What Is an Electronic Control Unit?

An electronic control unit (ECU) is a small device in a vehicle’s body that is responsible for controlling a specific function. 

Today’s vehicles may contain 100 ECUs or more, controlling functions that range from the essential (such as engine and power steering control) to comfort (such as power windows, seats and HVAC), to security and access (such as door locks and keyless entry). ECUs also control passive safety features, such as airbags, and even basic active safety features, such as automatic emergency braking.

Each ECU typically contains a dedicated chip that runs its own software or firmware, and requires power and data connections to operate. 

An ECU receives inputs from different parts of the vehicle, depending on its function. For example, a door lock ECU would receive input when a passenger pushes the door lock/unlock button on a car door or on a wireless key fob. An airbag ECU would receive inputs from crash sensors and from sensors that detect when someone is sitting in a particular seat. And an automatic emergency braking ECU would receive inputs from forward-facing radars that detect when the vehicle is approaching an obstacle too quickly.

The ECU would then communicate to actuators to perform an action based on the inputs. In our examples, the door lock ECU would activate an actuator that locks or unlocks the corresponding door. The airbag ECU would choose which airbags to deploy, depending on the location of the passengers, and then direct the actuators to deploy them. And the automatic emergency braking ECU would engage the brakes to prevent a collision.

As vehicle manufacturers continue to add features and functions, space is becoming an issue. That is, each new feature requires a new ECU, and OEMs are running out of places to put them. This incremental approach also becomes inefficient.

The next logical step is consolidation, or up-integration, to reduce complexity and make better use of space. Aptiv’s Smart Vehicle Architecture™ puts control of multiple functions into a domain controller. Safety features, for example, can be consolidated into a controller focused on safety, with features running in parallel software applications on the same hardware. With this approach, the role of dedicated ECUs will diminish as they are up-integrated into domain controllers, and the industry continues to move toward a future of software-defined vehicles.

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