1,146 and Wisconsin’s is $1,110. These amounts are adjusted each year.
- Temporary permits can keep you legal while making repairs. Most states offer 30-day temporary permits that let you drive to work and get repairs done without getting a ticket for expired registration.
Vehicle Age and Emissions Test Results
Age is the biggest factor in emissions test failures, but it’s not just about the model year.
- Newer cars rarely fail. Vehicles less than 4 years old have very low failure rates, which is why many states exempt them. Modern engines with computer controls and advanced emissions systems are remarkably clean.
- The risk zone starts around 8 to 10 years. Oxygen sensors typically last 7 to 10 years, and catalytic converters often need replacement around the 10 to 15 year mark in high-mileage vehicles.
- Maintenance history matters more than age alone. A well-maintained 15-year-old car may pass easily, while a neglected 8-year-old car could fail. Regular oil changes, tune-ups, and addressing check engine lights promptly make a big difference.
- High-mileage vehicles face extra scrutiny because wear affects emissions systems. However, highway miles are generally easier on emissions equipment than city driving with lots of stop-and-go traffic.
Read more: How to Identify Car Problems (If You’re Not a Car Person)
Selling a Car That Won’t Pass Emissions Testing
Sometimes you’ll need to sell a car that won’t pass emissions. Maybe the repairs cost more than the car is worth. You do have options.
- Full disclosure protects you. If you know your car has emissions problems, document everything in writing. A clear written statement that the buyer understands the vehicle’s emissions issues is your best protection.
- Price adjustments make deals work. Most buyers will consider a car with known emissions problems if the price reflects the needed repairs. Get repair estimates and reduce your asking price accordingly.
- Know your state’s “as-is” rules. California requires a passing test (or a “certificate of noncompliance”) even for as-is sales. Most other states allow private as-is sales with full disclosure. Confirm your local rules with the DMV before selling.
- Consider instant offer buyers. Someone buying a car for parts, or a buyer in a state with no emissions requirements, may be happy with a car that won’t pass testing. Peddle and Wheelzy will buy your car with a failed emissions test.
Your Action Plan
If you’re planning to sell a car in a state that requires emissions testing, here’s what to do:
- Start early. Test your vehicle 4 to 6 weeks before you plan to sell. This gives you time to fix problems without rushing or losing buyers while you wait for repairs.
- Check your state’s current requirements. Use the information above as a starting point, but confirm current rules with your state’s DMV. Requirements can change.
- Get your paperwork in order. Keep your current vehicle registration, any previous emissions certificates, and repair receipts if you’ve had emissions-related work done.
- Have a backup plan. Know what you’ll do if your car fails testing. Will you make the repairs, sell it to an online junk car buyer, or consider other options?
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Frequently Asked Questions
What cars are exempt from emissions testing?
Exemptions vary by state, but most states exempt new vehicles for the first 3 to 7 model years. Very old vehicles (typically 25 years and older) are usually exempt too, as they’re treated as classics.
Electric vehicles are universally exempt since they produce zero tailpipe emissions. Diesel trucks over a certain weight, motorcycles, and low-speed vehicles are also commonly exempt.
Check your state’s specific DMV website to confirm what applies to your vehicle.
How long is an emissions test certificate valid?
It depends on the state. California certificates are valid for 90 days. Nevada certificates are valid for 90 days for private sales, and 180 days if the vehicle was purchased from a licensed dealer.
In most other states, the test is tied to your registration renewal cycle, so it stays valid for one to two years depending on how often your state requires testing.
Are electric cars exempt from emissions testing?
Yes. Electric vehicles are exempt from emissions testing in every state that has a testing program. Since they produce zero tailpipe emissions, there’s nothing to test.
Plug-in hybrids may still be subject to testing in some states since they have a combustion engine. Check your state’s DMV for specifics if you’re selling a plug-in hybrid.
What does “not ready” mean on an emissions test?
“Not ready” means your car’s onboard computer hasn’t finished running its self-checks since the last reset. This happens after a battery disconnect, code clearing, or major engine work.
The fix is simple but takes time. Drive the car through varied conditions, including highway speeds and city stop-and-go, for roughly 100 to 200 miles.
This allows the monitoring systems to complete their cycles. Then return for the test.
Learn more: How to Sell a Junk Car
Can I sell my car if it has a failed emissions test?
Yes, in most states. Outside of California, Georgia (Atlanta metro), and Missouri (St. Louis metro), you’re not legally required to fix emissions problems before selling.
Disclose the issue in writing and adjust your price to reflect the needed repairs.
If repairs cost more than the car is worth, instant offer buyers like Peddle and Wheelzy purchase cars as-is with failed emissions tests.
You can compare offers from multiple services with Sell Car Advisor to see who pays the most for your specific vehicle.
Article Update History
State seller requirements fact-checked against official emissions testing program websites.
Originally posted and shared with our readers.