SAE J1939

SAE J1939, a set of standards defined by the Society of Automotive Engineers (SAE), is primarily used for communication and diagnostics in heavy-duty vehicles like trucks, buses, and construction equipment, as well as other commercial vehicles.

J1939 defines how Electronic Control Units (ECUs) transmit data over the Controller Area Network (CAN) bus protocol, enabling communication and diagnostics between vehicle components. 

It creates a universal shared "language" for devices to interact, allowing heavy-duty vehicles to be fitted with devices from different manufacturers without worrying about incompatibility.