About Vehicle Emissions Testing

What Vehicle Emissions Tests are Performed in Illinois?

An On-Board Diagnostics (OBD) test is used for most 1996 and newer passenger cars and light-duty trucks, including vans and sport utility vehicles, and 2007 and newer heavy-duty vehicles with a gross vehicle weight rating (GVWR) between 8,501 and 14,000 pounds.

How is the OBD test performed?

The OBD test consists of connecting a scan tool to a vehicle's on-board computer to determine the OBD system status (readiness checks) and whether the Malfunction Indicator Lamp/Light (MIL) is commanded on (in which case it would be illuminated), and to retrieve any stored diagnostic trouble codes (DTCs).

Vehicles will pass the OBD test if the OBD system is working, all required emissions system readiness checks have been completed and the MIL is not commanded on.

Vehicles will fail the OBD test if the MIL is commanded to be illuminated and DTCs are present. Vehicles will also fail if the OBD system is inoperable or if the OBD connector is missing, damaged or inaccessible.

For further information, refer to the “Understanding On-Board Diagnostics (OBD)” on the frequently asked questions page.

Vehicle Registration and Tag Renewal

License Plate Renewal-Based Enforcement of the Vehicle Emissions Testing Program

Vehicles must pass an emissions test or otherwise comply with the Illinois Vehicle Emissions Inspection Law of 2005 (625 ILCS 5/13C) (“Inspection Law”) before the vehicle’s registration (license plates) can be renewed. A Test Notice is mailed up to four (4) months prior to your vehicle’s license plate expiration to remind you to take your vehicle in for an emissions test.

The Secretary of State’s Office mails License Plate Renewal Notices that include a statement as to whether compliance with the Vehicle Emissions Inspection Law is required before a vehicle’s registration can be renewed. The Secretary of State’s Office sends paperless License Plate Renewal Notices via email to individuals who register at https://www.ilsos.gov/greenmail. Electronic notices do include a statement as to whether compliance with the Vehicle Emissions Inspection Law is required before a vehicle's registration can be renewed. 

To determine if your vehicle is eligible for an emissions test this year, use this Vehicle Eligibility Check tool. 

* Remember, you must have your vehicle tested before you can renew your registration.

Save Time! Renew Your Registration at a High Capacity Drive-Thru Testing Station!

Illinois motorists now have the option to renew their registration tags after their vehicle successfully passes an emissions test at a testing station. When it does, you will receive a passing emissions inspection certificate.

To renew, take the certificate to the testing station office before you leave the facility. No SOS renewal notice is needed to renew. Additional fees apply. Acceptable forms of payment include: Visa, MasterCard, Discover and American Express. No cash is accepted.