In the past, the automotive industry has learned the lesson that competition on the level of bits and bytes, proprietary bus systems, data communication and diagnostic protocols is unrewarding. Too much time and money has been spent on the development of proprietary diagnostic tools. Vehicle manufacturers and suppliers realized that standardization would be the best way to overcome this situation. Furthermore, regulatory requirements in the US and the EU for such standardization have strengthened this lesson.As a result, the automotive industry has standardized the technology for the communication of external test equipment with electronic control units (ECUs) in road vehicles. Standardization serves the price, the quality and the maintainability via scale and training curve effects.This paper contains a technical introduction of internationally standardized diagnostic protocols (UDS on CAN, WWH-OBD, UDSonIP and DoIP), the D-Server (MVCI) with D-Server API and D-PDU API, the diagnostic data format (ODX) and the open test sequence exchange format (OTX). The respective international standards are ISO 14229 (UDS), ISO 27145 (WWH-OBD), ISO 13400 (DoIP), ISO 22900 (MVCI), ISO 22901 (ODX), and ISO 13209 (OTX).