SAE J 1979-2:2026-04-21

E/E Diagnostic Test Modes: OBDonUDS

Preview

Description

Features

Life cycle

Historical

Collections

Summary

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.