Sae J1979 Standard Download Pdf
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SAE J1979 Standard: An Overview
SAE J1979 is a standard that defines the communication between the vehicle's on-board diagnostic (OBD) systems and external test equipment. It is based on the Open Systems Interconnection (OSI) model, which structures communication systems into seven layers. SAE J1979 covers the diagnostic services (layer 7), the presentation layer (layer 6), and the data link layer (layer 2) of the OSI model. It also references other standards that specify the session layer (layer 5), the transport layer (layer 4), the network layer (layer 3), and the physical layer (layer 1) of the OSI model.
SAE J1979 is aligned with ISO 15031-5, which is the international equivalent of SAE J1979. Both standards are intended to support the legislated emissions-related OBD requirements across different regions and vehicles. SAE J1979 also references several SAE documents that contain all terms, data and diagnostic trouble code (DTC) definitions, such as SAE J1930, SAE J1979-DA, and SAE J2012-DA.
SAE J1979 supports different protocols for data transmission, such as CAN (ISO 15765-4), SAE J1850, ISO 9141-2, and K-Line (ISO 14230-4). Depending on the protocol used, different diagnostic services are available. For example, ISO 14229-2 supports session layer services for CAN and K-Line protocols, but not for SAE J1850 and ISO 9141-2 protocols.
SAE J1979 defines various diagnostic test modes that allow external test equipment to request information from the vehicle's OBD systems. These test modes include:
Mode $01: Request current powertrain diagnostic data
Mode $02: Request freeze frame data
Mode $03: Request emission-related DTCs
Mode $04: Clear/reset emission-related diagnostic information
Mode $05: Request oxygen sensor monitoring test results
Mode $06: Request on-board monitoring test results for specific monitored systems
Mode $07: Request emission-related DTCs detected during current or last completed driving cycle
Mode $08: Request control of on-board system, test or component
Mode $09: Request vehicle information
Mode $0A: Request emission-related DTCs with permanent status
To request or display data using these test modes, standardized data items are used, such as parameter IDs (PIDs), test IDs (TIDs), monitor IDs (MIDs), and information type IDs (InfoType IDs). These data items are defined in SAE J1979-DA.
To download a PDF version of SAE J1979 standard, you can visit SAE International website[^1^] or SAE International website[^2^], depending on the revision you need. You may need to purchase the standard or have a subscription to access it.SAE J1979 standard is an important document for vehicle manufacturers, test equipment manufacturers, regulators, and service technicians who need to communicate with the vehicle's OBD systems. It ensures a common and consistent way of accessing and displaying diagnostic information across different vehicles and regions. It also helps to monitor and reduce the emissions from vehicles and improve their performance and reliability.
SAE J1979 standard is updated periodically to reflect the changes in technology and regulations. The latest revision of SAE J1979 was published in February 2017, which incorporated the changes from ISO 15031-5:2015. Some of the changes include:
Adding new PIDs for hybrid/electric vehicles, diesel vehicles, and alternative fuels
Adding new InfoType IDs for vehicle identification number (VIN), calibration identification (CALID), calibration verification number (CVN), and exhaust gas sensor properties
Adding new DTCs for hybrid/electric vehicles, diesel vehicles, and alternative fuels
Adding new test modes for WWH-OBD (Worldwide harmonized OBD)
Clarifying the use of negative response codes (NRCs) and functional addressing
Aligning the terminology and definitions with other standards
SAE J1979 standard is a valuable resource for anyone who is interested in or involved in vehicle diagnostics. It provides a comprehensive and detailed description of the diagnostic services, data items, DTCs, and protocols that are used for OBD communication. It also provides examples and annexes that illustrate the use of SAE J1979 in different scenarios. 061ffe29dd