Which component makes physical adjustments in a car's mechanical system?

The component that makes physical adjustments in a car's mechanical system is indeed the actuator. Actuators are responsible for converting electrical signals into mechanical movement. When the vehicle's electronic control unit (ECU), which includes the engine control module (ECM), determines that a change is necessary (such as adjusting the throttle position, moving a valve, or engaging a motor), it sends a signal to the actuator. The actuator then performs the required physical adjustment based on this command.

This function contrasts with other components such as sensors that detect conditions like temperature, pressure, or position and relay that information to the ECU, instead of making adjustments themselves. The computer in this context refers generally to the ECU and is responsible for managing vehicle functions but does not directly make physical adjustments. Therefore, understanding the role of the actuator is crucial, as it is the component that translates electronic signals into physical actions within the car's mechanical system.