What Illinois emissions testing requires

Illinois requires emissions testing for most vehicles registered in Cook County and the collar counties around Chicago (DuPage, Kane, Lake, McHenry, and Will). If you live outside those counties, you do not need to test. The test checks whether your vehicle's exhaust meets state pollution standards — it does not check your brakes, tires, or safety equipment.

You must test every two years, and the test is valid for 24 months from the date you complete it. If you buy a used car in Illinois, you have 30 days to get it tested before you can register it. New vehicles are exempt for their first four years of ownership.

The test itself takes about 10 minutes. A technician connects your vehicle to a machine that reads your engine's emissions data directly from your on-board computer. You do not have to turn anything off or do anything special — the machine does the work.

Key Takeaways

  • Illinois emissions testing is required only in Cook County and the five surrounding collar counties, not statewide.
  • You must test every two years, and the test is valid for 24 months from the date of completion.
  • The test takes about 10 minutes and reads data directly from your vehicle's computer — no special preparation needed.
  • You can find a testing station through the Illinois Environmental Protection Agency website or by calling 1-800-253-5833.
  • If your vehicle fails, you have 30 days to repair it and retest at no additional charge.

Where to find a testing station in Illinois

The Illinois Environmental Protection Agency (IEPA) maintains a list of all licensed testing stations on its website. You can search by your ZIP code to find stations near you. Most stations are independent repair shops, not dealerships, and many are open evenings and Saturdays.

You can also call the IEPA hotline at 1-800-253-5833 to ask for a station in your area. The staff can tell you which stations have the shortest wait times and whether they accept walk-ins or require appointments. Some stations are very busy during certain months — testing is heaviest in the weeks before your registration expires.

The test costs between $25 and $35 depending on your vehicle type and the station. Diesel vehicles, motorcycles, and vehicles over 14,000 pounds have different test procedures and may cost more. Ask the station for the exact price before you arrive.

What happens if your vehicle fails the test

If your vehicle fails, the testing station gives you a printed report showing which emissions standards you did not meet. You have 30 days from the test date to repair the vehicle and return to any testing station for a retest. The retest is free — you pay only if you fail a second time.

Common reasons for failure include a faulty oxygen sensor, a loose gas cap, or a problem with your catalytic converter. Many of these repairs cost $100 to $500, though a catalytic converter replacement can cost more. Before you spend money on repairs, you can take the failure report to a mechanic and ask what they recommend.

If you cannot afford the repair, some nonprofits in Illinois offer help with emissions-related fixes. Contact your local community action agency or call 2-1-1 to ask about repair information programs in your area.

How to prepare your vehicle for testing

You do not need to do much. Make sure your gas cap is tight — a loose cap is one of the most common reasons for failure. Drive your vehicle for at least 20 minutes before the test so the engine reaches normal operating temperature; a cold engine can produce false results.

Bring your vehicle registration and a photo ID. The testing station will record your vehicle identification number (VIN) and mileage. If your check engine light is on, the test will likely fail, so have a mechanic read the code first if you see that light.

You do not need to wash your vehicle, change your oil, or do anything else special. The test reads data from your computer, not from how your car looks or sounds.

When your registration expires and testing important date

Your emissions test must be current before you can renew your vehicle registration. If your registration expires on June 30, your test must be completed by June 30 — a test dated July 1 is too late. The test is valid for 24 months, so plan to test again two years later.

You can test up to 120 days before your registration expires. Many people test early to avoid the rush in the final weeks before expiration. If you test early, your new 24-month period starts from the test date, not from your registration renewal date.

If your registration has already expired and you have not tested, you cannot legally drive the vehicle. Contact the Illinois Secretary of State to renew your registration, and you will need a current test to complete that renewal.

Vehicles exempt from Illinois emissions testing

New vehicles are exempt for their first four years of ownership. Vehicles model year 1995 and older are also exempt. Motorcycles, mopeds, and vehicles registered as antiques or classics have different testing requirements — ask the testing station whether your motorcycle or specialty vehicle needs to test.

Vehicles registered outside the six-county testing area (Cook, DuPage, Kane, Lake, McHenry, and Will) do not need to test at all, even if you drive them into the testing area sometimes. Your registration address determines whether you must test.

If you move out of the testing area, you no longer need to test. If you move into the testing area, you must test within 30 days of registering your vehicle in Illinois.

What to do if you cannot test on time

If you cannot reach a testing station before your registration expires, contact the Illinois Secretary of State to ask about a grace period or temporary registration. Some situations — illness, vehicle breakdown, or station closures — may may have access to you for a short extension, though this is not automatic.

Do not drive with an expired registration. The penalty is a fine, and you will still need to test and renew before you can legally drive again. It is better to call ahead and ask about your options than to wait until after your registration expires.

Frequently Asked Questions

Can I test my vehicle in a different county than where I live?

Yes. You can test at any licensed station in Illinois, even if it is outside your home county. The test result is valid regardless of where you test. However, you must live in one of the six testing counties (Cook, DuPage, Kane, Lake, McHenry, or Will) for testing to be required at all.

What if I just bought a used car and do not know when it was last tested?

You have 30 days from the date you registered it in Illinois to get it tested. If you bought it from a dealer, ask them when it was last tested — they should have that information. If you cannot find out, test it as soon as you can to be safe. A test is valid for 24 months, so if it was tested within the past two years, you may not need to test again right away.

Do I have to test if I only drive my car a few times a year?

Yes, if you live in one of the six testing counties and your vehicle is registered there. The requirement is based on where you live and where your vehicle is registered, not how often you drive. Even if you drive only once a month, you must test every two years to renew your registration.

What if my vehicle has a check engine light on?

The test will likely fail if your check engine light is on. Before you test, take your vehicle to a mechanic and ask them to read the diagnostic code. They can tell you what is wrong and whether it is something you can fix quickly. Once the code is cleared and the light is off, you can test again.

Can I test online or by mail?

No. You must take your vehicle to a licensed testing station in person. The technician needs to connect your vehicle to the testing machine and verify your registration and ID. There is no remote or mail-in option for emissions testing in Illinois.