SAE J1978-2_202412

SAE J1978-2 specifies a complementary set of functions to be provided by an OBD-II scan tool. These functions provide complete, efficient access to all regulated OBD services on any vehicle that is compliant with SAE J1979-2 and SAE J1979-3 The content of this document is intended to satisfy the requirements of an OBD-II scan tool as required by current U.S. OBD regulations. This document specifies: A means of establishing communications between an OBD-equipped vehicle and an OBD-II scan tool. A set of diagnostic services to be provided by an OBD-II scan tool in order to exercise the services defined in SAE J1979-2. The presentation of the SAE J1978 document family, where SAE J1978-2 covers second generation protocol functionality defined in SAE J1979-2, and SAE J1978-1 covers first generation protocol functionality defined in SAE J1979 and protocol determination for both SAE J1979 and SAE J1979-2. The SAE J1978 document family does not preclude the inclusion of additional capabilities or functions in an OBD-II scan tool. However, it is the responsibility of the OBD-II scan tool designer to ensure that no such capability or function can adversely affect either an OBD-equipped vehicle, which may be connected to the OBD-II scan tool, or an OBD-II scan tool itself. Differences in the SAE J1978-2 requirements are highlighted by bold italic text in the technical requirements sections of this document. This SAE Recommended Practice is the second recommended practice in the SAE J1978 family of documents. This document, SAE J1978-2, reflects a task force decision to embark on a family of documents approach for SAE J1978 OBD-II scan tool. SAE J1978-2 content has been generated with content from SAE J1978, technical reference to SAE J1979-2, and regulation requirements. The evolution of the SAE J1978 family of documents is illustrated in Figure 1. Changes that have been made to related SAE documents (e.g., SAE J1979) will also affect the content of this document, requiring changes herein. For reference, the evolution of the SAE J1979 family of documents is illustrated in Figure 2.