SAE J1939 Standard


SAE J1939 is a standard communication protocol for trucks and busses implemented over a CAN bus. Common on electronically-controlled diesel engines and transmissions, J1939 brings advanced capabilities to any mobile machine.

STW has developed a software suite to send and receive data in SAE J1939 format, easing implementation of applications such as engine load control, drive-by-wire, and intelligent transmission control.

SAE J1939 makes use of the 29-bit extended identifiers available in CAN 2.0B, as opposed to the 11-bit identifiers used in other protocols. SAE J1939 defines an index called the Parameter Group Number or PGN, which is embedded in the message’s 29-bit identifier. A PGN identifies a message’s function and associated data into a wide range of predefined parameters known as SPNs. Parameters such as engine RPM or oil temperature can be accessed by capturing messages with the associated PGN. A range of PGNs is also reserved for proprietary use, allowing users to add custom messages without interfering with the standard messages.