Driver guide · Elgin Auto Sales & Service Center · Elgin, IL
Illinois Emissions Testing: Who Needs It and How It Works
Illinois requires vehicle emissions tests in the Chicago and Metro-East St. Louis areas, and a vehicle that is due must pass or otherwise comply before its license plates can be renewed. Here is which vehicles are tested, how often, how the OBD test works, why a lit check engine light with stored trouble codes means a fail, and what to do if a vehicle fails or you buy a used car.
4 yearsage when most gasoline vehicles are first tested (IEPA)
Every 2 yearstypically even model years in even years, odd in odd (IEPA)
Freeno charge for the required test (IEPA)
4 monthstest notice mailed up to this far before plates expire (IEPA)
The short answer
Most 1996 and newer gasoline cars and light trucks registered in the Chicago or Metro-East St. Louis testing areas need an emissions test once they are four years old, then every two years, in the month their plates expire. The test reads the on-board diagnostics (OBD) computer: a lit check engine light with stored trouble codes is a fail. Your Secretary of State renewal notice says whether a test is required.
Who needs an emissions test in Illinois
The federal Clean Air Act requires vehicle emissions inspection programs in large, urbanized areas that do not meet the national air quality standard for ozone, and the Illinois Vehicle Emissions Inspection Law of 2005 (625 ILCS 5/13C) sets up the program in Illinois. The Illinois EPA says air pollution levels in the Chicago and Metro-East St. Louis areas still exceed the ozone standard, so the program operates there.
Most 1996 and newer gasoline-powered passenger vehicles are subject to inspection after they are four years old. The inspection month matches the expiration of the vehicle's license plate, and typically even model-year vehicles are inspected in even years and odd model-year vehicles in odd years. The Illinois Air Team's example: a 2021 vehicle is tested for the first time in 2025. Testing also covers 2007 and newer heavy-duty vehicles with a gross vehicle weight rating between 8,501 and 14,000 pounds.
From the Illinois EPA Vehicle Emissions Testing page and the Illinois Air Team page Does My Vehicle Need to be Tested?, read November 3, 2026. This page is a summary, not legal advice.
Vehicles that are not emissions tested
The Illinois Air Team lists these vehicles as not subject to emissions testing:
Diesel and all-electric
Diesel-powered vehicles and vehicles powered exclusively by electricity. Hybrid-electric vehicles are still tested.
Motorcycles
Motorcycles, motor-driven cycles and motorized pedal-cycles.
Older and special vehicles
Antique and expanded-use antique vehicles, custom vehicles, street rods, and vehicles of model year 1967 or before.
Farm vehicles
Farm vehicles and implements of husbandry.
Heavier vehicles
Model year 2006 or earlier vehicles rated between 8,501 and 14,000 pounds GVWR, and any vehicle rated over 14,000 pounds.
Others
Vehicles not subject to registration, vehicles registered in and complying with another state's emissions program, vehicles with a Junking Certificate, and government implements of warfare.
From the Illinois Air Team, Does My Vehicle Need to be Tested? and Frequently Asked Questions, read November 3, 2026.
How the Illinois OBD emissions test works
For 1996 and newer passenger cars and light-duty trucks, including vans, SUVs and hybrids, Illinois uses an On-Board Diagnostics (OBD) test. A scan tool is connected to the vehicle's on-board computer to check the OBD system status (readiness checks), whether the Malfunction Indicator Lamp is commanded on, and any stored diagnostic trouble codes.
A vehicle fails if the lamp (the check engine light) is commanded on and trouble codes are present, or if the OBD system is inoperable or the connector is missing, damaged or inaccessible. The Air Team notes that if the lamp is on for a transmission code, it is emissions related.
Before you go, remove any device plugged into the OBD connector, such as an insurance dongle, GPS tracker or scan tool (vehicles with a BAIID connected there are tested without removing it). The test is free and needs no appointment. The registered owner does not have to bring the vehicle in; anyone can. All drivers must exit the driver's compartment during the test.
From the Illinois Air Team, About Vehicle Emissions Testing and Frequently Asked Questions, and the Illinois EPA vehicle emissions testing FAQ, read November 3, 2026.
If your vehicle fails or is rejected
What the Illinois Air Team says happens next:
You get a report
The inspector gives you a Vehicle Inspection Report with detailed results and a condensed Repair Shop Report listing repair facilities within 15 miles of the test site.
Repair, then retest
A vehicle that fails must be repaired and retested. The Air Team recommends a Recognized Repair Technician who is trained, experienced and equipped to repair emissions-related failures.
Repair Data Form
The inspector also gives you a Repair Data Form. The repair technician should complete and submit it online for you; if not, bring the completed form to the retest. Retests are rejected when the form is not submitted or completed.
