Even the most basic vehicles include many electronically controlled systems. If each electronic system had its own ECU, harness and sensors, the weight of the added components would negate any efficiency it provided. A vehicles' multiple electronic systems could require over 1 mile or 1.6 Kilometers of insulated wiring, consisting of around 1000 individual wires and many terminals.
One solution to the problem is the use of a system that integrates sensors into a common wiring harness by combining all the individual systems, where possible, into a multiplexed serial communications network, so they can share the information.
An added advantage of such a system is that if there is less wire and fewer connections there is less chance of dirty connections causing faults.
This system is referred to as a Controlled Area Network BUS or CAN BUS and it uses two thin wires to connect, or multiplex, all the control units and their sensors to each other. The output devices are referred to as Nodes.
The advantage of a multiplex network is that it enables a decreased number of dedicated wires for each function, and therefore a reduction in the number of wires in the wiring harness, reduced system cost and weight, improved reliability, serviceability, and installation.
In addition, common sensor data, such as vehicle speed, engine temperature, etc. are available on the network, so data can be shared, thus reducing the number of sensors.
Also, networking allows greater vehicle content flexibility because functions can be added or modified through software changes.
Other control units can be added to the system by simply connecting them to the network.
A diagnostic tool can be connected to the CANBUS to extract operational information to assist in diagnosis and fault finding.