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 these areas, you do not need to test. The state tests whether your vehicle's exhaust meets federal pollution standards — specifically, it measures hydrocarbons, carbon monoxide, and nitrogen oxides.

You must pass an emissions test before you can renew your vehicle registration. The test happens at an Illinois EPA emissions testing station, not at a regular mechanic or oil change shop. The state contracts with private testing facilities to run these stations, so locations vary by county.

The test itself takes about 10 to 15 minutes. A technician plugs a diagnostic scanner into your vehicle's onboard computer port (usually under the steering wheel) and runs a short test cycle. Your vehicle either passes or fails based on what the scanner reads.

Key Takeaways

  • Emissions testing is required only in Cook County and the five collar counties; all other Illinois counties do not require it.
  • You must test at an official Illinois EPA emissions testing station before you can renew your vehicle registration.
  • The test measures your vehicle's exhaust pollution levels and takes 10 to 15 minutes.
  • If your vehicle fails, you have 30 days to fix the problem and retest at no additional charge.
  • You can find testing stations and schedule appointments through the Illinois EPA website or by calling your county's testing program.

Finding a testing station in your county

The Illinois EPA maintains a list of testing stations by county on its website. You can search by your zip code or county name to see which stations are open and their hours. Most stations operate Monday through Friday during business hours, with some offering Saturday appointments.

You do not need to schedule an appointment at most stations — you can walk in during operating hours. However, some stations accept appointments online or by phone, which can reduce your wait time. Call ahead if you want to confirm a station is open or ask about current wait times.

Testing stations are typically located at automotive service centers, tire shops, or dedicated emissions testing facilities. Bring your vehicle registration and a valid ID. The cost varies slightly by station but is usually between $25 and $35.

What happens if your vehicle fails the test

If your vehicle fails, the testing station gives you a printed report showing which emissions standards your vehicle did not meet. This report tells you what type of repair your vehicle likely needs — for example, a faulty oxygen sensor, a problem with the catalytic converter, or an issue with the fuel system.

You have 30 days from the test date to have the vehicle repaired and retested. The retest is free if you return to the same station. You do not need to bring any repair receipts or proof of work; the technician straightforward runs the test again to see if the vehicle now passes.

If you cannot afford repairs when ready, you can still renew your registration by obtaining a waiver. A waiver allows you to register your vehicle for one year even though it failed the test, but you must retest the following year. Waivers are available if you have owned the vehicle for less than two years or if the cost of repairs exceeds a certain threshold (usually around $500 to $700, depending on the year). Ask the testing station about waiver options if you need one.

Timing your test with registration renewal

Your vehicle's emissions test is valid for two years from the test date. You can test any time during your registration renewal period, which is typically the month shown on your current registration sticker. Testing early gives you time to fix any problems before your registration expires.

If you test and pass, you can renew your registration when ready online, by mail, or in person at a Secretary of State office. You do not need to bring the test results — the testing station reports the results directly to the state.

If you test and fail, you have until your registration expires to either fix the vehicle and retest or obtain a waiver. Do not wait until the last day of your registration period to test, because you may not have time to schedule a retest if you fail.

Special cases: new vehicles, older vehicles, and electric cars

New vehicles (typically those less than four model years old) are exempt from emissions testing for their first few years of registration. Check the Illinois EPA website or call your county's testing program to confirm whether your vehicle is exempt based on its model year.

Very old vehicles (usually 1975 and earlier) may also be exempt. Vehicles registered as antiques or classics have different testing rules; contact your county program for details.

Electric vehicles and plug-in hybrids do not require emissions testing in Illinois because they produce zero tailpipe emissions. If you own an electric vehicle, you can renew your registration without testing.

What to do before you test

Before you go to a testing station, make sure your vehicle's check engine light is off. If the light is on, the vehicle will automatically fail the test. You can have a mechanic scan your vehicle's computer for free or low cost at many auto parts stores to see if there are any stored error codes.

Fill your gas tank at least three-quarters full before testing. Some testing procedures require adequate fuel pressure, and a nearly empty tank can cause a test failure.

Make sure your vehicle's battery is in good condition and fully charged. A weak battery can prevent the onboard computer from communicating properly with the testing scanner.

Frequently Asked Questions

Do I need emissions testing if I live in Illinois but outside Cook County and the collar counties?

No. Emissions testing is required only in Cook County (Chicago area) and the five collar counties: DuPage, Kane, Lake, McHenry, and Will. If you live anywhere else in Illinois, you do not need to test to renew your registration.

What if I just moved to Illinois from another state?

When you register your vehicle in Illinois for the first time, you must follow the emissions testing rules for your county. If you move into a testing county, you will need to test before your next registration renewal. If you move out of a testing county, you no longer need to test.

Can I test my vehicle before my registration renewal period?

Yes. You can test any time, and the results are valid for two years. Testing early is actually a good idea because it gives you time to fix any problems before your registration expires.

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

Some vehicles cannot be tested if they are not in safe operating condition — for example, if the check engine light is on, the vehicle will not communicate with the scanner, or if there is a visible safety problem. The testing station will tell you what needs to be fixed before testing can proceed. You may need to have a mechanic diagnose the problem first.

How long does it take to get my test results?

You receive your results when ready after the test. The testing station prints a report on the spot showing whether you passed or failed. The results are also reported electronically to the state, so you can renew your registration right away if you passed.