BRAKE CONTROL SYSTEM

FUNCTION OF MAIN COMPONENTS

Component		Function
Brake Actuator Assembly		Controls the wheel cylinder pressure of each wheel according to a signal from the skid control ECU assembly.
Brake Master Cylinder Sub-assembly	Master Cylinder	Generates hydraulic pressure in accordance with the brake pedal depression force.
	Brake Stroke Simulator Cylinder Sub-assembly	Provides a pedal stroke during braking in accordance with the driver's pedal effort.
	Brake Master Cylinder Reservoir Assembly	Stores brake fluid for master cylinder control and brake actuator control.
	Brake Fluid Level Warning Switch	Detects a low brake fluid level.
Brake Control Power Supply Assembly		An auxiliary power supply to provide stable electrical power to the brake system. When the voltage of the auxiliary battery is low, the brake control power supply assembly supplements the supply of power to the brake system by providing the electric charge that is stored in the unit.
Combination Meter Assembly	Brake System Warning Light (Red Indicator)	Illuminates to alert the driver that the skid control ECU assembly detects the malfunction in the apportioning of the brake force. Illuminates to inform the driver when the parking brake is on or the brake fluid is low.
	Brake System Warning Light (Yellow Indicator)	Illuminates to alert the driver that a minor malfunction which does not affect the braking force has occurred in the brake system.
	ABS Warning Light	Illuminates to alert the driver when the skid control ECU assembly detects a malfunction in the ABS.
	Slip Indicator Light	Blinks to inform the driver when the TRC, VSC or ABS is operational. Illuminates to alert the driver when the skid control ECU assembly detects a malfunction in the TRC or VSC.
	VSC OFF Indicator Light	Illuminates to inform the driver when VSC OFF mode is selected.
	Master Warning Light	Illuminates when the warning message is displayed in the multi-information display.
	Multi-information Display	Displays the information message when TRC OFF mode is selected. Displays the warning message when the skid control ECU assembly detects a malfunction in the ABS or EBD.
	Multi Buzzer	Sounds to alert the driver when the vehicle is being driven with the parking brake still engaged.
Stop Light Switch Assembly		Detects the brake pedal depressing signal.
Parking Brake Switch Assembly		Detects the parking brake pedal status.
Brake Pedal Stroke Sensor Assembly		Directly detects the extent of the brake pedal stroke operated by the driver.
Combination Switch Assembly	VSC OFF Switch	Enables the driver to select "Normal Mode", "TRC OFF Mode", or "VSC OFF Mode".
Air Conditioning Control Assembly	Hazard Warning Signal Switch	Transmits a hazard warning light on/off request signal to the skid control ECU assembly.
Front Door Courtesy Light Switch Assembly (Driver Side)		Detects whether the driver door is open or closed, sends the information to the skid control ECU assembly and activates the electrically controlled brake system when the door is opened while the power switch is off.
Speed Sensor		Detects the wheel speed of each of the 4 wheels.
Yawrate Sensor		Detects the vehicle's longitudinal and lateral acceleration. Detects the vehicle's yaw rate.
Steering Sensor		Detects the direction and angle of the steering wheel.
Semiconductor PWR Integration ECU	Stop Light Control Relay	Illuminates or flashes the stop lights in accordance with the signals from the stop light switch assembly and skid control ECU assembly.
ABS MTR1 and MTR2 Relay		By controlled by the skid control ECU assembly, supply power to the pump motor. Under the normal condition, the No. 1 skid control relay is used. When a malfunction is detected in the No. 1 skid control relay, the No. 2 skid control relay is used instead.
Skid Control ECU Assembly		Monitors the driving conditions of the vehicle in accordance with the signals received from the sensors, and through cooperative control with each ECU, calculates the required amount of braking force, and controls the brake actuator assembly.
Power Steering ECU Assembly		Controls the steering assist torque based on the signals received from the skid control ECU assembly.
Absorber Control ECU*2		Controls the damping force based on the signals received from the skid control ECU assembly.
Driving Support ECU Assembly*1		Makes a request for brake control to the skid control ECU assembly.
Network Gateway ECU1, 2		Transmits data between the CAN V bus and CAN sub bus 2.
Hybrid Vehicle Control ECU Assembly		Actuates regenerative braking upon receiving a signal from the skid control ECU assembly. Sends the actual regenerative braking control value to the skid control ECU assembly. Controls the drive force based on an output control request signal received from the skid control ECU assembly while the VSC or TRC is operating.
Main Body ECU (Multiplex Network Body ECU)		Detects the parking brake signal and outputs it to the skid control ECU assembly via CAN communication.
ECM		Performs engine output control based on the signal from the hybrid vehicle control ECU assembly.

