This part of ISO 22900 specifies the diagnostic protocol data unit application programming interface (D-PDU API) as a modular vehicle communication interface (MVCI) protocol module software interface and common basis for diagnostic and reprogramming software applications. This part of ISO 22900 covers the descriptions of the application programming interface (API) functions and the abstraction of diagnostic protocols, as well as the handling and description of MVCI protocol module features. Sample MVCI module description files accompany this part of ISO 22900. Migration from and to the existing standards SAE J2534-1 and RP1210a is addressed. This part of ISO 22900 contains a description of how to convert between the APIs. Corresponding wrapper APIs accompany this part of ISO 22900. The purpose of this part of ISO 22900 is to ensure that diagnostic and reprogramming applications from any vehicle or tool manufacturer can operate on a common software interface, and can easily exchange MVCI protocol module implementations.