ISO 27145-4:2012 defines the requirements to successfully establish, maintain and terminate communication with a vehicle that implements the requirements of the World-Wide Harmonized On-Board Diagnostic Global Technical Regulations (Global technical regulation No. 5). This requires plug and play communication capabilities for the vehicle as well as for any test equipment that intends to establish communication with a vehicle. ISO 27145-4:2012 details all the OSI layer requirements to achieve this goal.

ISO 27145-4:2012 is intended to become the single communication standard for access to information relating to vehicle on-board diagnostics (VOBD). To allow for a smooth migration from the existing communication standards to this future world-wide standardized communication standard, the communication concept as specified in ISO 27145-4:2012 is based on two different data links:

• Diagnostic communication over Controller Area Network (DoCAN), ISO 15765-4;
• Diagnostic communication over Internet Protocol (DoIP), ISO 13400 (all parts).

Use cases deriving from country-specific implementation of Global Technical Regulation No. 5 into local legislation are not included in ISO 27145-4:2012.