scope:

Introduction

SAE J1979-2 describes the communication between the vehicle's OBD systems and test equipment required by OBD regulations. On-Board Diagnostic (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

○ 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, -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, -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.