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