What Illinois emission testing requires and who has to do it
Illinois requires emission testing for most vehicles registered in the state, but the rules depend on where you live and how old your car is. The state divides the requirement into two zones: the Chicago metropolitan area (Cook, DuPage, Kane, Lake, McHenry, and Will counties) and the rest of Illinois. Vehicles in the Chicago area must pass an emission test every two years; vehicles outside that zone must test every three years.
Your car is exempt if it is a model year 1996 or older, a diesel vehicle, a motorcycle, or a vehicle that has been registered in Illinois for less than 30 days. Hybrid and electric vehicles are also exempt. If your vehicle falls into one of these categories, you do not need to test, but you will still need to renew your registration through the Secretary of State.
The emission test itself checks whether your vehicle's exhaust meets state pollution standards. A technician will connect a probe to your vehicle's diagnostic port (usually under the steering wheel) and run a computerized scan. The test takes about 10 to 15 minutes and costs around $30 to $35, though prices vary by testing station.
Key Takeaways
- Vehicles in the Chicago area must test every two years; all other Illinois vehicles must test every three years.
- Your vehicle's emission test status is checked when you renew your registration, and you cannot renew without a passing test result.
- You can find authorized testing stations through the Illinois Environmental Protection Agency website or by calling 1-800-253-5833.
- If your vehicle fails, you have 30 days to repair it and retest at no additional charge at the same station.
- Vehicles model year 1996 and older, motorcycles, hybrids, and electric vehicles are exempt from testing.
How to find an authorized testing station
Illinois does not run the emission tests itself. Instead, the state contracts with private testing stations, called Inspection and Maintenance (I/M) stations, to perform the tests. You can find a station near you by visiting the Illinois Environmental Protection Agency website and using their station locator tool, or by calling their hotline at 1-800-253-5833.
When you search for a station, you will see the address, phone number, and hours of operation. Many stations are gas stations, repair shops, or dedicated testing centers. You do not have to go to a dealership; any authorized I/M station will do. It is a good idea to call ahead to confirm they are open and to ask whether you need an appointment, since some stations accept walk-ins while others require you to book a time slot.
What happens when you take your vehicle to test
Bring your vehicle registration and a valid photo ID to the testing station. The technician will verify your vehicle information against the registration and then connect a diagnostic scanner to your vehicle's onboard computer. The scanner reads emissions data that your vehicle has already recorded; the technician does not need to drive your car.
The test checks whether your vehicle's emissions fall within the state limits for carbon monoxide, nitrogen oxides, and other pollutants. Most vehicles pass on the first attempt. If your vehicle passes, the technician will print a receipt and report the result to the Illinois Secretary of State electronically. You can then use that receipt when you renew your registration.
The entire process, from check-in to receipt, usually takes 15 to 30 minutes depending on how busy the station is.
What to do if your vehicle fails the emission test
If your vehicle fails, the technician will give you a written report showing which emissions standards your vehicle did not meet. The report will also list the diagnostic trouble codes that triggered the failure. You have 30 days from the test date to repair the vehicle and return to the same station for a retest at no additional charge.
Common reasons for failure include a faulty oxygen sensor, a malfunctioning catalytic converter, a loose or missing gas cap, or an engine that is running too rich (burning too much fuel). Some repairs are inexpensive—a gas cap costs $10 to $20—while others, like a catalytic converter replacement, can cost several hundred dollars. If you are unsure what is wrong, take the diagnostic trouble codes to a mechanic who can diagnose the specific problem.
If you repair the vehicle and retest within 30 days at the same station, there is no additional testing fee. If you do not retest within 30 days, you will have to pay the full testing fee again at a different station.
How emission test results connect to vehicle registration
When you renew your vehicle registration with the Illinois Secretary of State, the system automatically checks whether a passing emission test result is on file for your vehicle. If you are in the Chicago area and your last test was more than two years ago, or if you are outside the Chicago area and your last test was more than three years ago, the Secretary of State will not allow you to renew until you provide a new passing test result.
You can renew your registration online, by mail, or in person at a Secretary of State facility. If you renew online or by mail, you will need to have a passing test result already on file before you submit your renewal. The test result is reported electronically by the testing station, so there is no paperwork to mail in yourself.
If your registration expires before you have a passing test result, your vehicle is no longer legally registered and you cannot legally drive it. It is a good idea to schedule your emission test at least a few weeks before your registration expires.
Preparing your vehicle before the emission test
You do not need to do anything special to prepare your vehicle for an emission test, but a few straightforward steps can improve your chances of passing. Make sure your gas cap is tight and not cracked; a loose cap is one of the most common reasons for failure. If your check engine light is on, have a mechanic scan the codes before you test, because the test will likely fail if the light is illuminated.
Drive your vehicle normally for at least 100 miles before testing. The emission test reads data from your vehicle's onboard computer, and that computer needs a full driving cycle to gather accurate information. If you have just had work done on your engine or emissions system, wait a few days and drive normally before testing.
You do not need to have your vehicle serviced or inspected before testing. The test itself is not a safety inspection; it only measures emissions.
What happens if you move or buy a used vehicle
If you move to Illinois from another state, your vehicle must have a passing Illinois emission test before you can register it in Illinois. You have 30 days from the date you move to obtain the test. If you buy a used vehicle in Illinois, the previous owner's test result does not transfer to you; you will need your own test result to register the vehicle in your name.
If you move from the Chicago area to a county outside the Chicago area (or vice versa), your testing frequency changes. For example, if you move from Cook County to Champaign County, your testing requirement changes from every two years to every three years. Your new registration renewal date will reflect the new testing schedule.
Frequently Asked Questions
Can I test my vehicle before my registration expires?
Yes. You can test your vehicle up to 90 days before your registration expires. The test result will be valid for the full testing period (two or three years depending on your zone), so testing early does not shorten how long the result lasts.
What if I fail the test and cannot afford the repair right away?
You have 30 days to repair and retest at the same station with no additional fee. If you cannot complete the repair within 30 days, you will have to pay the full testing fee again. Some repair shops offer payment plans or financing for larger repairs; ask your mechanic about options.
Do I need an emission test if I only drive my vehicle occasionally?
Yes, if your vehicle is registered in Illinois and is not exempt, you must test according to the schedule for your zone, regardless of how often you drive. The only exception is if your vehicle is model year 1996 or older, a motorcycle, hybrid, or electric vehicle.
What if the testing station says my vehicle cannot be tested?
Some vehicles cannot be tested if they have serious mechanical problems, such as a non-functioning engine or transmission. In that case, the station will give you a written report explaining why. You will need to have the vehicle repaired and tested at a different station, and you will pay the full testing fee again.
How long does a passing emission test result stay valid?
A passing result is valid for two years if you live in the Chicago area or three years if you live elsewhere in Illinois. The result expires on the same date your vehicle registration expires, so you will need a new test when you renew your registration.