Lexus RX300 (MCU15). Service manual - part 56

CH

BO

CHASSIS — BRAKES

Mode

Solenoid Valves

97

" While the Vehicle Makes a Right Turn A

VSC Activated

VSC Not

Activated

Pressure

Increase

Mode

Pressure

Holding

Mode

Pressure

Reduction

Mode

(2)

Master Cylinder Cut Solenoid Valve
(Front Right)

OFF

ON

ON

ON

(2)

Port: (A)

Open

Close

Close

Close

(3)

Master Cylinder Cut Solenoid Valve
(Fornt Right, Rear Left)

OFF

OFF

OFF

OFF

(3)

Port: (B)

Open

Open

Open

Open

(6)

Master Cylinder Cut Solenoid Valve
(Front Left, Rear Right)

OFF

ON

ON

ON

(6)

Port: (E)

Open

Close

Close

Close

(7)

Master Cylinder Cut Solenoid Valve
(Front Left)

OFF

OFF

OFF

OFF

(7)

Port: (F)

Open

Open

Open

Open

(4)

Reservoir Cut
Solenoid Valve

OFF

ON

ON

ON

(5)

Port: (C), (D)

Close

Open

Open

Open

(8)

Pressure Holding Valve
(Front)

OFF

OFF

ON

ON

(11)

Port: (G), (J)

Open

Open

Close

Close

(9)

Pressure Holding Valve
(Rear Left)

OFF

OFF

OFF

OFF

(9)

Port: (H)

Open

Open

Open

Open

(10)

Pressure Holding Valve
(Rear Right)

OFF

OFF

ON

ON

(10)

Port: (I)

Open

Open

Close

Close

(12)

Pressure Reduction Valve
(Front)

OFF

OFF

OFF

ON

(15)

Port: (K), (N)

Close

Close

Close

Open

(13)

Pressure Reduction Valve
(Rear Left)

OFF

OFF

OFF

OFF

(13)

Port: (L)

Close

Close

Close

Close

(14)

Pressure Reduction Valve
(Rear Right)

OFF

OFF

OFF

ON

(14)

Port: (M)

Close

Close

Close

Open

Front Right wheel

—

Increase

Hold

Reduction

Wheel Cylinder

Front Left wheel

—

Increase

Hold

Reduction

Wheel Cylinder
Pressure

Rear Right wheel

—

Increase

Hold

Reduction

Rear Left wheel

—

—

—

—

CHASSIS — BRAKES

98

c. Oversteer Restraining Control

In oversteer restraining control, the brake of the front and rear wheels of the outer side of the turn
is applied. As an example, the diagram below shows the hydraulic circuit in the pressure increase mode,
as it restrains an oversteer condition while the vehicle makes a right turn.
As in understeer restraining control, in other operating modes, the pressure holding valve and the pres-
sure reduction valve are turned ON/OFF according to the ABS operation pattern.
However, in oversteer control, the pressure holding valve is turned ON and blocks the hydraulic passage
to the front inner wheel in order to prevent applying the brake to the front inner wheel.

Port (A)

Port (H)

Port (G)

Port (L)

Port (K)

Port (F)

Port (I)

Port (J)

Port (M)

Port (N)

Port (B)

Port (C)

Port (D)

Port (E)

Increase Mode

161ES38

Master
Cylinder

(1)

(1)

(2)

(3)

(1)

(4)

(5)

(6)

(7)

(1)

(8)

(9)

(12)

(13)

(14)

(15)

(10)

(11)

Front Right
Wheel Cylinder

Rear Left
Wheel Cylinder

Rear Right
Wheel Cylinder

Front Left
Wheel Cylinder

Reservoirs

Pumps

" System Diagram A

187CH42

Speed Sensor

Skid

Control

ECU

Engine ECU

Brake 

Actuator

Slip Indicator

Light

Stop Light

Switch

Steering Angle

Sensor

Yaw Rate

Sensor

Deceleration

Sensor

VSC Warning

Light

VSC Warning

Buzzer

CH

BO

CHASSIS — BRAKES

Mode

Solenoid Valves

99

" While the Vehicle Makes a Right Turn A

VSC Activated

VSC Not

Activated

Pressure

Increase

Mode

Pressure

Holding

Mode

Pressure

Reduction

Mode

(2)

Master Cylinder Cut Solenoid Valve
(Front Right)

OFF

OFF

OFF

OFF

(2)

Port: (A)

Open

Open

Open

Open

(3)

Master Cylinder Cut Solenoid Valve
(Front Right, Rear Left)

OFF

ON

ON

ON

(3)

Port: (B)

Open

Close

Close

Close

(6)

Master Cylinder Cut Solenoid Valve
(Front Left, Rear Right)

OFF

OFF

OFF

OFF

(6)

Port: (E)

Open

Open

Open

Open

(7)

Master Cylinder Cut Solenoid Valve
(Front Left)

OFF

ON

ON

ON

(7)

Port: (F)

Open

Close

Close

Close

(4)

Reservoir Cut
Solenoid Valve

OFF

ON

ON

ON

(5)

Port: (C), (D)

Close

Open

Open

Open

(8)

Pressure Holding Valve
(Front Right)

OFF

ON

ON

ON

(8)

Port: (G)

Open

Close

Close

Close

(11)

Pressure Holding Valve
(Front Left)

OFF

OFF

ON

ON

(11)

Port: (J)

Open

Open

Close

Close

(9)

Pressure Holding Valve
(Rear Left)

OFF

OFF

ON

ON

(9)

Port: (H)

Open

Open

Close

Close

(10)

Pressure Holding Valve
(Rear Right)

OFF

OFF

OFF

OFF

(10)

Port: (I)

Open

Open

Open

Open

(12)

Pressure Reduction Valve
(Front Right)

OFF

OFF

OFF

OFF

(12)

Port: (K)

Close

Close

Close

Close

(13)

Pressure Reduction Valve
(Rear Left)

OFF

OFF

OFF

ON

(13)

Port: (L)

Close

Close

Close

Open

(14)

Pressure Reduction Valve
(Rear Right)

OFF

OFF

OFF

OFF

(14)

Port: (M)

Close

Close

Close

Close

(15)

Pressure Reduction Valve
(Front Left)

OFF

OFF

OFF

ON

(15)

Port: (N)

Close

Close

Close

Open

Front Right wheel

—

—

—

—

Wheel Cylinder

Front Left wheel

—

Increase

Hold

Reduction

Wheel Cylinder
Pressure

Rear Right wheel

—

—

—

—

Rear Left wheel

—

Increase

Hold

Reduction

CHASSIS — BRAKES

100

6) Brake Assist Operation

The fluid pressure that has been generated by the pump in the brake actuator is directed to the wheel
cylinders.  By applying a greater fluid pressure than the master cylinder, a greater braking force is achieved.

Port (A)

Port (H)

Port (G)

Port (L)

Port (K)

Port (F)

Port (I)

Port (J)

Port (M)

Port (N)

Port (B)

Port (C)

Port (D)

Port (E)

187CH21

Master
Cylinder

(1)

(1)

(2)

(3)

(1)

(4)

(5)

(6)

(7)

(1)

(8)

(9)

(12)

(13)

(14)

(15)

(10)

(11)

Front Right
Wheel Cylinder

Rear Left
Wheel Cylinder

Rear Right
Wheel Cylinder

Front Left
Wheel Cylinder

Reservoirs

Pumps

" System Diagram A

187CH43

Speed Sensor

Skid

Control

ECU

Brake

Actuator

Stop Light

Switch

ABS Warning

Light

Master Cylinder

Pressure Sensor