SAE J 1979-2-2026

E/E Diagnostic Test Modes: OBDonUDS

SAE J1979-2 describes the communication between the vehicle’s OBD systems and test equipment required by OBD regulations. OBD regulations require passenger cars and light-, medium-, and heavy-duty trucks to support a minimum set of diagnostic information to external (off-board) “generic” test equipment.   To achieve this, SAE J1979-2 is based on the Open Systems Interconnection (OSI) Basic Reference Model in accordance with ISO/IEC 7498-1 and ISO/IEC 10731, which structures communication systems into seven layers. When mapped on this model, the services specified are broken into:       Diagnostic services (layer 7), specified in:      ISO 14229-1     SAE J1979-2 OBDonUDS     Presentation layer (layer 6), specified in:      SAE J1930, SAE J1930DA     SAE J1979DA     SAE J2012, SAE J2012DA     SAE J1939DA, SAE J1939-73     Session layer services (layer 5), specified in:      ISO 14229-2     Transport layer services (layer 4), specified in:      DoCAN: ISO 15765-2 Transport protocol and network layer services     ISO 15765-4 Requirements for emissions related systems     DoIP: ISO 13400-2 Road vehicles - Diagnostic communication over Internet Protocol (DoIP) - Part 2: Transport protocol and network layer services     Network layer services (layer 3), specified in:      DoCAN: ISO 15765-2 Transport protocol and network layer services     ISO 15765-4 Requirements for emissions related systems     DoIP: ISO 13400-2 Road vehicles - Diagnostic communication over Internet Protocol (DoIP) - Part 2: Transport protocol and network layer services     Data link layer (layer 2), specified in:      DoCAN: ISO 15765-4, ISO 11898-1, ISO 11898-2     DoIP: ISO 13400-3 Road vehicles - Diagnostic communication over Internet Protocol (DoIP) - Part 3: Wired vehicle interface based on IEEE 802.3     Physical layer (layer 1), specified in:      DoCAN: ISO 15765-4, ISO 11898-1, ISO 11898-2, in accordance with  Table 1     DoIP: ISO 13400-3 Road vehicles - Diagnostic communication over Internet Protocol (DoIP) - Part 3: Wired vehicle interface based on IEEE 802.3          NOTE:   SAE J1979-2 provides a STANDARD to satisfy known country-specific OBD regulations. SAE J1979-2 is not considered a final authority for interpretation of the OBD regulations, so users of this document should determine the applicability of capabilities defined in this document for their specific OBD regulatory requirements.