What an emissions check measures and why your state requires it

An emissions check is a test that measures how much pollution your vehicle's exhaust produces. The test plugs into your car's onboard diagnostic system (usually under the steering wheel or dashboard) and reads whether your engine is burning fuel cleanly and whether your emissions control systems are working.

States require emissions checks because the Clean Air Act sets national air quality standards. Your state's environmental agency decides whether your county or region needs the test based on whether the air meets those standards. If your area has poor air quality, emissions testing is mandatory. If your area's air quality is good, your state may not require it at all.

The test itself takes 10 to 30 minutes and costs between $20 and $75 depending on your state and vehicle type. Some states charge more for trucks or vehicles with diesel engines. The fee goes to the testing station, not to the state.

Key Takeaways

  • An emissions check reads your vehicle's pollution output through the onboard diagnostic port and takes 10 to 30 minutes.
  • Your state requires emissions testing only if your county or region has air quality problems, so not all states or all areas within a state need it.
  • You must pass the test to renew your vehicle registration in states that require it, and a failed test means you cannot register until repairs are made.
  • If your check engine light is on, your vehicle will fail the test, so have that repaired before you go.
  • You can find testing stations through your state's environmental agency website or by searching your state name plus "emissions testing locations".

Where emissions checks are required and where they are not

Emissions testing is required in about half of U.S. states, concentrated in areas with air quality problems. California, New York, Texas, Illinois, Pennsylvania, Ohio, and Colorado all require it in certain counties. Some states require it statewide; others only in major cities or regions that fail federal air quality tests.

If you live in a state that does not require emissions testing, you do not need one to register your vehicle. If you move to a state that does require it, you will need to pass a test before you can register your vehicle there. Your previous state's test results do not transfer.

The easiest way to find out whether your state requires it is to visit your state's environmental agency website or your state's vehicle registration website. Both will tell you whether testing is required in your county. You can also call your local DMV or registration office and ask directly.

How to prepare your vehicle for an emissions check

Before you go to a testing station, check your check engine light. If it is on, your vehicle will fail the test. Have the problem diagnosed and repaired first. A mechanic can read the code for $50 to $100, and repairs can range from replacing a gas cap (sometimes free) to fixing a catalytic converter (often $500 to $2,000).

Make sure your vehicle has been driven recently. Some testing stations require that your engine be warm when you arrive, and many require that you have driven at least 50 miles since your last engine restart. This allows the emissions control system to run through its full cycle.

Bring your vehicle registration and proof of insurance. Some states also require a photo ID. Call the testing station ahead of time to confirm what documents they need and whether you should make an appointment. Many stations accept walk-ins, but some are appointment-only.

What happens if your vehicle fails the emissions check

If your vehicle fails, the testing station will give you a report that identifies which emissions standards your vehicle did not meet. The report will say whether the problem is with your engine, your fuel system, or your emissions control equipment (like your catalytic converter or oxygen sensors).

You cannot register your vehicle until you fix the problem and pass a retest. In most states, you have 30 to 60 days to repair and retest. Some states allow one free retest; others charge the full fee again. Check your state's rules on your environmental agency website.

Take the failure report to a mechanic and ask them to diagnose the specific problem. Not all mechanics can repair all emissions issues, so ask whether they have experience with the type of failure you received. Get a repair estimate before you agree to work.

The difference between emissions checks and safety inspections

An emissions check tests only pollution output. A safety inspection tests brakes, lights, steering, tires, and other equipment that affects whether your vehicle is safe to drive. Some states require both; some require only one; some require neither.

These are separate tests done at separate times, often at different locations. An emissions check plugs into your diagnostic port. A safety inspection is a physical walk-around where a technician checks your equipment. You can fail one and pass the other.

Your state's registration website will tell you which tests are required in your state. Do not assume that because you need one, you need the other.

How to find a testing station and schedule a test

Your state's environmental agency maintains a list of authorized emissions testing stations. Search your state name plus "emissions testing locations" or go directly to your state's environmental or air quality website. Most states have a searchable map or list organized by county.

Call ahead to confirm the station is open, ask what documents you need to bring, and find out whether they require an appointment. Some stations are first-come, first-served; others book appointments weeks in advance. If you need a retest after a repair, ask whether the same station will retest you or whether you can go anywhere on the approved list.

Bring your vehicle registration, proof of insurance, and a photo ID. Arrive with a warm engine and at least 50 miles of recent driving. The test itself takes 10 to 30 minutes, and you will get your results the same day.

What to do if you cannot pass the emissions check

If your vehicle repeatedly fails after repairs, ask your mechanic whether the problem is fixable or whether the repair cost exceeds the vehicle's value. In some states, if your repair bill would exceed a certain percentage of your vehicle's value (often 7 to 10 percent), you may be able to get a waiver that lets you register without passing.

Contact your state's environmental agency to ask about hardship waivers or repair information programs. Some states offer low-interest loans or rebates for emissions repairs on older vehicles. Some offer vouchers that let you use a certified mechanic at no cost.

If you cannot repair the vehicle, you may be able to scrap it through a vehicle recycling program. Some states offer cash or tax credits for scrapping vehicles that cannot pass emissions. Ask your state's environmental agency whether this option exists in your state.

Frequently Asked Questions

Can I get an emissions check waived if I just moved to a state that requires it?

No. If your new state requires emissions testing, you must pass a test to register your vehicle there. Your previous state's test results do not count. However, if your vehicle is brand new or has very low mileage, some states exempt it for the first few years.

What if my vehicle has a check engine light that is not related to emissions?

Your vehicle will still fail the test. The testing station cannot tell whether the light is for an emissions problem or something else. You must have the code read and the problem fixed before you retest, even if it is unrelated to pollution.

Do I have to use the same testing station for my retest?

No. You can use any authorized station on your state's approved list. However, some stations may ask to see your original failure report. Keep that document until you pass.

How often do I need an emissions check?

In most states that require it, you need one every one or two years, usually when you renew your vehicle registration. Your registration paperwork will tell you when your next test is due. Some states test every year; others every two years.

What if I move out of state after I pass an emissions check?

Your test result does not transfer to your new state. If your new state requires emissions testing, you will need to pass a test there before you register your vehicle. If your new state does not require it, you do not need one.