# OBD-II **slug:** `obd-ii` · **URL:** `/knowledge/glossary/obd-ii/` · **category:** Automotive · **reviewer:** Tatiana ### Definition OBD-II (On-Board Diagnostics II) is the standardized diagnostic interface required on light-duty vehicles sold in most international markets. It exposes the vehicle's diagnostic protocol — typically over a CAN bus — through a physical 16-pin connector accessible from the driver's footwell. ### What it means Mandated in the United States from model year 1996 and adopted internationally with regional variants (EOBD in the European Union, JOBD in Japan, CN-OBD in China), the OBD-II interface was designed for emissions and diagnostic purposes. It exposes parameter IDs (PIDs) for engine, transmission, and emissions data, plus the ability to clear diagnostic trouble codes (DTCs). From a security perspective, OBD-II is the most common entry point for in-vehicle network attacks. The connector exposes raw CAN bus access without authentication. A connected OBD-II dongle (commercial telematics device, insurance monitoring, fleet management) extends this exposure to the cellular or Bluetooth network the dongle uses. For Melina engagements, OBD-II testing covers: dongle firmware and cellular path security, CAN gateway behavior when OBD-II traffic appears, and the manufacturer's authentication strategy on diagnostic services (UDS — Unified Diagnostic Services per ISO 14229). ### Related terms - [CAN bus](/knowledge/glossary/can-bus/) - [ECU](/knowledge/glossary/ecu/) - [DoIP](/knowledge/glossary/doip/) (P1.5) ### Authoritative sources - [ISO 15031 (vehicle communication for off-board OBD)](https://www.iso.org/standard/66368.html) - [SAE J1979-DA (E/E diagnostic test modes)](https://www.sae.org/standards/content/j1979-da_202304/) ---