What Illinois requires and who has to test

Illinois requires an emissions test for most vehicles registered in the state, but the rules depend on where you live and how old your car is. If you live in the Chicago metropolitan area — Cook, DuPage, Kane, Lake, McHenry, or Will County — you must test every two years. If you live anywhere else in Illinois, you must test every two years as well, but the test is less stringent. Vehicles that are model year 1996 or newer must be tested; older vehicles are exempt.

Some vehicles do not need to test at all. Diesel-powered vehicles, motorcycles, and vehicles registered as antiques or classics are not required to have an emissions test. If you have a vehicle that runs on alternative fuel, the rules may differ — contact your local emissions testing station to confirm.

Your vehicle's registration renewal notice will tell you whether a test is required. If the notice says "emissions test required," you must complete the test before you can renew your registration with the Illinois Secretary of State.

Key Takeaways

  • Illinois requires emissions testing every two years for most vehicles model year 1996 and newer, with stricter standards in the Chicago area counties.
  • You must pass the test before renewing your vehicle registration, and the test costs between $25 and $30 depending on your vehicle type.
  • You can find a testing station through the Illinois Environmental Protection Agency website or by calling 1-800-782-7860.
  • If your vehicle fails, you have 30 days to repair it and retest at no additional charge at the same station.
  • Diesel vehicles, motorcycles, antiques, and vehicles registered before 1996 do not require emissions testing in Illinois.

Where to find a testing station and what to bring

Illinois has hundreds of emissions testing stations across the state. You can find one near you through the Illinois Environmental Protection Agency website at www2.illinois.gov/epa, or by calling 1-800-782-7860. The phone line can tell you which stations are open, their hours, and whether they have same-day appointments available.

When you go to test, bring your vehicle registration and a valid photo ID. Some stations accept walk-ins, but many require an appointment — call ahead to confirm. The test itself takes about 15 to 30 minutes. The station will connect your vehicle to a machine that measures tailpipe emissions and checks your on-board diagnostic system.

Testing stations are run by private businesses under contract with the state, so hours and appointment policies vary. If one station is fully booked, another nearby station may have openings the same day.

What the test measures and why your vehicle might fail

The emissions test measures two main things: the gases coming out of your tailpipe and the status of your vehicle's diagnostic system. The machine checks for nitrogen oxides, particulate matter, and other pollutants. It also reads your vehicle's on-board diagnostic computer to see whether any emissions-related warning lights are on or whether the system has detected a problem.

Vehicles fail most often because the check engine light is on, because the diagnostic system has not been cleared, or because the vehicle is running too rich (burning too much fuel). A vehicle can also fail if the gas cap is loose or missing — a loose cap triggers a diagnostic code that causes failure. Before you test, make sure your gas cap is tight and your check engine light is off.

If your vehicle has a serious mechanical problem — a faulty oxygen sensor, a failing catalytic converter, or a major engine leak — it will fail. These repairs can be expensive, but they also mean your vehicle is producing harmful emissions that affect air quality.

The cost and what happens if you fail

An emissions test costs between $25 and $30 in most of Illinois, depending on whether your vehicle is a passenger car, SUV, or truck. Some stations charge slightly different amounts, but the state caps the price. You pay at the testing station, and the results are sent directly to the Illinois Secretary of State's office.

If your vehicle passes, you receive a certificate or a number you can use to renew your registration when ready. If your vehicle fails, you have 30 days to repair it and return to the same station for a retest at no additional charge. You do not have to pay again if you retest within 30 days at the station where you originally failed.

If you do not retest within 30 days, you will need to pay the full testing fee again at a different station. After 30 days, the failed test expires and you start over.

How to prepare your vehicle before testing

Before you go to a testing station, do a few straightforward checks. Make sure your gas cap is tight — a loose cap is one of the most common reasons for failure and is free to fix. Check that your check engine light is off. If it is on, you can try disconnecting your battery for 15 minutes to clear the code, though this does not always work if there is an actual problem.

Make sure your vehicle has been driven recently. A vehicle that has been sitting for weeks may not pass because the diagnostic system has not completed its self-check cycle. Drive your car for at least 20 minutes on the highway before testing to warm up the engine and allow the system to run through its checks.

If you know your vehicle has a problem — a rough idle, poor acceleration, or visible smoke — have it looked at before testing. A mechanic can often identify and fix the issue for less than the cost of a failed test and a retest.

Chicago area testing versus downstate testing

The six counties in the Chicago metropolitan area — Cook, DuPage, Kane, Lake, McHenry, and Will — have stricter emissions standards than the rest of Illinois. Vehicles in these counties must meet tighter pollution limits, and the test is more rigorous. If you live in one of these counties and your vehicle barely passes the downstate standard, it may fail the Chicago area test.

If you live in the Chicago area and your vehicle fails, the same 30-day retest window applies. However, you must retest at a station in the Chicago area, not downstate. The testing station will know which standard applies to your vehicle based on your registration address.

Downstate Illinois has a less stringent test, but vehicles still must meet federal emissions standards. The difference is mainly in how strictly the test measures those standards.

What to do if your vehicle fails and repair costs are high

If your vehicle fails and the repair is expensive, you have a few options. First, get a written estimate from a mechanic before deciding whether to repair. Some repairs — like replacing a gas cap or clearing a diagnostic code — cost almost nothing. Others, like replacing a catalytic converter, can cost $500 to $1,500.

If the repair cost is very high relative to your vehicle's value, you may want to explore whether your vehicle is may be able to access for a state repair information program. Illinois does not currently have a statewide vehicle repair information program, but some counties and nonprofits offer help. Call 2-1-1 to ask whether your county has a program.

If you cannot afford the repair, you cannot legally register your vehicle in Illinois until it passes. However, you can continue to drive it while the 30-day retest window is open. After 30 days, you must either repair it or stop driving it.

Frequently Asked Questions

Can I renew my registration if I have not taken the emissions test yet?

No. The Illinois Secretary of State will not process a registration renewal without a passing emissions test result if your vehicle requires one. You must complete the test before your registration expires. If your registration has already expired, you can still test and renew, but you may face a late fee.

What if I move to a different county in Illinois?

Update your registration address with the Illinois Secretary of State. Your new address determines which emissions standard applies to your vehicle. If you move from downstate to the Chicago area, your vehicle will need to meet the stricter standard on your next test. If you move from the Chicago area downstate, the standard becomes less strict.

Do I have to test if my vehicle is brand new?

New vehicles are exempt from emissions testing for the first four years of registration. After that, testing is required every two years. Check your registration renewal notice to see when your vehicle first becomes subject to testing.

What if the testing machine breaks down while my vehicle is being tested?

If a technical problem occurs during your test, the station will reschedule you at no charge. You are not responsible for equipment failure. Ask the station for a written note of the failed appointment so you have proof if you need to explain a delay to the Secretary of State's office.

Can I test my vehicle in a different county than where it is registered?

No. You must test at a station in the county where your vehicle is registered. The testing station verifies your registration address and applies the correct emissions standard for your location. If you test in the wrong county, the result may not be accepted.