The following article describes detail information regarding the Multiplex Wiring System applied on automotive industry.
In a multiplex system the control functions will be distributed around the vehicle and complex interconnections between diagnostic terminals, sensors, instruments and switches will not add to the harness complexity. Multiplex wiring system potentially seems to be a good replacement for conventional wiring system. Reduced complexity, increased flexibility and diagnostic capability could be achieved by incorporating microcontroller devices at nodes within the wiring system.
Get more information about the Car Multiplex Wiring System here (source: national.com)