m a x A I 4 3 0 & m a x A I 4 3 0 v T E C H N I C A L M A N U A L
48
Rev A 8/24/2020
4. Understanding Data-Bus Operation
… data-bus is like an information super-highway in the vehicle…
4.1 Data-Bus Basics
While this information applies to many types of data-busses, the maxAI 430i operates exclusively over the
SAE J1939 data-bus.
The data-bus is like an information super-highway in the vehicle. A data-bus allows various controllers,
such as the engine controller, transmission controller, chassis controller, etc. to communicate with each
other and any other components connected to the data-bus.
Most new diesel engines are controlled by an Engine Control Module (ECM) that uses information from
various sensors to adjust operating parameters, such as fuel injection, to optimize power, increase fuel
economy, and lower emissions. The data-bus enables the ECM to send/receive vast amounts of
information to/from the transmission computer or any other computer connected to the data-bus, greatly
simplifying the vehicle’s electrical system.
The data-bus contains most operating information about the vehicle, such as engine and vehicle speed,
coolant and oil temperatures, oil and fuel pressures, as well as error codes from the various controllers.
4.2 Data-Bus Hardware
The physical aspects of the data-bus are quite simple. It’s
nothing more than a pair of wires twisted together,
commonly referred to as a twisted pair, running from one
controller to another.