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Drivers living in the state of Illinois may need to complete emissions testing on their vehicles periodically. Most cars made after 1996 require emissions testing if they’re 4 or more years old and if the car owner lives in a certain county.[1] Some people and vehicles are exempt from these rules, but most drivers will need to comply with these testing requirements.

Here’s what you need to know about Illinois emissions testing requirements.

How does emissions testing work in Illinois?

While not all states require regular emissions or smog testing, Illinois state law does require it.[2] In 1990, the Clean Air Act required the Environmental Protection Agency (EPA) to set certain National Ambient Air Quality Standards (NAAQS) to help protect the environment and public health. The EPA advises emissions testing to help improve air quality.[3]

Because the air in certain parts of Illinois exceeds the ozone NAAQS, drivers in some areas of this state must comply with regular emissions testing. Due to the Illinois Vehicle Emissions Inspection Law of 2005, drivers living in a county or ZIP code with air pollution issues must complete emissions testing if their car is more than 4 years old and was built after 1996. This inspection typically occurs when the vehicle’s license plate expires.

What do emissions tests include?

During emissions tests in Illinois, most cars will undergo an on-board diagnostics (OBD) test, which involves using a scan tool to monitor a car’s on-board computer. This tool checks the OBD system status through a readiness check and identifies whether the malfunction indicator lamp/light is on. The scanning tool can also retrieve any stored diagnostic trouble codes.[4]

The car will likely pass the OBD test if the OBD system works.

Read More: Cheap Car Insurance in Illinois

Illinois emissions testing requirements

If an Illinois car qualifies for regular emissions testing, then the owner must complete an emissions test every two years once the car reaches 4 years old. If a car fails an emissions inspection, the owner will need to have it retested after completing any necessary repairs.

Counties that require emissions testing

Where you live in Illinois affects whether you’ll be required to undergo emissions testing for your car every two years.

You may have to undergo testing if you live in one of the following Illinois counties:

  • Cook

  • Dupage

  • Kane

  • Kendall

  • Lake

  • Madison

  • McHenry

  • Monroe

  • St. Clair

  • Will

If you live in Cook, Lake, or Dupage counties, you must take your car in for testing every two years. In specific ZIP codes in the other counties listed above, exclusions allow some drivers to forgo emissions testing. If you don’t know whether your vehicle needs to be tested, you can confirm your car’s status through the Office of the Illinois Secretary of State’s Title and Registration Status Inquiry.[5]

Learn More: Calculating How Much Car You Can Afford

Vehicles that must complete emissions testing

Certain vehicles must complete emissions testing if the car owner lives in an eligible area.[6] The vehicles include:

  • Light-duty vehicles, light-duty trucks, and heavy-duty vehicles at or below 14,000 pounds

  • Heavy-duty vehicles above 14,000 pounds

  • Heavy-duty vehicles at or below 14,000 pounds

  • Highway motorcycles

  • Off-highway motorcycles

  • All-terrain vehicles

The majority of gasoline-powered passenger vehicles built during 1996 or later typically require testing. You’ll receive a test notice if you need to complete emissions testing.

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Vehicles exempt from emissions testing

Vehicles exempt from emissions testing include the following:

  • Cars built in 1967 or before

  • Vehicles built in 1995 or before if compliant with the Illinois Vehicle Emissions Inspection Law as of Feb. 1, 2007

  • Diesel-powered vehicles

  • Electric vehicles (but not hybrids)

  • Motorcycles (motor-driven cycles and motorized pedal-cycles)

  • Street rods

  • Farm and husbandry vehicles

  • Antique vehicles

  • Custom vehicles

  • Vehicles with a junking certificate

  • Government-owned war vehicles

  • Parade and ceremonial-purpose vehicles operated on a not-for-profit basis by select groups

  • Vehicles operated only for amateur or professional sports activities

  • Vehicles registered in another state that remain compliant with that state’s emissions laws[7]

How to complete emissions testing in Illinois

Car owners will need to take the following steps to complete emissions testing in Illinois:

  • Prepare for an emissions test. To avoid failing an emissions test, first confirm that your check engine light is off and that the OBD system is operating. Also confirm that your car’s diagnostic link connector isn’t damaged, inaccessible, or missing before you take your vehicle to an Illinois vehicle emissions testing center.

  • Find a testing center. To find Illinois emissions test locations, use the Illinois Air Team Testing Station Locator.[8]

  • Complete the inspection. A fairly quick process, emissions testing usually only lasts between 15 and 40 minutes. Costs vary for this test, but you can expect it to cost around $20.

See Also: The 6 Critical Things to Do After Buying a Used Car

What to do if you fail emissions testing

If your car fails an emissions test, you need to repair the issue that caused the failure before retesting. After a failed test, you’ll receive the following documents to help you and a repair technician determine how to make the necessary repairs:

  • Vehicle inspection report and certificate

  • Required vehicle repair data

  • Repair shop report card

Illinois emissions testing FAQs

Find answers to some commonly asked questions about Illinois emissions testing below.

  • What do you do if you lose your emissions test notice?

    If you lose your emissions test notice, you can check the current status of your car’s testing requirements through the Illinois Title and Registration Status Inquiry.

  • Who is exempt from emissions testing in Illinois?

    Vehicles of a certain type, built before select years, or that belong to drivers in certain counties can be exempt from emissions testing in Illinois. Most gasoline-powered passenger vehicles of model year 1996 or newer in these counties must undergo emissions testing: Cook, Dupage, Kane, Kendall, Lake, Madison, McHenry, Monroe, St. Clair, and Will. But vehicles in certain ZIP codes may be exempt.

  • How do you prepare your vehicle for emissions testing in Illinois?

    To prepare your car to pass an emissions test in Illinois, check on a few vehicle elements first. Confirm that your check engine light is off, that the OBD system is operating, and that your car’s diagnostic link connector is present, undamaged, and accessible before you attend the test.

  • Does Illinois require emissions testing?

    The state of Illinois requires certain vehicles in select counties to undergo emissions testing to help improve air quality and public health. Not all states require emissions testing.

  • Can you pass a vehicle emissions test with a check engine light on?

    No, you can’t pass a vehicle emissions test with a check engine light on. Having this light on is one of the main reasons cars fail this test. Before you take your car to an Illinois emissions test facility, confirm the check engine light is off.

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  1. Illinois Environmental Protection Agency. "Vehicle Emissions Testing Program." Accessed February 3, 2023
  2. "Smog Check – Vehicle Emissions Tests." Accessed February 3, 2023
  3. United States Environmental Protection Agency. "NAAQS Table." Accessed February 3, 2023
  4. Illinois Air Team. " About Vehicle Emissions Testing." Accessed February 9, 2023
  5. Office of the Illinois Secretary of State. "Title and Registration Status Inquiry." Accessed February 3, 2023
  6. Illinois Air Team. " Does My Vehicle Need to be Tested?." Accessed February 9, 2023
  7. "Car Inspection in Illinois." Accessed February 3, 2023
  8. Illinois Air Team . " Testing Station Locator." Accessed February 3, 2023
Jacqueline DeMarco
Jacqueline DeMarco

During college, Jacqueline DeMarco interned at a retirement plan advisory firm and was tasked with creating a presentation on the importance of financial wellness. During her research into how money can affect our health, relationships and career, Jacqueline realized just how important financial education is. Jacqueline is a contributor for Insurify and has worked with more than a dozen financial brands, including LendingTree, Capital One, Credit Karma, Fundera, Chime, Bankrate, Student Loan Hero, ValuePenguin, SoFi, and Northwestern Mutual, providing thoughtful content to give readers insight into complex topics that they likely didn’t learn in school.