Editing CAN bus (section)

=== Automotive ===
The modern automobile may have as many as 70 [[electronic control unit]]s (ECUs) for various subsystems.<ref>Comparison of Event-Triggered and Time-Triggered Concepts with Regard to Distributed Control Systems A. Albert, Robert Bosch GmbH Embedded World, 2004, Nürnberg</ref> Usually the biggest processor is the [[engine control unit]]. Others are used for autonomous driving, advanced driver assistance system (ADAS), [[Transmission (mechanics)|transmission]], [[airbag]]s, [[Anti-lock braking system|antilock braking/ABS]], [[cruise control]], electric [[power steering]], audio systems, [[power window]]s, doors, mirror adjustment, battery and recharging systems for hybrid/electric cars, etc. Some of these form independent subsystems, but communication among others is essential. A subsystem may need to control actuators or receive feedback from sensors. The CAN standard was devised to fill this need. One key advantage is that interconnection between different vehicle systems can allow a wide range of safety, economy and convenience features to be implemented using software alone - functionality which would add cost and complexity if such features were ''hard wired'' using traditional automotive electrics. Examples include:

* [[Start-stop system|Auto start/stop]]: Various sensor inputs from around the vehicle (speed sensors, steering angle, air conditioning on/off, engine temperature) are collated via the CAN bus to determine whether the engine can be shut down when stationary for improved fuel economy and emissions.
* [[Electric park brake]]s: The ''[[Hill-holder|hill hold]]'' functionality takes input from the vehicle's tilt sensor (also used by the burglar alarm) and the road speed sensors (also used by the ABS, engine control and traction control) via the CAN bus to determine if the vehicle is stopped on an incline. Similarly, inputs from seat belt sensors (part of the airbag controls) are fed from the CAN bus to determine if the seat belts are fastened, so that the parking brake will automatically release upon moving off.
* [[Automatic parking|Parking assist]] systems: when the driver engages reverse gear, the transmission control unit can send a signal via the CAN bus to activate both the parking sensor system and the door control module for the passenger side door mirror to tilt downward to show the position of the curb. The CAN bus also takes inputs from the rain sensor to trigger the rear windscreen wiper when reversing.
* Auto [[lane assist]]/[[collision avoidance]] systems: The inputs from the parking sensors are also used by the CAN bus to feed outside proximity data to driver assist systems such as Lane Departure warning, and more recently, these signals travel through the CAN bus to actuate [[brake by wire]] in active collision avoidance systems.
* Auto brake wiping: Input is taken from the rain sensor (used primarily for the automatic [[windscreen wiper]]s) via the CAN bus to the ABS module to initiate an imperceptible application of the brakes while driving to clear moisture from the brake rotors. Some high-performance [[Audi]] and [[BMW]] models incorporate this feature.
* Sensors can be placed at the most suitable place, and their data used by several ECUs. For example, outdoor temperature sensors (conventionally placed in the front) can be placed in the outside mirrors, avoiding heating by the engine, and data used by the engine, the climate control, and the driver display.

In recent years, the [[Local Interconnect Network|LIN bus]] (Local Interconnect Network) standard has been introduced to complement CAN for non-critical subsystems such as air-conditioning and infotainment, where data transmission speed and reliability are less critical.