ISO 13400-3:2016 specifies the vehicle communication interface and test equipment requirements for a physical and data link layer based on IEEE 802.3 100BASE-TX. This interface serves as the physical basis for IP-based communication between the vehicle and test equipment. This document specifies the following aspects: - requirements for signal and wiring schematics in order to ensure physical layer compatibility of the vehicle interface and Ethernet networks and test equipment communication interfaces; - discovery/identification of the in-vehicle diagnostic Ethernet interface; - activation and deactivation of the in-vehicle diagnostic Ethernet interface; - mechanical and electrical diagnostic connector requirements; - this edition has been modified to include the identification of two Ethernet pin assignments.