The On-Board Diagnostics II (OBD-II) port is used to access the vehicle's computer for various tasks, such as emissions tests and diagnostics. The OBD port is where the Hum System is installed so that the network can communicate with the vehicle directly. the OBD port's power pin (battery positive 16): MUST be Unswitched (always connected to battery power) Get Best Quality OBD Port for your vehicle at mapout24.com