The 1990 Federal Clean Air Act requires New York State to conduct an inspection program to help reduce harmful emissions from most passenger cars and light-duty trucks. The emissions inspection is done at the same time as the annual safety inspection. Vehicles that fail the emissions inspection may not be able to become registered or, if already registered, the registration may not be renewed.

On-Board Diagnostics Generation II (OBDII) Inspection
Most 1996 or newer gasoline-powered vehicles and most 1997 or newer diesel-powered vehicles that have a gross vehicle weight rating (GVWR) less than 8,501 pounds are subject to the OBDII emissions inspection. This test examines the Malfunction Indicator Lamp (MIL), also known as the "check engine" light, for operation/illumination, and verifies the test results of the vehicle's "on-board emissions diagnostic" system.

Low Enhanced Inspection.
A "Low Enhanced" emissions inspection is required for most other vehicles, unless they are subject to the OBDII test or are exempt from all emissions inspections. This inspection is required for all vehicles from and including model year 1995 and older, through and including vehicles that are up to 25 model years old, and that weigh 18,000 lbs. or less.

Each emissions inspection for gasoline-powered vehicles confirms the presence and connection of the vehicle's required emissions control devices. This includes making sure that the vehicle's gas cap is present, is in good condition, and fits properly.