Welcome to the Connecticut Emissions Program

Emissions testing using the On-Board Diagnostic system or OBD testing is the quickest and most efficient of all emissions tests. The vehicle’s internal computer, which continuously monitors the engine, transmission and emissions control systems are tested. The OBD test is, in effect, an “early warning system” that alerts you to the need for repairs that can reduce air pollution and ensure that your vehicle keeps running as cleanly as it was designed to run.

The inspector will connect a communication cable from the emissions testing equipment to your vehicle’s Diagnostic Link Connector or DLC. Through the cable, the emissions testing equipment will request specific communication protocols from your vehicle, allowing the testing equipment to verify whether or not your vehicle emissions control system is in compliance. Information is retrieved from your vehicle; nothing is uploaded or installed on your vehicle.

Vehicles subject to OBD testing include 1996 and newer gasoline-powered and 1997 and newer diesel-powered vehicles with the Gross Vehicle Weight Rating (GVWR) less than 8,501 LBS.

In addition, the following medium-duty vehicles (trucks, vans, larger SUVs) with the GVWR between 8,501 LBS to 10,000 LBS are also subject to OBD testing:

  • 2007 or newer diesel-powered vehicles
  • 2008 or newer non-diesel vehicles (Gasoline, Compressed Natural Gas (CNG), Liquid Propane Gas (LPG), Ethanol and Methanol)

In addition to this test, all vehicles are subject to the visual verification of the catalytic converter; if one or more catalytic converters are missing from your vehicle, the emissions test will fail.

Please click here for more information on OBD testing.