SAE J1939

Society of Automotive Engineers standard SAE J1939 is the vehicle bus recommended practice used for communication and diagnostics among vehicle components. Originating in the car and heavy-duty truck industry in the United States, it is now widely used in other parts of the world.

SAE J1939 is used in the commercial vehicle area for communication throughout the vehicle, with the physical layer defined in ISO 11898. A different physical layer is used between the tractor and trailer, specified in ISO 11992.

History

Originally, CAN was not mentioned in J1939, which covered cars and tractor-trailer rigs, and with some dual and triple use 8-bit addresses assigned by the SAE J1939 board. CAN was not originally free, but its instruction set did fit in the custom instruction format of J1939. This was true as of 2000. Since then, CAN has been included, the chipset for J1939 has been clocked faster, and 16-bit addresses (PGN) have replaced 8-bit addresses.

J1939, ISO 11783 and NMEA 2000 all share the same high level protocol. SAE J1939 can be considered the replacement for the older SAE J1708 and SAE J1587 specifications.