Illinois requires emissions testing for most vehicles, and the rules depend on where you live and what you drive

Illinois divides the state into two emissions zones: the Chicago area (Cook, DuPage, Kane, Lake, McHenry, and Will counties) and the rest of the state. The Chicago area has stricter requirements because it does not meet federal air quality standards. If you live in the Chicago area, you must test every two years. If you live elsewhere in Illinois, you do not need emissions testing at all — your vehicle only needs a safety inspection.

Vehicles registered in the Chicago area must pass an On-Board Diagnostic (OBD) test, which reads your vehicle's computer to check emissions systems. The test takes about 10 minutes and costs around $15 to $20, though prices vary by testing station. Diesel vehicles, motorcycles, and vehicles model year 2025 and newer are exempt. Vehicles model year 1996 and older use a different test called a Two-Speed Idle test, which is less common and may cost more.

You can renew your vehicle registration without a passing emissions test, but you cannot legally drive on public roads without one. If you fail, you have 30 days to repair your vehicle and retest at no additional charge at the same station.

Key Takeaways

  • Only vehicles registered in Cook, DuPage, Kane, Lake, McHenry, or Will counties need emissions testing; the rest of Illinois requires only a safety inspection.
  • Chicago-area vehicles must test every two years using an OBD test that reads your vehicle's computer, costing $15 to $20 per test.
  • You can find approved testing stations through the Illinois Environmental Protection Agency website or by searching for "emissions testing near me" with your ZIP code.
  • If you fail, you have 30 days to fix the problem and retest free of charge at the same station.
  • Vehicles model year 1996 and older use a different test procedure and may have different exemptions.

Where to get tested in the Chicago area

The Illinois Environmental Protection Agency maintains a searchable list of approved testing stations on its website. You can filter by county and see each station's hours and contact information. Most stations are independent repair shops, quick-lube facilities, or dealerships. You do not need an appointment at most locations, though calling ahead can save you a wait.

Testing stations must follow state procedures and cannot charge more than the state-set maximum fee. If a station quotes you significantly more than $20, ask whether that price includes additional services like a diagnostic scan or repair work — those cost extra and are separate from the emissions test itself.

What happens if you fail the test

A failed test means your vehicle's emissions systems are not working correctly. Common reasons include a faulty oxygen sensor, a loose gas cap, a problem with the catalytic converter, or an engine misfire. The testing station will give you a report listing the specific code that triggered the failure.

You have 30 days from the test date to repair your vehicle and return to any approved station for a free retest. You do not have to return to the same station, though many people do because the technician is already familiar with the vehicle. If you retest within 30 days and pass, your emissions record is updated when ready. If you do not retest within 30 days, your vehicle remains in failed status and you cannot legally drive it on public roads.

If the repair is expensive and you are considering selling the vehicle, you can transfer the registration to a new owner. The new owner will inherit the failed test status and must repair and retest before they can register it in their name.

Timing your test around registration renewal

Your emissions test must be current when you renew your vehicle registration. Illinois allows you to test up to 60 days before your registration expires, so you can get ahead of the important date. If your registration expires on June 30, you can test as early as May 1.

You do not need to renew registration and test on the same day. Many people test several weeks early to avoid a last-minute rush if they fail. When you renew your registration online or at a Secretary of State facility, the system checks whether a passing test is on file. If it is not, the renewal will be blocked and you will be directed to test first.

Special cases: older vehicles, temporary registration, and out-of-state moves

Vehicles model year 1996 and older use a Two-Speed Idle test instead of OBD. This test revs the engine to specific speeds and measures tailpipe emissions directly. Fewer stations perform this test, so call ahead to confirm availability. The cost is typically higher than an OBD test, sometimes $30 to $40.

If you buy a used vehicle in Illinois and it has a failed emissions test on record, you must repair and retest it before you can register it in your name. If you buy a vehicle out of state and move it to the Chicago area, you must test it within 30 days of registering it in Illinois, even if it passed testing in another state.

Temporary registration permits do not exempt you from testing. If you are driving on a temporary permit in the Chicago area, you still need a passing emissions test before you can get permanent plates.

What the test does and does not check

The OBD test reads your vehicle's onboard computer to see whether emissions systems are functioning. It checks the catalytic converter, oxygen sensors, fuel system, and engine controls. The test does not measure actual tailpipe emissions — it only confirms that your vehicle's computer is not detecting a problem.

The test does not check your brakes, tires, lights, or any other safety systems. That is the job of the separate safety inspection required statewide. You may need both tests to renew your registration, depending on your county.

Frequently Asked Questions

Do I need emissions testing if I just moved to Illinois from another state?

If you moved to the Chicago area, yes — you must test within 30 days of registering your vehicle in Illinois. If you moved to a county outside the Chicago area, no — only safety inspection is required. Check which county you are registering in to be sure.

What if I fail the test and the repair costs more than the car is worth?

You can sell the vehicle to someone else, who will then be responsible for the repair and retest. You can also donate it to a charity, which typically handles the emissions issue. You cannot legally drive it on public roads until it passes, but you can keep it parked on private property indefinitely.

Can I test my vehicle before my registration expires, or do I have to wait until it is about to expire?

You can test up to 60 days before your registration expires. Many people test early to avoid a last-minute problem if they fail. The test date does not have to match your registration renewal date.

What if the testing station says my vehicle cannot be tested because it is too old or too new?

Vehicles model year 1996 and older need a Two-Speed Idle test, not an OBD test — call a different station that performs that test. Vehicles model year 2025 and newer are exempt from testing. If your vehicle falls into either category, confirm the exemption with the Illinois EPA before paying for a test you do not need.

Do I need to bring anything with me to the testing station?

Bring your vehicle registration or proof of ownership and a valid ID. The testing station will look up your vehicle in the state system using your license plate. Some stations may ask for your VIN as well, so having your registration handy makes the process faster.