The J1939 protocol was initially designed as a dedicated communication and diagnostics protocol for the complex networks of huge vehicles. It is commonly used in heavy-duty vehicles such as
Trucks, Tractors, Trailers, Agriculture vehicles, Material handling machines, Marine propulsion Aid and Rescue, and many other off-road vehicles.
 
Today, it is widely recognized by diesel engine manufacturers across the world.
 
J1939 provides diagnostic data such as:
- Vehicle engine speed
- temperature
- oil temperature
- exhaust emissions
- and other customizable options
 
It also:
              • Specifies how to handle multi-packet messages.
              • Enable communication across large complex networks.
              • Specifies how to convert data into human-readable information.
              • Defines diagnostics interface of its own.