SAE - J1939-03
On-Board Diagnostics Implementation Guide
|Publication Date:||1 May 2021|
SAE J1939-03 provides requirements and guidelines for the implementation of on-board diagnostics (OBD) on heavy-duty vehicles (HDV) using the SAE J1939 family of standards. The guidelines identify where the necessary information to meet OBD regulations may be found among the SAE J1939 document set. Key requirements are identified here to ensure the interoperability of OBD scan tools across individual OBD-compliant vehicles.
Market-defined regulations permit the use of SAE J1939 to meet OBD requirements. Implementers are cautioned to obtain and review the specific regulations for the markets where their products are sold. This document is focused on guidelines and requirements to satisfy the State of California Air Resources Board (CARB), the authors of 13 CCR 1971.1, United States Environmental Protection Agency, Euro IV and V requirements from European Commission directives, and UN/ECE WP 29 GRPE WWH OBD Global Technical Regulation (GTR).
Identification of HDV Diagnostic Methods
There are three approaches for providing OBD services. SAE J1939 provides OBD services that are integrated with known powertrain control messages and methods for HDV. This document focuses on the use of SAE J1939 to satisfy OBD requirements.
ISO 15765-4 and ISO 27145 are identified as comparative references. These standards define methods for on-board diagnostics communications that are independent of vehicle's powertrain control and information methods. The three approaches are identified below.
SAE J1939 Approach for HD OBD, OBD II, and WWH OBD
SAE J1939 provides an open systems approach for the integration of HDV components. Within this approach, diagnostic methods and messages are provided to achieve HD OBD, OBD II, and WWH OBD requirements. This specification provides guidelines and requirements for the implementation of HD OBD, OBD II and WWH OBD requirements using SAE J1939 constructs.
The SAE J1939 series of standards does not define scan tool standards in a document structure that is equivalent to SAE J1978 (ISO 15031-4) or ISO 27145. In SAE J1939, standardized scan tools are applications of the requirements given in SAE J1939, SAE J1939DA, SAE J1939-01, SAE J1939-21, SAE J1939-31, SAE J1939-71, SAE J1939-73, SAE J1939-81, and SAE J1939-84. Section 4 discusses the SAE J1939 document structure and its application to scan tools. Subsequent sections discuss topics of particular interest in the development of standardized scan tool for SAE J1939.
ISO 15765 Approach for HD OBD and OBD II
ISO 15765-4 may be used as described therein to satisfy HD OBD and OBD II requirements for heavy-duty vehicles. ISO 15765-4 outlines the individual parts that comprise the diagnostic requirements for OBD. If ISO 15765 is selected, the implementer shall follow the directives given in ISO 15765-4. Under ISO 15765-4, ISO 15031 describes OBD service tool requirements and the OBD message interface in ISO-15031-4 and ISO 15031-5. SAE J1978 is equivalent to ISO 15031-4, and SAE J1979 is equivalent to ISO 15031-5.
ISO 27145 Approach for WWH OBD
ISO 27145 defines data and messaging to satisfy WWH OBD requirements. Implementers may choose to fulfill ISO 27145 when required to meet WWH OBD requirements in local regulations. ISO 27145 defines a VOBD concept for providing a logical function for vehicle-level on-board diagnostics using wireline ethernet and wireline CAN. The logical function may be implemented as a gateway or virtually within one or more compliant modules. This document discusses the process required when implementing the VOBD function for WWH OBD using messages defined in SAE J1939-73. Presently, GTR 5 is best represented in Annex 9b of UN ECE R49.
Verification of OBD Requirements
CARB and U.S. EPA regulations require verification of OBD requirements to assure standardized scan tool interoperation. Compliance to standardized communication requirements for scan tools is determined by SAE J1939-84 and SAE J1699-3.
SAE J1939-84 provides methods to verify interaction between the service tool and vehicle for the SAE J1939 approach. SAE J1939-84 standardizes the qualification of vehicles for use with HD OBD and OBD II scan tools that support SAE J1939. SAE J1939-84 adapts the concepts of SAE J1699 as enabled by SAE J1979DA, SAE J1939-73, SAE J1939-71, and SAE J1939-21.
SAE J1699-3 describes the qualification of vehicles for use with scan tools for the ISO 15765-4/ISO 15031-4 approach. SAE J1699-3 does not apply to vehicles using SAE J1939 diagnostics.
The WWH OBD GTR recognizes SAE J1939-73 as a means to support WWH OBD. This document supports the definitions in SAE J1939-73 with specific requirements and process guidelines to eliminate misinterpretation of the messages defined in SAE J1939-73. Specific requirements for formal evaluation of engines or vehicles are not defined within the GTR.