What Illinois requires for emissions testing

Illinois requires emissions testing 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 do not need an emissions test at all, though you still need a safety inspection.

Your vehicle must pass an On-Board Diagnostic (OBD) test, which reads your car's computer to check emissions systems. The test takes about 10 minutes and costs roughly $15 to $30, depending on the testing station. Diesel vehicles, motorcycles, and cars older than 1996 are exempt from the OBD requirement, though some older vehicles may need a different type of test.

You cannot register or renew your vehicle registration in Illinois without a passing emissions test result — if you live in a county that requires it. The test result is valid for two years from the date you pass, and you must complete it before your registration expires.

Key Takeaways

  • Emissions testing is required only in Cook, DuPage, Kane, Lake, McHenry, and Will counties; all other Illinois counties do not require it.
  • The test reads your vehicle's computer for emissions system problems and takes about 10 minutes at any state-certified testing station.
  • You must pass before you can renew your vehicle registration, and the result stays valid for two years.
  • If your vehicle fails, you have 30 days to repair it and retest at no additional cost at the same station.
  • You can find certified testing stations through the Illinois Environmental Protection Agency website or by calling your local Secretary of State office.

Where to find a testing station in Illinois

The Illinois Environmental Protection Agency (IEPA) maintains a searchable list of certified emissions testing stations on its website. You can search by county or ZIP code to find stations near you. Most stations are independent repair shops, quick-lube facilities, or dealerships that have been certified to perform the test.

Call ahead before you go. Testing stations have different hours, and some may have a wait during peak times. Ask whether they can test your specific vehicle type — most test gasoline vehicles, but not all test diesel or hybrid models. You can also contact your local Secretary of State office, which keeps a list of stations in your area.

What to bring and how the test works

Bring your vehicle registration and a valid photo ID. The technician will connect a scanner to your vehicle's OBD port, usually located under the steering column or dashboard. The scanner reads your vehicle's emissions control system data and checks whether it meets Illinois standards.

The test does not require you to turn off your engine or leave the vehicle. The technician performs the scan while your car is parked, and the whole process takes 5 to 15 minutes. You will receive a printed result when ready — either a pass or a fail. If you pass, the station sends the result electronically to the Illinois Secretary of State, and you can renew your registration right away.

What happens if your vehicle fails

If your vehicle fails the emissions test, you have 30 days to repair the problem and retest at no additional charge at the same station. The technician will give you a report showing which emissions systems failed. Common failures include a faulty oxygen sensor, a loose gas cap, or problems with the catalytic converter.

Take the failure report to a repair shop — it does not have to be the same station where you tested. The repair shop uses the report to diagnose and fix the problem. Once repaired, return to the testing station within 30 days for a free retest. If you pass the second time, the result is sent to the Secretary of State and you can renew your registration.

If you cannot afford the repair, some nonprofits and community programs offer help with emissions-related repairs for low-income vehicle owners. Contact your local community action agency or ask the testing station whether they know of any information programs in your area.

Renewing your registration after a passing test

Once you have a passing emissions test result, you can renew your vehicle registration through the Illinois Secretary of State. You can renew online at cyberdriveillinois.com, by mail, or in person at a local Secretary of State office. You will need your vehicle registration renewal notice, proof of insurance, and the emissions test result.

If you tested at a certified station, the result is usually sent electronically to the Secretary of State within 24 hours, so you may not need to bring a paper copy. However, it is a good idea to keep your receipt from the testing station in case there is a delay in the electronic transmission.

Emissions testing important date and expiration

Your emissions test result is valid for two years from the date you pass. Your vehicle registration renewal notice will show your expiration date. You must complete the test before your registration expires — you cannot test after expiration and then renew retroactively.

If your registration has already expired, you must renew it first before you can test. Contact your local Secretary of State office for instructions on renewing an expired registration. Testing stations cannot test vehicles with expired registrations, so do not wait until the last minute.

Vehicles exempt from Illinois emissions testing

Diesel vehicles, motorcycles, and gasoline vehicles manufactured before 1996 do not need an OBD emissions test. However, all vehicles in Illinois still need a safety inspection to register or renew registration. The safety inspection checks brakes, lights, windshield wipers, and other safety equipment.

If you own a vehicle that is exempt from emissions testing but you live in a county that requires it, you still need to show proof of exemption when you renew your registration. The Secretary of State will note the exemption in your registration file. Bring your vehicle title or registration to prove the model year if you are unsure whether your vehicle is exempt.

Frequently Asked Questions

Can I test my vehicle before my registration expires?

Yes. You can test up to 120 days before your registration expires. The result will be valid for two years from the test date, so you can renew your registration when ready after passing.

What if I move out of a county that requires emissions testing?

If you move from Cook, DuPage, Kane, Lake, McHenry, or Will County to a county that does not require emissions testing, you no longer need to test. When you renew your registration at your new address, the Secretary of State will update your file and you will not be required to test again unless you move back to a testing county.

Do I need to test if I just bought a used car?

You need to test only when you renew your registration. If you bought a used car with a current registration, you can drive it until the registration expires. At renewal time, you must have a passing emissions test result if you live in a testing county.

What if the testing station says my vehicle cannot be tested?

Some vehicles — such as certain specialty or modified vehicles — may not be compatible with the OBD scanner. Contact the Illinois Environmental Protection Agency directly for guidance. You may be able to request a waiver or alternative test method, though this is rare.

Can I test at any time of year?

Yes. Testing stations are open year-round, though hours vary by location. Winter weather can sometimes cause delays, so plan ahead if you are testing near your registration expiration date.