Description:
Multiplexing technology involves
the use of multiple onboard computers, all linked
together in the same circuit (called
a bus). Each computer
in the link is
capable of "talking" with
the other computers, using a specific language known
as a protocol.
Purpose: Historically, carmakers added
more wire to a car's harness each time an electrical accessory was
added. As creature comforts grew in popularity during the '70s, it
was easy to see that a car laden with electrical add-ons would
require many more runs of copper wire to carry the necessary power,
ground and signal circuits required to operate all of the equipment.
This problem grew exponentially in the early '80s when onboard
computers began to proliferate. A network
of sensors and actuators compounded wiring requirements significantly and the
use of multiple onboard computers soon became
attractive. Given all this complexity, multiplexing technology actually allows simplification
of circuits, Rather than using a dedicated circuit for
each computer, multiplexing uses
a common circuit
and a dedicated
message for each computer in the multiplexed network.
Maintenance Tips/Suggestions: The benefits of multiplexing also spill
over into the diagnostics arena. Since the onboard computers are
able to “talk” to one another, they’re able to share information
about system problems as well. Using the appropriate diagnostic
tool, a trained service
technician can tap into the
system to extract operating information and diagnostic trouble
codes if a system fault
occurs.
