What Illinois requires for vehicle emissions

Illinois requires emissions testing for most vehicles registered in the state, but the rules depend on where you live and what you drive. If you live in the Chicago metropolitan area — Cook, DuPage, Kane, Lake, McHenry, or Will County — your vehicle must pass an emissions test every two years. If you live elsewhere in Illinois, you do not need emissions testing at all.

The test itself checks whether your vehicle's exhaust meets state pollution standards. A technician will plug a scanner into your vehicle's onboard diagnostic port, run the engine through a series of conditions, and measure what comes out. The whole process usually takes 10 to 15 minutes.

Vehicles that are model year 1996 and newer must pass the test. Vehicles older than 1996 are exempt. Diesel vehicles, motorcycles, and vehicles registered as antiques or classics also do not need to test.

Key Takeaways

  • Only vehicles registered in Cook, DuPage, Kane, Lake, McHenry, or Will County need emissions testing; the rest of Illinois has no requirement.
  • Testing is required every two years, and you can test any time during your two-year window — there is no specific month you must go.
  • You can find a testing station through the Illinois Environmental Protection Agency website or by calling 1-877-EPA-CARS.
  • A test costs between $20 and $30 and takes about 15 minutes; if you fail, you have 30 days to fix your vehicle and retest at no additional cost.
  • Your vehicle's registration will not renew if your emissions test is overdue or if you failed and did not retest within the grace period.

When your vehicle needs to be tested

Your emissions test is due every two years from the date you last passed. Illinois does not assign you a specific month — you can test anytime during your two-year window. Many people test when they renew their registration to keep everything on the same schedule, but you do not have to.

If your registration is about to expire and you have not tested yet, you must test before you can renew. The Secretary of State's office will not issue a new registration sticker until your emissions record is clear. If you are past due, you can still test, but your vehicle is technically not legal to drive on public roads until the test is complete and passes.

If you fail the test, you have 30 days to repair your vehicle and return for a retest. The retest is free — you only pay once. If you do not retest within 30 days, your registration will not renew.

Where to get tested in Illinois

Testing stations are run by private businesses under contract with the Illinois Environmental Protection Agency. You can find a station near you by visiting the IEPA's emissions testing website or by calling 1-877-EPA-CARS. The phone line can tell you which stations are open, their hours, and whether they have same-day appointments available.

Stations are spread across the six-county region, so you should have several options within a reasonable distance. Some stations are busier than others — if you call ahead, you can ask about wait times and book an appointment if they offer them.

Bring your vehicle's registration and proof of insurance. Some stations may ask for your driver's license as well. You do not need to bring any paperwork about previous tests.

What happens if you fail the emissions test

If your vehicle fails, the test report will tell you which emissions systems are not working correctly. Common failures include problems with the oxygen sensor, catalytic converter, or the vehicle's computer system. The report will not tell you how to fix it, but it will give you the specific codes that a mechanic can use to diagnose the problem.

You have 30 days to repair your vehicle and return for a retest. You can go to any mechanic you choose — you do not have to use a specific shop. Once you have made repairs, you can retest at any station in the region, not necessarily the one where you failed.

If you retest within 30 days and pass, your registration can renew normally. If you do not retest within 30 days, your registration will expire and you will need to renew it in person at a Secretary of State office, which takes longer and may involve additional fees.

Cost and what to expect during the test

A test costs between $20 and $30, depending on the station. This is a one-time fee per test — if you pass, you are done. If you fail and need a retest, the retest is free within the 30-day window.

During the test, a technician will ask you to turn on your vehicle and let it idle while they plug a scanner into the diagnostic port under your steering wheel. The scanner reads data from your vehicle's computer. You will sit in the vehicle while this happens. The technician may also ask you to rev the engine slightly or drive the vehicle onto a dynamometer, which is a machine that simulates driving conditions. The whole process takes 10 to 15 minutes.

You will receive a printed report when ready after the test. If you pass, the report shows that your vehicle met the standards. If you fail, the report lists the specific emissions codes that indicate what is wrong. Keep this report — you will need it if you take your vehicle to a mechanic, and you will need to bring it back when you retest.

Vehicles exempt from testing

Not all vehicles in Illinois need to test. Vehicles model year 1995 and older are exempt because they do not have the onboard diagnostic systems that the test requires. Diesel vehicles are exempt, as are motorcycles and mopeds. Vehicles registered as antiques or classics are also exempt, though you must have the correct registration designation.

If you own a vehicle that is exempt, you do not need to do anything — your registration will renew without an emissions test. If you are unsure whether your vehicle is exempt, you can call the IEPA at 1-877-EPA-CARS and describe your vehicle, and they can tell you whether testing is required.

Frequently Asked Questions

What if I move out of the testing counties after I pass my test?

Your test is valid for two years from the date you passed, regardless of where you live. If you move to a county that does not require testing, you do not need to test again. If you move back into a testing county, your two-year window continues from your last test date.

Can I test early, before my two years are up?

Yes. You can test anytime, and your new two-year window starts from the date you pass. Some people test early if they are planning to sell their vehicle or if they want to get testing done before a busy season at the stations.

What if my vehicle has a check engine light on?

A check engine light does not automatically mean you will fail. The test measures actual emissions output, not warning lights. However, the problem causing the light may also cause an emissions failure. You can test with the light on, but if you fail, you will need to fix the underlying problem before retesting.

Do I need an appointment, or can I just show up?

It depends on the station. Some stations take walk-ins, while others require appointments. Call ahead or check the station's website to find out. During busy times, wait times can be an hour or more if you do not have an appointment.

What if I fail and cannot afford to fix my vehicle right away?

You have 30 days to retest. If you cannot afford repairs when ready, you can wait — just make sure you retest before the 30 days are up. If you miss the important date, your registration will expire and you will need to renew it in person, which is more complicated. Some nonprofits and community programs offer low-cost vehicle repairs; the IEPA website has a list of resources by county.