This part of ISO 15031 specifies a minimum set of requirements for a diagnostic connector used in communication between vehicle and external equipment for emissions-related diagnostics. Its aim is to promote the use of a common diagnostic connector throughout the motor vehicle industry. The diagnostic connection consists of two mating connectors, the vehicle connector and the external test equipment connector. Applicable to all types of road vehicles, the connector specified has no positive locking feature and is intended for short-term diagnostic connection only. This part of ISO 15031 specifies functional requirements for a) the vehicle connector, separated into the four principal areas of 1) connector location/access, 2) connector design, 3) connector contact allocation, and 4) electrical requirements for connector and related electrical circuits, and b) the external test equipment connector, separated into the three principal areas of 1) connector design, 2) connector contact allocation, and 3) electrical requirements for connector and related electrical circuits. The dimensional requirements of the vehicle connector are given as a minimum specification, to allow design freedom.