What Illinois Emissions Testing Requires

Illinois requires emissions testing for most vehicles registered in Cook County and the collar counties (DuPage, Kane, Lake, McHenry, and Will). The state tests whether your vehicle's exhaust meets federal clean air standards. You must pass an emissions test before you can renew your vehicle registration, and you'll need to retest every two years.

The test itself takes about 10 minutes and costs around $30 to $35, though the exact fee varies by testing station. Your vehicle is placed on a dynamometer — a machine that measures what comes out of your tailpipe while the engine runs under controlled conditions. The machine checks for excessive emissions of nitrogen oxides, particulate matter, and other pollutants.

Not every vehicle in Illinois needs testing. Vehicles registered outside the five-county area are exempt. Diesel vehicles, motorcycles, and vehicles that are fewer than four model years old are also exempt. If your vehicle is registered in the testing area and is four years old or older, you'll need to pass before renewal.

Key Takeaways

  • Illinois emissions testing is required every two years for vehicles registered in Cook County and the surrounding collar counties if the vehicle is at least four model years old.
  • The test costs $30 to $35 and takes about 10 minutes at a licensed testing station, and you must pass before you can renew your registration.
  • You can find approved testing stations through the Illinois Environmental Protection Agency website or by calling your local Secretary of State office.
  • If your vehicle fails, you have 30 days to repair it and retest at no additional charge at the same station.
  • Vehicles registered outside the five-county testing area, diesel vehicles, and vehicles fewer than four model years old do not require testing.

Finding an Approved Testing Station

Illinois maintains a list of licensed emissions testing stations on the Illinois Environmental Protection Agency (IEPA) website. You can search by zip code or county to find stations near you. Most stations are independent repair shops, quick-lube facilities, or dealerships that have been certified to perform the test.

When you call ahead, confirm that the station is currently accepting vehicles for testing. Some stations have limited hours or may be temporarily closed. You'll also want to ask whether they can perform repairs on-site if your vehicle fails, since having repairs and retesting done at the same place saves time.

You do not need an appointment at most stations, but calling first can tell you how long the wait is. Bring your vehicle registration and a valid photo ID. Some stations may ask for your vehicle identification number (VIN) over the phone to pre-register you.

What Happens During the Test

When you arrive, the technician will verify your vehicle information and run a preliminary check to make sure your vehicle is safe to test — checking that your brakes work, your tires are properly inflated, and your check engine light is not on. If your check engine light is illuminated, the vehicle will fail the test when ready, and you'll need to have the problem diagnosed and repaired before retesting.

Your vehicle is then driven onto the dynamometer. For most vehicles, the test runs the engine through a series of acceleration and deceleration cycles that simulate normal driving. The machine measures the exhaust gases during this cycle. The entire process takes 10 to 15 minutes.

Once the test is complete, you'll receive a printed result. If you pass, the station will transmit your results to the Secretary of State's office electronically, and you can proceed with your registration renewal. If you fail, the technician will provide you with a detailed report showing which emissions exceeded the standard.

What to Do If Your Vehicle Fails

A failed test does not mean you cannot drive your vehicle — it means you cannot renew your registration until you pass. You have 30 days from the test date to repair your vehicle and retest. The retest is free if you return to the same station where you originally failed.

Common reasons for failure include a faulty oxygen sensor, a malfunctioning catalytic converter, a leak in the fuel system, or a problem with the engine control computer. A technician at the testing station or at any repair shop can diagnose the specific issue. Many repair shops can fix emissions-related problems, and some issues are inexpensive to correct.

If you repair your vehicle and retest within 30 days at the same station, you pay nothing for the second test. If you wait longer than 30 days or go to a different station, you'll pay the full testing fee again. Keep your failed test receipt so you can prove to the repair shop what was wrong.

Preparing Your Vehicle Before Testing

Before you schedule a test, make sure your vehicle is in reasonable working condition. Check that your check engine light is off — if it's on, have the problem diagnosed before you go. Make sure your tires are properly inflated to the pressure listed on the driver's door jamb, not the maximum pressure on the tire itself.

If your vehicle has been sitting unused for a long time, drive it for at least 20 minutes before testing to warm up the engine and clear out any stale fuel. Vehicles that have just been started or are running cold often fail because the emissions system hasn't reached its normal operating temperature.

If your vehicle is very old or has a history of emissions problems, consider having a pre-inspection at a repair shop before you go to the testing station. This costs extra but can save you from failing and having to return. Some stations offer this service for $10 to $15.

Timing Your Test Around Registration Renewal

Your emissions test must be passed before you can renew your vehicle registration. Illinois sends renewal notices about 30 days before your registration expires. You can take the emissions test anytime during the two-year registration period, but it makes sense to do it close to your renewal date so you don't have to worry about it earlier.

If your registration expires on June 30, you can test anytime from July 1 of the previous year through June 30 of the renewal year. Testing early gives you time to repair and retest if you fail. Testing too close to your expiration date leaves no buffer if something goes wrong.

Once you pass, the testing station sends your results to the Secretary of State electronically. You can then renew your registration online, by mail, or in person at a Secretary of State facility. You do not need to bring the test results with you — the state has them on file.

Special Situations and Exemptions

If you have a vehicle that is registered in the testing area but you believe it should be exempt, you can request an exemption through the Secretary of State. Diesel vehicles, vehicles with fewer than 6,000 miles on the odometer, and vehicles that are fewer than four model years old are automatically exempt. Vehicles registered to owners over 65 years old may may have access to for a one-time exemption, though this varies by county.

If you move out of the testing area, you no longer need to test in Illinois. If you move into the testing area, you'll need to test before your first registration renewal in that area. If you purchase a used vehicle that has already been tested for the current cycle, you do not need to test again until the next cycle begins.

If you have a vehicle with a temporary registration or a dealer plate, you are not subject to emissions testing requirements. Once you register the vehicle permanently in your name in the testing area, the requirement begins.

Frequently Asked Questions

Can I test my vehicle before my registration expires?

Yes. You can test anytime during your two-year registration period. Testing early is actually a good idea because it gives you time to repair and retest if you fail. Just make sure the test is done within two years of your previous passing test, or it will expire before your registration does.

What if I fail the test and can't afford to repair my vehicle right away?

You have 30 days to repair and retest at no additional charge. If you cannot repair it within 30 days, you'll need to pay the testing fee again when you retest. You cannot renew your registration until you pass, so if your registration expires before you repair the vehicle, you'll be driving with an expired registration, which is illegal.

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

Only if your vehicle is registered in the testing area and is at least four model years old. If the previous owner already passed the test for the current cycle, you do not need to test again until the next cycle. The testing requirement follows the vehicle, not the owner.

What happens if I move out of the testing area?

Once your vehicle is registered outside the five-county area, you no longer need emissions testing. You can register your vehicle in the new county without a passing test. If you move back into the testing area later, you'll need to pass a test before your next registration renewal.

Can I test my vehicle at any repair shop, or does it have to be a licensed station?

It must be a licensed Illinois emissions testing station. Only stations certified by the IEPA can perform the official test. You can find the complete list on the IEPA website. Testing at an unlicensed shop will not count toward your registration renewal requirement.