Illinois emissions testing is required for most gasoline-powered vehicles in counties located near big cities every two years. But some exceptions may apply, depending on your ZIP code.
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The Illinois Environmental Protection Agency requires emissions testing to help improve air quality and public health — especially in urban areas, like Chicago, where reducing air pollution from motor vehicles is a top priority. 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, including those that surround Chicago and border St. Louis.[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 emissions testing works 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.
During emissions tests in Illinois, most cars will undergo an on-board diagnostics (OBD) test, which involves using a scanning 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.
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Illinois emissions testing requirements
If an Illinois car manufactured after 1996 qualifies for regular emissions testing, 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. Cars that require emissions testing must complete testing to renew registration.
Counties that require emissions testing
Only people who live in counties near large cities, like Chicago and outside of St. Louis, are required by law to pass an emissions test. Illinois emissions testing is generally required every two years if you live in Cook, Lake, or Dupage counties. Exclusions may apply in other counties, depending on your ZIP code.
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
Failure to get an emissions test on time can result in fines ranging from $50 to $300 or more. If you’re not sure if your vehicle needs to be tested, confirm your vehicle’s status online using the state’s Vehicle Eligibility Check tool.
Vehicles that must complete emissions testing
The majority of gasoline-powered vehicles built during 1996 or later require testing if they’re 4 years or older. Here’s a closer look at the types of vehicles that typically need emissions tests:[5]
Passenger cars
Light-duty trucks, including SUVs and vans
Heavy-duty vehicles 2007 model year and newer with a gross vehicle weight rating (GVWR) between 8,501 and 14,000
Vehicles exempt from emissions testing
Not all types of vehicles require Illinois emissions testing. Vehicles exempt from emissions testing include the following:[6]
2006 and earlier vehicles with a GVWR between 8,501 and 14,000 pounds
Vehicles with a GVWR higher than 14,000 pounds
How to complete emissions testing in Illinois
You’ll 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. Warm your vehicle up by driving it for at least 15 minutes before arriving for your test.
Complete the inspection. Emissions testing usually lasts between 15 and 40 minutes. Costs vary for this test, but it typically costs around $20.
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What to do if you fail emissions testing
Your vehicle may fail inspection if certain emissions systems aren’t functioning properly or as a result of wear and tear that causes gasoline vapors or other pollutants to escape into the environment. Keeping up with regular maintenance, such as replacing your spark plugs, can help avoid issues that may cause emissions testing failure.
If your car fails an emissions test, you can still drive it, but 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:
Repair shop report (RSR) with a snapshot with a list of nearby repair facilities
Repair data form (RDF) to be completed by a repair technician
The Illinois EPA recommends having repairs made by an expert technician trained in emissions diagnosis and repair. And after having your car repaired, the repair tech must complete and submit the RDF, or you can bring it with you when you return to the inspection facility for a recheck.
In some cases, you may qualify for a repair waiver. Common reasons include failure to pass after at least two tests, completion of a minimum of $1,111 in emissions-related repairs, or when all emissions control devices appear to be functioning properly.
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.
Sarah Archambault enjoys helping people figure out how to manage their finances and credit. She covers auto financing, banking, credit cards, credit health, insurance, and personal loans. Her work has been featured on Credit Karma, Experian, LendingClub, Sound Dollar and USA Today Blueprint. She also writes for national insurers, banks and financial institutions like Aetna, MassMutual, Stripe, and UnitedHealthcare.
Sarah has been a contributor at Insurify since December 2022.
5+ years in insurance and personal finance content
Ashley is a seasoned personal finance editor who’s produced a variety of digital content, including insurance, credit cards, mortgages, and consumer lending products.
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