New York State Banner
D E C banner
D E C banner

Onboard Diagnostics

A vehicle's Onboard Diagnostic (OBD) system is computer software that is installed into a vehicle's onboard computer. The engine and emission controls are monitored and controlled by the OBD system. The OBD system helps to ensure that the emission controls operate properly throughout a vehicle's lifetime. If the OBD system finds a problem that could cause emissions to go over federal standards, it alerts a driver to the problem by lighting up the "Check Engine" light. OBD also helps repair technicians find and repair problems by storing a "trouble code" for each malfunction.

The first OBD systems were introduced in the early 1980s as electronic systems replaced mechanical systems in automobiles. The 1990 Clean Air Act Amendments required manufacturers to put a new generation of OBD (OBD II) on all 1994 and newer cars and light-duty trucks. OBD II systems have increased and more sophisticated detection and monitoring capabilities than the original OBD I systems.

Important OBD Facts

  • If your car or truck was manufactured in 1996 or later, it has a built-in OBD II computer system that monitors the engine and emissions control system.
  • The onboard computer turns on the "Check Engine" light if it finds a problem with your vehicle's operation.
  • If your "Check Engine" light comes on, you should have your car serviced by a professional technician as soon as possible.
  • New York State is moving to incorporate OBD II testing for model year 1996 and newer vehicles into its emissions testing program in the future.
  • The new technology and testing procedures may help you prevent costly repairs by flagging small problems before they become larger ones. Responding to the "Check Engine" light in a timely fashion can improve driving ability and fuel efficiency, enhance your vehicle's performance, and protect the environment by reducing vehicle emissions.
  • OBD II aids automotive technicians in finding and repairing emission related problems.