On-board diagnostics (OBD) is a term referring to a vehicle's self-diagnostic and reporting capability. In the United States, this capability is a requirement to comply with federal emissions standards to detect failures that may increase the vehicle tailpipe emissions to more than 150% of the standard to which it was originally certified. [1][2]
The OBD port is an electrical plug that OBD-II scanners, code readers, and other devices can be plugged into to access the OBD-II system. It is also the port that is typically used for state vehicle inspections.
OBD systems monitor emissions to ensure that vehicles meet minimum requirements at all times. They also alert users when emissions exceed acceptable limits so that the issue can be addressed and fixed before an inspection.
OBD stands for “ O n- B oard D iagnostics.” It is a computer-based system originally designed to reduce emissions by monitoring the performance of major engine components.