*1: Models with pre-crash safety system

*2: Models with adaptive variable suspension system

SYSTEM CONTROL

Control	Function
Electronically Controlled Brake System	The electronically controlled brake system detects the amount that the brake pedal is depressed based on signals from the brake pedal stroke sensor assembly. The system uses the skid control ECU assembly to adjust the pressure supplied from the hydraulic pressure source for each wheel, generating optimal braking force.
Regenerative Braking Cooperative Control	This control performs cooperative control with regenerative braking that is specific to hybrid vehicles to efficiently charge the HV battery.
Anti-lock Brake System (ABS)	The ABS helps prevent the wheels from locking when the brakes are applied firmly or when braking on a slippery surface.
Electronic Brake Force Distribution (EBD)	The EBD utilizes ABS, achieving proper brake force distribution between the front and rear wheels in accordance with the driving conditions. In addition, during braking while cornering, the EBD also controls the brake forces of the right and left wheels, helping maintain vehicle behavior.
Brake Assist	The primary purpose of brake assist is to provide an auxiliary brake force to assist a driver who cannot generate a large brake force during emergency braking, thus helping ensure the vehicle's braking performance.
Traction Control (TRC)	The TRC helps restrain the slippage of the drive wheels if the driver depresses the accelerator pedal excessively when starting off or while accelerating on a slippery surface.
Vehicle Stability Control (VSC)	The VSC helps restrain sideways slippage of the vehicle during a strong front wheel skid or strong rear wheel skid, which may occur while cornering.
VSC and Cooperative Control with EPS1 or VSC+2	Effects cooperative control with the power steering ECU assembly in order to provide steering assist in accordance with the operating conditions of the vehicle.
Hill-start Assist Control	When starting uphill, this control maintains the brake hydraulic pressure to the 4 wheels, in order to momentarily prevent the vehicle from descending backward.
Radar Cruise Control Brake*3	When the driving support ECU assembly determines that a large deceleration is required based on the distance to the preceding vehicle and the relative vehicle speed during the dynamic radar cruise control system operation, the skid control ECU assembly operates the brake system according to the signal from the driving support ECU assembly.
Pre-crash Brake*3	When the driving support ECU assembly determines that the possibility of a collision is high or an unavoidable collision condition exists, the skid control ECU assembly activates the pre-crash brake assist or the pre-crash brake according to the signal from the driving support ECU assembly.
Motive Force Control during TRC or VSC Operation	Transmits a motive force control signal from the skid control ECU assembly to the hybrid vehicle control ECU assembly to limit the motive force while the TRC or VSC is being activated.
Emergency Brake Signal	In the case of emergency braking, emergency stop light control flashes the stop lights to alert the drivers in following vehicles.

*1: Models for general countries

*2: Models for Europe

*3: Models with pre-crash safety system

FAIL-SAFE

If a failure occurs in the skid control ECU assembly, sensors or brake actuator assembly, the system continues effecting brake control by excluding the failed area and using only the areas that are operating normally.
If the regenerative brake becomes unusable due to a failure in communication with the hybrid vehicle control ECU assembly, the skid control ECU assembly uses the hydraulic brake force to control the entire braking force.

DIAGNOSIS

If the skid control ECU assembly detects a malfunction in the brake control system, the warning lights illuminate and a warning message is displayed on the multi-information display. At the same time, a Diagnostic Trouble Code (DTC) is stored in the memory of the skid control ECU assembly.
If the skid control ECU assembly detects a malfunction during a sensor signal check (test mode), it stores the DTCs in its memory.
For details of DTCs and the check function, refer to the Repair Manual.