Rejected is not failed
A vehicle can be rejected instead of failed, most often because its OBD monitors were not ready, the Repair Data Form was incomplete, or it was brought in too early. Rejects do not count as tests. Disconnecting the battery resets the monitors on most vehicles.
Waivers and extensions
A vehicle that has been tested at least twice, has been repaired and still fails may qualify for a Repair Waiver. If a vehicle failed and needs repairs the owner cannot afford, the owner may apply for a one-year Economic Hardship Extension.
From the Illinois Air Team, Frequently Asked Questions and Waivers, Exemptions & Extensions, read November 3, 2026.
Test notices and license plate renewal
A test notice is mailed up to four months before your license plates expire, and you can sign up for electronic test notifications. The Illinois EPA urges motorists to test several weeks before the plates expire, so there is time for repairs and a retest if needed.
Vehicles must pass an emissions test or otherwise comply with the Inspection Law before the registration can be renewed, and the Illinois Secretary of State's renewal notice states whether compliance is required. The Illinois Air Team also has a Vehicle Eligibility Check tool that tells you when your vehicle is due.
From the Illinois EPA Vehicle Emissions Testing page and FAQ, and the Illinois Air Team, About Vehicle Emissions Testing and Frequently Asked Questions, read November 3, 2026.
Moving, buying or selling a vehicle
If you move, update the address on your driver's license and vehicle registration with the Illinois Secretary of State. Once your record is updated, you only receive a test notice if your new address is inside the testing area. If you sell a vehicle, tell the Secretary of State you no longer own it so the test notices stop.
Buying a used car? The Illinois Air Team's Vehicle Eligibility Check tool tells you when a vehicle is due. A vehicle located and primarily used outside the testing area, in a state or county without emissions testing, may qualify for an Out of Area Exemption.
From the Illinois Air Team, Frequently Asked Questions and Out of Area Exemption, read November 3, 2026.
Check engine light on? Service at Elgin Auto Sales & Service Center
A lit check engine light with stored trouble codes means a failed test, so have it looked at before your test is due. Our service department works on new and pre-owned vehicles, including Toyota, GMC, Buick, Honda, Kia and Hyundai models, and our guide on what to do when the check engine light comes on explains the first steps.
Our service department at 1200 E. Chicago St. in Elgin is open Monday to Friday 8 a.m. to 5 p.m. and Saturday 8 a.m. to 4 p.m., and is closed Sunday. Schedule service, see our service specials or get directions.
Illinois emissions testing FAQ
Which vehicles need an emissions test in Illinois?
Most 1996 and newer gasoline-powered passenger vehicles are subject to testing after they are four years old, the Illinois EPA says. Even model-year vehicles are typically tested in even years and odd model-year vehicles in odd years, in the month the license plate registration expires.
Is emissions testing required everywhere in Illinois?
No. The Illinois EPA says the program covers the Chicago and Metro-East St. Louis areas. Your Illinois Secretary of State license plate renewal notice states whether emissions compliance is required.
Will my car fail if the check engine light is on?
Yes, if trouble codes are stored. The Illinois Air Team says a vehicle fails the OBD test if the Malfunction Indicator Lamp is commanded on and diagnostic trouble codes are present.
How much does an Illinois emissions test cost?
The required test is free, the Illinois EPA says, and no appointment is needed.
Are electric and diesel vehicles exempt?
Yes. Diesel-powered vehicles and vehicles powered exclusively by electricity are not subject to testing. Hybrid-electric vehicles are tested.
Can someone else take my car for the test?
Yes. The Illinois Air Team says the registered owner does not have to bring the vehicle in; anyone can.
What are your service hours?
Monday to Friday 8 a.m. to 5 p.m. and Saturday 8 a.m. to 4 p.m. We are closed Sunday.
Get ready for your test
Schedule service at 1200 E. Chicago St. in Elgin if your check engine light is on.
Sources
Emissions testing rules are from the Illinois EPA and the Illinois Air Team (the Illinois EPA's testing program website), read November 3, 2026. Rules change; this page is a plain-language summary, not legal advice. Service hours and address are from our own website, checked the same day.
- Vehicle Emissions Testing (program areas, eligibility, enforcement), Illinois EPA, read November 3, 2026
- Vehicle Emissions Test Program FAQ (free testing, no appointment, test notices), Illinois EPA, read November 3, 2026
- Does My Vehicle Need to be Tested? (eligibility, vehicles not tested), Illinois Air Team, read November 3, 2026
- About Vehicle Emissions Testing (OBD test, plate renewal), Illinois Air Team, read November 3, 2026
- Frequently Asked Questions (test, failing, rejections, moving), Illinois Air Team, read November 3, 2026
- Waivers, Exemptions & Extensions, Illinois Air Team, read November 3, 2026
- Out of Area Exemption, Illinois Air Team, read November 3, 2026
- Service department and service hours, Elgin Auto Sales & Service Center
- Home page: address and service hours, Elgin Auto Sales & Service Center