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On-Board Diagnostics (OBD)

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Repair Technicians State Agencies Vehicle Owners Vehicle & Engine Manufacturers

On-Board Diagnostics, or "OBD," is a computer-based system built into all 1996 and later light-duty vehicles and trucks, as required by the Clean Air Act Amendments of 1990. OBD systems are designed to monitor the performance of some of an engine's major components including those responsible for controlling emissions.

OBD impacts many audiences for different reasons.

  • For Repair Technicians:
    • OBD is a valuable tool that assists in the service and repair of vehicles by providing a simple, quick, and effective way to pinpoint problems by retrieving vital automobile diagnostics from the OBD systems.
    • This site will help you find information about OBD regulatory and technical issues and the availability of service information needed to diagnose and repair OBD problems.
  • For State Agencies:
    • OBD plays an important role where vehicle inspection and maintenance programs are required.
    • This site will help you find information on program implementation guidance and outreach materials to help raise awareness about OBD in your state or locality.
  • For Vehicle Owners:
    • OBD serves as an early warning system that alerts you to the potential need for vehicle repair through the "Check Engine" light on the dashboard of your vehicle.
    • This site will help you find information on the benefits of OBD and the important role OBD plays in responsible car care and learn other ways you can maintain your vehicle and reduce its emissions.
  • For Vehicle and Engine Manufacturers:
    • OBD systems are required by EPA to be installed on light-duty vehicles and trucks, as well as heavy-duty engines.
    • This site will help keep you informed of EPA's regulatory efforts, policies, and guidelines regarding OBD, including any issues that might impact your design and manufacturing process.

This page is maintained by EPA's Office of Transportation and Air Quality (OTAQ).
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