This document defines the requirements for the external test equipment as:

—？a means of establishing communications between a WWH-OBD-equipped vehicle and external test equipment;

—？a set of diagnostic services, including addressing methods, to be provided by the external test equipment in order to exercise the services defined in ISO？27145？3.

This document describes the minimum capabilities or functions in the external test equipment. Additional functionalities, for example, non WWH-OBD protocols or retrieval of repair and maintenance information, can be integrated into the external test equipment according to the test equipment manufacturer needs. The external test equipment designer ensures that no such capability or function can adversely affect either a WWH-OBD-equipped vehicle connected to the equipment, or the equipment itself.

When the external test equipment implements functionality, which is not covered by ISO？27145？3, this functionality is not linked to the timing requirements defined in this document.