what is 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 a different physical layer, it is used between the tractor and trailer.This is specified in ISO 11992.ll J1939 packets, except for the request packet, contain eight bytes of data and a standard header which contains an index called Parameter Group Number (PGN), which is embedded in the message's 29-bit identifier.