Emissions Testing in Wisconsin

Who Needs an Emissions Test or Smog Check

Vehicles that may require testing include autos or light trucks kept in seven southeastern Wisconsin counties, depending on model year and weight. Generally, model years 1996 to 2006 under 8,501 lbs (gasoline, natural gas, or hybrid), and 2007 and newer under 14,000 lbs (diesel, gasoline, natural gas, or hybrid) are subject to testing. Requirements vary by vehicle age, fuel type and location. Always confirm with the DMV for current applicability.

How Often Tests Are Required

Testing is generally required every other year at registration renewal, and also when a vehicle is registered due to change of ownership or new registration. There is often a 45‑day requirement to test following purchase, title change or moving into Wisconsin. These requirements align with biennial renewals or ownership transfers.

Where Emissions Testing Is Required

Emissions testing is required only in certain southeastern counties of Wisconsin that monitor air quality, not statewide. Locations such as in the greater Milwaukee region require testing, while other areas are exempt. Requirements vary by county based on air quality mandates and federal guidelines.

What Happens During the Test

During the emissions test, a technician connects to the vehicle’s OBD‑II port and performs a diagnostic scan. They check that the check‑engine light works, ensure system communication, and download emissions‑related data. The vehicle may undergo visual inspection of emissions controls. If the system is incomplete or diagnostic monitors are not ready, the vehicle may fail. The technician issues a printed report. If the vehicle passes, registration can proceed; if not, repairs and retesting are required.

Areas in Wisconsin That Require Emissions Testing

Requirements differ across the state depending on air‑quality priorities and population density. Emissions testing locations in Wisconsin focus on southeastern counties where pollution levels and federal standards necessitate monitoring. In larger cities such as Madison, Milwaukee, Waukesha, Racine, La Crosse and others, testing options may be available if they fall within designated counties. Areas with higher vehicle usage and denser populations often enforce stricter requirements and offer more test centers. Counties outside the designated zones generally do not require testing. Always check whether your area, including nearby cities, is subject to emissions testing before seeking a facility.

How the Emissions Test Works in Wisconsin

The testing process typically takes about 15 to 30 minutes. You should bring your registration renewal notice, vehicle title or emissions notice as proof of requirement. First, you drive into the test lane, present documents, and the inspector verifies your VIN and vehicle details. They then power up the vehicle, check engine‑light functionality, attach an OBD‑II scan tool, and download emission system data. The technician prints your inspection report. Common failure reasons include a lit check‑engine light, incomplete readiness monitors, or no module communication. If the vehicle fails, you receive a list of repair facilities, complete repairs, then return for retest. Costs vary by station, and successful test results are needed to complete registration renewal.