What Illinois emissions testing requires
Illinois requires emissions testing for most vehicles registered in Cook County and the collar counties (DuPage, Kane, Lake, McHenry, and Will). If you live outside those six counties, you do not need an emissions test. If you live in one of those counties, you must pass an emissions test every two years as part of your vehicle registration renewal.
The test measures your vehicle's tailpipe emissions — specifically nitrogen oxides, particulate matter, and hydrocarbons — to confirm it meets state pollution standards. You cannot renew your registration without a passing test result on file. The test itself takes about 10 minutes and costs between $15 and $30, depending on which testing facility you choose.
Vehicles model year 1996 and newer are subject to the test. Diesel vehicles, motorcycles, and vehicles registered as salvage or antique are exempt. If your vehicle fails, you have 30 days to repair it and retest at no additional charge.
Key Takeaways
- Emissions testing is required every two years only if you register your vehicle in Cook County or the five collar counties surrounding Chicago.
- You must have a passing test result before you can renew your vehicle registration with the Illinois Secretary of State.
- Any certified emissions testing facility in Illinois can perform the test; you do not have to use a specific location.
- If your vehicle fails, you have 30 days to make repairs and retest without paying the testing fee again.
- Vehicles older than 1996, motorcycles, and vehicles registered as antique or salvage do not require testing.
Finding a testing facility and scheduling
You can find certified emissions testing facilities through the Illinois Environmental Protection Agency website, which maintains a searchable list of all approved stations. The list includes the facility name, address, phone number, and hours. Most facilities are independent repair shops, quick-lube centers, or dedicated testing stations.
You do not need an appointment at most facilities — you can drive in during business hours and wait your turn. Some facilities do accept appointments, which can reduce your wait time. Call ahead if you want to confirm hours or ask whether they take walk-ins.
Bring your vehicle registration and a valid photo ID. The technician will connect a diagnostic device to your vehicle's onboard computer and run the test. You will receive a printed result when ready. If you pass, the result is automatically reported to the Secretary of State's office within one business day.
What happens if your vehicle fails the test
A failed test means your vehicle's emissions are above the state limit for at least one pollutant. The test result will specify which emissions failed. Common reasons for failure include a faulty oxygen sensor, a malfunctioning catalytic converter, or an engine problem that triggers the check engine light.
You have 30 days from the test date to repair your vehicle and retest. The retest is free — you do not pay the testing fee again within that 30-day window. You can take your vehicle to any repair shop you choose; you are not required to use the testing facility that performed the initial test.
If you do not retest within 30 days, you cannot renew your registration. If you repair the vehicle but want to retest after the 30-day period ends, you will pay the full testing fee again. If your vehicle continues to fail after repairs, consult a mechanic about more extensive diagnostics.
Timing your test with registration renewal
Your emissions test must be current when you renew your registration. Illinois allows you to test up to 120 days before your registration expires. This means you can test early in your renewal window without waiting until the last moment.
Your registration renewal notice from the Secretary of State will show your expiration date. Plan to test at least two weeks before that date to allow time for repairs if you fail. If you test and pass, the result is valid for two years from the test date, so you do not need to test again until your next renewal cycle.
If your registration has already expired, you cannot legally drive your vehicle. You must test and renew before you can register it again. Some facilities offer same-day testing, but you should not wait until your registration expires to schedule.
Vehicles that do not require testing
Motorcycles, mopeds, and vehicles registered as antique (generally 25 years or older) are exempt from emissions testing. Vehicles registered as salvage or rebuilt salvage are also exempt. Diesel-powered vehicles registered before 2007 are exempt, though newer diesel vehicles may be subject to testing depending on their registration type.
If you are unsure whether your vehicle is exempt, check your registration documents or call the Illinois Secretary of State's office. Some vehicles that appear to be exempt based on age or type may still be required to test if they are registered for regular road use in the six-county region.
What to do if you move or change counties
If you move from a county that requires testing to one that does not, you no longer need to test. If you move into Cook County or a collar county from outside the region, you will need to test before your next registration renewal. Your new registration will reflect the testing requirement based on your new address.
If you move within the six-county region, the testing requirement stays the same — you still test every two years. When you renew your registration after moving, update your address with the Secretary of State. Your emissions test result from before the move remains valid until it expires.
Understanding your test results
A passing result shows that your vehicle's emissions are at or below the state standard for all measured pollutants. The result includes specific numbers for nitrogen oxides, particulate matter, and hydrocarbons, along with your vehicle's identification number and the test date. You will receive a printed copy at the testing facility.
The testing facility reports the result electronically to the Secretary of State, so you do not need to submit anything yourself. You can renew your registration online, by mail, or in person once the result is on file. If you want to verify that your result was received, you can check your registration status through the Secretary of State's website.
Keep your printed test result for your records. If there is ever a question about whether you tested, you have proof of the date and facility. Some repair shops also keep records if you need to reference your testing history.
Frequently Asked Questions
Do I need an emissions test if I just bought a used car in Illinois?
If you register it in Cook County or a collar county, yes — you need a passing test before you can complete the registration. If the vehicle was previously registered in Illinois, the seller's test result does not transfer to you. You must obtain your own test result. If you are registering an out-of-state vehicle, you will need to test before registration.
Can I test my vehicle before my registration expires?
Yes. Illinois allows you to test up to 120 days before your registration expires. This gives you time to repair and retest if you fail, without rushing at the last minute. The test result is valid for two years from the test date.
What if I fail the test and cannot afford repairs right away?
You have 30 days to repair and retest at no additional testing cost. If you cannot repair within 30 days, your registration will expire and you cannot legally drive the vehicle. Some repair shops offer payment plans. Contact your local mechanic or the testing facility for options.
Does a check engine light mean I will fail the emissions test?
Not necessarily, but it increases the likelihood. A check engine light indicates a problem the vehicle's computer has detected, which often relates to emissions. The only way to know is to test. Many repair shops can read the code for free or low cost before you test.
Can I test in a different county than where I live?
Yes. You can test at any certified facility in Illinois, regardless of where you live. The result is reported to the Secretary of State based on your registration address, not the testing location. Some people test at a facility near their workplace for convenience.