Editing On-board diagnostics (section)

{{Short description|Automotive engineering terminology}}
{{Use mdy dates|date=March 2020}}
{{Use British English|date=June 2024}}
[[File:MaxScan OE509 collage.jpg|thumb|right|Various views of a "MaxScan OE509" – a fairly typical onboard diagnostics (OBD) scanner, 2015.]]

'''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 [[United States vehicle emission standards|federal emissions standards]] to detect failures that may increase the vehicle tailpipe [[Air pollution|emissions]] to more than 150% of the standard to which it was originally certified.<ref>{{Cite web |last=CarTechBooks |title=OBD-I & OBD-II: A Complete Guide to Diagnosis, Repair & Emissions Compliance |url=https://www.cartechbooks.com/products/obd-i-amp-obd-ii-a-complete-guide-to-diagnosis-repair-amp-emissions-compliance |access-date=2023-09-15 |website=CarTechBooks}}</ref><ref>{{cite web |url=https://www.epa.gov/regulations-emissions-vehicles-and-engines |title=Regulations for Emissions from Vehicles and Engines |date=April 15, 2016 |publisher=[[US Environmental Protection Agency]] |access-date=2024-06-02}}</ref>

OBD systems give the vehicle owner or repair technician access to the status of the various vehicle sub-systems. The amount of diagnostic information available via OBD has varied widely since its introduction in the early 1980s versions of onboard vehicle computers. Early versions of OBD would simply illuminate a [[Tell-tale (automotive)|tell-tale]] light if a problem was detected, but would not provide any information as to the nature of the problem. Modern OBD implementations use a standardized digital communications port to provide [[real-time data]] and [[Table of OBD-II Codes|diagnostic trouble codes]] which allow malfunctions within the vehicle to be rapidly identified.