What Illinois requires for emission testing

Illinois requires emission testing for most vehicles registered in Cook County and the collar counties (DuPage, Kane, Lake, McHenry, and Will). If you live in these counties and your vehicle is model year 1996 or newer, you will need to pass an emissions test every two years as part of your vehicle registration renewal. Vehicles registered outside these counties do not need emissions testing.

The test measures what comes out of your tailpipe — specifically nitrogen oxides, particulate matter, and hydrocarbons. A machine plugs into your vehicle's onboard diagnostic port and reads whether your emissions are within the limits set by the Illinois Environmental Protection Agency (IEPA). The test takes about 10 to 15 minutes and costs around $30 to $35, though the exact price varies by testing station.

You can get tested at any station licensed by the IEPA. The state maintains a searchable list of testing locations on the IEPA website, organized by county. You do not have to go to a dealership — independent repair shops, quick-lube facilities, and dedicated emissions testing centers all perform the test.

Key Takeaways

  • Emission testing is required every two years in Cook County and the five collar counties for vehicles model year 1996 and newer.
  • You can be tested at any IEPA-licensed station, which you can find through the state's online location tool.
  • A failed test means your vehicle has an emissions problem that usually requires repair before you can register it.
  • If your vehicle fails, you have 30 days to repair it and retest for free at the same station.
  • Vehicles that fail twice in a row must go to a certified repair facility, not just any shop.

When your vehicle passes the test

A passing test means your vehicle's emissions are within legal limits. The testing station prints a receipt with a pass certificate, which you will need when you renew your vehicle registration. You can take this receipt to your local Secretary of State office or renew online if you have the certificate number from the receipt.

A passing test is valid for two years from the date you took it. You do not need to test again until your registration is up for renewal. If your registration expires before you get tested, you cannot legally drive the vehicle — so plan to test before your registration renewal important date.

What happens if your vehicle fails

A failed test means your vehicle's emissions exceed the legal limit in one or more categories. The testing station will give you a detailed report showing which emissions were too high. Common reasons for failure include a faulty oxygen sensor, a malfunctioning catalytic converter, or a check engine light that is on.

You have 30 days from the test date to repair the problem and return to the same testing station for a free retest. You do not pay for the second test. If you pass the retest within 30 days, you get your pass certificate and can register your vehicle. If you do not retest within 30 days, the 30-day window closes and you will have to pay for a new test.

If your vehicle fails a second time at the same station, you must take it to a certified repair facility — a shop that has been approved by the IEPA to diagnose and fix emissions problems. These shops have special training and equipment. The IEPA maintains a list of certified facilities by county on its website. You will pay for the repair and the retest at the certified facility.

How to find a testing station and schedule

The IEPA website has a searchable map of all licensed testing stations. You can filter by county and see the station's address, phone number, and hours. Most stations accept walk-ins, but some require an appointment — calling ahead is the safest approach.

Bring your vehicle keys, your vehicle registration, and a valid photo ID. The station will run the test and give you a receipt on the spot. If you pass, keep the receipt until you renew your registration. If you fail, the receipt will show your 30-day retest window and the station's contact information for scheduling your free retest.

What to do if you cannot pass after two attempts

If your vehicle fails twice, the IEPA's Repair information Program may help cover the cost of repairs at a certified facility. This program is designed for vehicles that fail emissions testing and need significant repairs to pass. You must meet income requirements, and the program covers a portion of the repair cost, not all of it.

To learn whether you may be may be able to access, contact the IEPA directly at 1-877-782-9942 or visit the IEPA website. They can tell you what documents you will need and which certified repair facilities participate in the program in your county. The program does not cover all repairs — it focuses on emissions-related problems like catalytic converters and oxygen sensors.

Emission testing and vehicle registration timing

Your emission test must be completed before you renew your vehicle registration. If your registration expires on June 15, you should test by early June to leave time for a retest if you fail. You cannot register your vehicle without a passing test certificate.

When you renew your registration online or at a Secretary of State office, you will need to provide the certificate number from your passing test receipt. If you renew online, the system will ask for this number. If you renew in person, bring the receipt with you. Registration renewal typically takes a few days to a few weeks, depending on whether you do it online or in person.

Vehicles exempt from emission testing

Vehicles registered outside Cook County and the collar counties do not need emission testing, even if they are driven in those counties occasionally. Vehicles model year 1995 and older are also exempt. Diesel vehicles and vehicles registered as classic or antique cars have different rules — contact the IEPA to confirm whether your vehicle is exempt.

If you move from an exempt county to Cook County or a collar county, you will need to get an emissions test before you can renew your registration in the new county. Plan for this when you move.

Frequently Asked Questions

Can I test my vehicle before my registration expires?

Yes. You can test up to 90 days before your registration expires. The test certificate is valid for two years, so if you test early, you will have a passing certificate ready when renewal time comes. This is a good strategy if you are worried about failing and needing time for repairs.

What if I fail the test and cannot afford to fix my vehicle?

Contact the IEPA Repair information Program at 1-877-782-9942 to see whether you may be may be able to access for help with repair costs. The program has income limits and does not cover all repairs, but it can help with emissions-specific problems. You can also get a second opinion from a certified repair facility about what actually needs to be fixed.

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

Only if your registration is coming due soon. A used car you just bought will have its own registration expiration date. You need to test before that date expires. If you just bought the car and the registration does not expire for another year, you have time before you need to test.

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

This can happen if your vehicle has a serious mechanical problem, like a broken transmission or no engine power. The station will give you a report explaining why. You will need to get the vehicle repaired at a regular repair shop first, then return to the testing station to try again. You may have to pay for a new test if you come back after 30 days.

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

Yes. You can test at any IEPA-licensed station in Illinois, regardless of which county you live in. The certificate is valid statewide. Some people test at a station near their workplace if that is more convenient than testing near home.