Functions Of Sensors And Actuators

FUNCTIONS OF SENSORS AND ACTUATORS

Name		Function
ABS control module and hydraulic control module (ABSCM & H/U)	ABSCM section	It determines the conditions of the wheels and the vehicle body from the wheel speed data and controls the hydraulic control unit depending on the result. When the ABS is active, the ABSCM provides the automatic transmission control module with control signals which are used by the module for cooperative control of the vehicle with the ABSCM. Whenever the ignition switch is placed at ON, the module performs a self diagnosis sequence. If anything wrong is detected, the module cuts off the system. It communicates with the SUBARU select monitor.
	HU section	When the ABS is active, the H/U changes fluid passages to the wheel cylinders in response to commands from the ABSCM. It constitutes the brake fluid passage from the master cylinder to the wheel cylinders together with the piping.
	Valve relay section	It serves as a power switch for the solenoid valves and motor relay coil. It operates in response to a command from the ABSCM.
	Motor relay section	It serves as a power switch for the pump motor. It operates in response to a command from the ABSCM.
ABS sensor (wheel speed sensor)		They detect the wheel speed in terms of a change in the density of the magnetic flux passing through them and convert it into an electrical signal. The electrical signal is sent to the ABSCM.
Tone wheels		They give a change in the magnetic flux density by the teeth around themselves to let the ABS sensors generate electrical signals.
G sensor		It detects a change in acceleration in the longitudinal direction of the vehicle and outputs it to the ABSCM as a voltage signal.
Stop light switch		It provides information on whether the brake pedal is depressed or not to the ABSCM. The ABSCM uses it to determine ABS operation.
ABS warning light		It alerts the driver to an ABS fault. When the diagnosis connector and diagnosis terminal are connected, the light flashes to indicate a diagnostic trouble code stored in the ABSCM.
Automatic transmission control module		It provides gear controls and changing power transmission to front and rear wheels in response to control signals from the ABSCM.

Fig 1: ABS Circuit Diagram

Courtesy of SUBARU OF AMERICA, INC.