The SAE J1939
An overview of the J1939 family of standards and how they are used
Since its publication more than a decade ago, SAE J1939 has become widely accepted as the Controller Area
Network (CAN) for on-highway trucks, off-highway equipment, agricultural equipment, construction equipment,
and other vehicles.
What is J1939?
From the Foreword to J1939 (Serial Control and Communications Heavy Duty Vehicle Network)...
“The SAE J1939 communications network is a high speed ISO 11898-1 CAN-based communications
network that supports real-time closed loop control functions, simple information exchanges, and diagnostic
data exchanges between Electronic Control Units (ECUs), physically distributed throughout the vehicle.
The SAE J1939 common communication architecture strives to offer an open interconnect system that
allows ECUs associated with different component manufacturers to communicate with each other.”
J1939 covers the design and use of devices that transmit electronic signals and control information among
vehicle components. Used as an application layer, J1939 provides communication between the engine control,
transmission control, vehicle body control, and other applicable sub-control systems.
J1939 also deﬁnes message timeouts, how large messages are fragmented and reassembled, the network
speed, the physical layer, and how applications acquire network addresses.
The J1939 communications network is deﬁned using a collection of individual SAE J1939 documents based
upon the layers of the Open System Interconnect (OSI) model for computer communications architecture.
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