What Illinois requires for emissions testing

Illinois requires an emissions test for most vehicles registered in Cook, DuPage, Kane, Lake, McHenry, and Will counties — the six-county Chicago metropolitan area. Vehicles in the rest of the state do not need one. The test measures tailpipe emissions to confirm your vehicle meets state air quality standards.

You must pass an emissions test before you can renew your vehicle registration in these counties. The test is separate from your safety inspection; you need both. Illinois does not perform the test itself — instead, the state licenses private testing stations to conduct the exam.

The test costs money (the fee varies by station but typically ranges from $15 to $30) and takes about 15 minutes. You cannot renew your registration online or by mail in the covered counties until you have a passing test result on file with the Secretary of State.

Key Takeaways

  • Illinois emissions testing is required only in Cook, DuPage, Kane, Lake, McHenry, and Will counties; vehicles outside these counties do not need one.
  • You must pass the test before renewing your vehicle registration — the Secretary of State will not process a renewal without a passing result.
  • Private licensed testing stations perform the test, not state offices, and you choose which station to visit.
  • The test takes about 15 minutes and costs between $15 and $30, depending on the station.
  • Vehicles older than 25 years and certain other categories are exempt from testing, though you still need a safety inspection.

Which vehicles must be tested in Illinois

Not every vehicle needs an emissions test in the covered counties. Gasoline-powered cars, SUVs, and light trucks registered in those six counties must be tested. Diesel vehicles, motorcycles, and vehicles registered outside the six-county area are exempt.

Vehicles manufactured more than 25 years ago are also exempt. A 2000 model year vehicle, for example, would not need an emissions test starting in 2025. Vehicles with a gross vehicle weight rating over 14,000 pounds are exempt as well.

New vehicles are exempt for the first four model years after purchase. A vehicle purchased new in 2024 does not need an emissions test until 2028. After that, it must be tested every two years when you renew your registration.

How to find a testing station and schedule

The Illinois Secretary of State maintains a searchable list of licensed emissions testing stations on its website. You can filter by county and city to find stations near you. The list includes the station's address, phone number, and hours of operation.

Most stations accept walk-ins, but some require appointments. Call ahead to confirm hours and whether you need to schedule. Bring your vehicle keys, proof of ownership (registration or title), and a valid photo ID.

Testing stations are typically open during standard business hours, though some offer evening or weekend appointments. If you cannot reach a station by phone, many now accept appointment requests through their websites or through the Secretary of State's online system.

What happens during the test

The technician will connect a probe to your vehicle's tailpipe and measure the levels of carbon monoxide, hydrocarbons, and nitrogen oxides in your exhaust. The vehicle's onboard diagnostic system is also checked to confirm no emissions-related warning lights are active.

The test takes about 15 minutes total. Your vehicle must be warmed up (driven for at least 5 to 10 minutes before arrival) for an accurate reading. The technician will tell you when ready whether you passed or failed.

If you pass, the station sends the result electronically to the Secretary of State's database. You do not receive a paper certificate; the state pulls your test result when you renew your registration. If you fail, the station provides a written report showing which emissions levels were out of range.

What to do if your vehicle fails the test

A failed test means your vehicle's emissions are above the state limit for one or more pollutants. Common causes include a faulty oxygen sensor, a malfunctioning catalytic converter, a loose gas cap, or an engine problem that triggers the check engine light.

You have the option to repair the vehicle and retest at any station. There is no fee for a retest if you return within 30 days of the original failure. After 30 days, you pay the full testing fee again. Keep the failure report — it helps a mechanic diagnose the problem.

If repairs are expensive and your vehicle is older, you may want to get a second opinion from a trusted mechanic before spending money. Some repairs (like replacing a catalytic converter) are costly, while others (like tightening a gas cap or clearing a diagnostic code) are inexpensive.

Timing and registration renewal important date

You can take the emissions test anytime during your registration period, but you must have a passing result before the Secretary of State will renew your registration. If your registration expires before you pass the test, you cannot legally drive the vehicle.

Plan to test at least two weeks before your registration expires. This gives you time to address a failure if needed. If you fail close to your expiration date, you may not have time to repair and retest before your registration lapses.

Once you pass, the result is valid for two years (or until your next registration renewal, whichever comes first). You do not need to test again until your next renewal cycle.

Emissions testing fees and what they cover

Testing stations set their own fees within state guidelines. Most charge between $15 and $30 per test. Some stations charge slightly more for certain vehicle types (such as vehicles with high mileage or older model years), though this is not required by the state.

The fee covers the emissions test itself and the electronic transmission of your passing result to the Secretary of State. It does not cover any repairs your vehicle may need if it fails. Retests within 30 days of a failure are typically free or discounted; confirm the retest policy when you call the station.

Payment methods vary by station. Most accept cash and credit cards. Some stations may require payment before the test; others collect after. Ask when you schedule or arrive.

Frequently Asked Questions

Can I renew my registration without an emissions test?

No, not in the six covered counties. The Secretary of State will not process a registration renewal without a passing emissions test result on file. If you live outside those counties, you do not need a test at all.

What if I just moved to Illinois from another state?

If you are registering a vehicle in one of the six covered counties for the first time, you must pass an emissions test before the Secretary of State will issue your Illinois registration. Bring your out-of-state title or registration, proof of residency, and a valid ID to the testing station.

Do I need both an emissions test and a safety inspection?

Yes. Illinois requires both tests for vehicle registration in the covered counties. They are separate exams performed at different times. Some stations offer both services, but you can use different stations if you prefer.

What if my vehicle has the check engine light on?

Your vehicle will fail the emissions test if the check engine light is illuminated. Have the diagnostic code read by a mechanic before testing. The problem may be straightforward (a loose gas cap) or more complex (a sensor or converter issue), but it must be resolved before you can pass.

How long does a passing test result stay valid?

A passing result is valid for two years or until your next registration renewal, whichever comes first. You do not need to test again until your registration renewal is due. If you sell the vehicle, the new owner must obtain their own test result.