What is CAN

Since the first car was built by Daimler Benz, cars have only ever gotten more complicated. In modern cars a vast array of modules, sensors, and motors provide many of the creature comforts, smooth operation of the cars systems, and a margin of safety. But as these systems expanded with new technologies a few problems arose. The number of sensors (oftentimes redundant), signal integrity, and the sheer complication of the network of connections and wiring needed to run everything properly.

But What is CAN?

CAN bus was a communication protocol introduced by Robert Bosch GmbH in the 1980’s, but it wasn’t really adopted heavily in automotive use until the late 90’s. By 2006 70% of cars utilized CAN communication, and all vehicles sold in the United States after 2008 were required to follow the CAN BUS Protocol. This method of building an automotive network works well for a few reasons. CAN Bus offers a secure method of transmitting the information with very minimal signal interference from things like electro-magnetic waves. It also enables multiple modules to use the same sensors and information allowed to all of the other modules reducing redundancy. Lastly it simplifies the wiring, only two wires need to be run to the module or system in question rather than individually wiring each sensor to each module.

Traditional Automotive Communication Network

There are a huge number of sensors on modern cars. In addition to all the sensors involved in engine control, you run into sensors for things like climate control, ABS, airbags, security, Lane Change Assist, self-parking, trunk position and pretty much every other feature on your car. Previously things like ABS and vehicle speed would have required different sensors, but now one module is able to take the signal from the wheel speed sensors and supply them to any other module that asks for that information.

In a traditional automotive network there were all sorts of additional wires required, to properly run signal to each of the sections. This became quite complicated very quickly.

CAN Network

In a CAN network only two wires are needed to connect to each of the sensors and modules. These are called CAN High and CAN Low. This simplicity allows for a significantly easier network for communication.

An example of the CAN network practice is the typical Auto start/stop system. At any given moment the ECU will talk to the ABS system in order to figure out how fast the car is moving from the wheel speed sensors. It will talk to the climate control system to find out if the air conditioning is on, the charging system to make sure the car has adequate power, and then it will talk to the engine to see if the conditions are safe to turn off the car.