Tracked Changes. Road vehicles. Implementation of World-Wide Harmonized On-Board Diagnostics (WWH-OBD) communication requirements. Connection between vehicle and test equipment|Diagnostic programs, Road vehicles, Communication equipment, Session layer (OSI), Electronic equipment and components, Information exchange, Data link layer (OSI), Physical layer (OSI), Diagnostic testing, Vehicle components, Road vehicle components, Road vehicle engineering, Open systems interconnection, Network layer (OSI), Data transmission, Transport layer (OSI), Data transfer