Lexus ES300 (2002 year). Service manual — part 111

CHASSIS – BRAKE

CH-70

208CH32

Stop Light Switch

Speed Sensors

Steering Angle
Sensor

Yew Rate Sensor

Deceleration Sensor

Master Cylinder
Pressure Sensor

Skid Control

ECU

ECM

Brake Actuator

Slip Indicator Light

VSC Warning
Light

VSC Warning
Buzzer

TRAC not

TRAC Activated

Item

TRAC not

Activated

Increase

Mode

Holding

Mode

Reduction

Mode

(1), (6)

Master Cylinder Cut
Solenoid Valve

OFF

(Open)

ON*

ON*

ON*

(1), (6)

Port: (A), (F)

(Open)

ON

ON

ON

(3), (4)

Reservoir Cut
Solenoid Valve

OFF

(Close)

ON

(Open)

ON

(Open)

ON

(Open)

(3), (4)

Port: (C), (D)

(Close)

(Open)

(Open)

(Open)

(2) (5)

Suction Solenoid Valve

OFF

OFF

OFF

OFF

(2), (5)

Port: (B), (E)

OFF

(Close)

OFF

(Close)

OFF

(Close)

OFF

(Close)

(7) (10)

Pressure Holding Valve

OFF

OFF

ON

ON

(7), (10)

Port: (G), (J)

OFF

(Open)

OFF

(Open)

ON

(Close)

ON

(Close)

Front
Brake

(11),

(14)

Pressure Reduction
Valve

OFF

(Close)

OFF

(Close)

OFF

(Close)

ON

(Open)

Brake

(14)

Port: (K), (N)

(Close)

(Close)

(Close)

(Open)

Wheel Cylinder Pressure

—

Increase

Hold

Reduction

(8) (9)

Pressure Holding Valve

OFF

ON

ON

ON

(8), (9)

Port: (H), (J)

OFF

(Open)

ON

(Close)

ON

(Close)

ON

(Close)

Rear
Brake

(12),

(13)

Pressure Reduction
Valve

OFF

(Close)

OFF

(Close)

OFF

(Close)

OFF

(Close)

(13)

Port: (L), (M)

(Close)

(Close)

(Close)

(Close)

Wheel Cylinder Pressure

—

—

—

—

*: The solenoid valve controls the hydraulic pressure between “open” through “close” according to the

operating condition by adjusting continually.

VSC Operation

1) General

The VSC system, by way of solenoid valves, controls the fluid pressure that is generated by the pump
and applies it to the brake wheel cylinder of each wheel in the following 3 modes: pressure reduction,
pressure holding, and pressure increase modes. As a result, the tendency to understeer or oversteer is
restrained.

System Diagram

CHASSIS – BRAKE

CH-71

208CH33

Increase Mode

Master Cylinder

Master Cylinder
Pressure Sensor

Master Cylinder
Pressure Sensor

Port (A)

Port (B)

Port (C)

Port (D)

Port (E)

Port (F)

Port (G)

Port (H)

Port (I)

Port (J)

Port (K)

Port (L)

Port (M)

Port (N)

Pumps

Reservoirs

Front Left

Rear Right

Rear Left

Front Right

(1)

(2)

(3)

(4)

(5)

(6)

(7)

(8)

(9)

(10)

(11)

(12)

(13)

(14)

2) Understeer Restraining Control (Turning to the Right)

In understeer restraining control, the brake of the front wheels and rear wheel of the inner side of the turn
is applied.
Also, depending on whether the brake is ON or OFF and the condition of the vehicle, there are
circumstances in which the brake might not be applied to the wheels even if those wheels are targeted
for braking.
The diagram below shows the hydraulic circuit in the pressure increase mode, as it restrains an understeer
condition while the vehicle makes a right turn.
In other, the pressure holding valve and the pressure reduction valve are turned ON / OFF according to
the ABS operation pattern.

CHASSIS – BRAKE

CH-72

VSC not

VSC Activated

Item

VSC not

Activated

Increase

Mode

Holding

Mode

Reduction

Mode

(1), (6)

Master Cylinder Cut
Solenoid Valve

OFF

(Open)

ON*

ON*

ON*

(1), (6)

Port: (A), (F)

(Open)

ON

ON

ON

(3) (4)

Reservoir Cut Solenoid Valve

OFF

ON

ON

ON

(3), (4)

Port: (C), (D)

OFF

(Close)

ON

(Open)

ON

(Open)

ON

(Open)

(2) (5)

Suction Solenoid Valve

OFF

OFF

OFF

OFF

(2), (5)

Port: (B), (E)

OFF

(Close)

OFF

(Close)

OFF

(Close)

OFF

(Close)

(7),

Pressure Holding Valve

OFF

OFF

ON

ON

F

(7),

(10)

Port: (G), (J)

OFF

(Open)

OFF

(Open)

ON

(Close)

ON

(Close)

Front
Brake

(11),

Pressure Reduction Valve

OFF

OFF

OFF

ON

Brake

(11),

(14)

Port: (K), (N)

OFF

(Close)

OFF

(Close)

OFF

(Close)

ON

(Open)

Wheel Cylinder Pressure

—

Increase

Hold

Reduction

(8)

Pressure Holding Valve
(Rear Right)

OFF

(Open)

OFF

(Open)

ON

(Close)

ON

(Close)

(8)

Port: (H)

(Open)

(Open)

(Close)

(Close)

(9)

Pressure Holding Valve
(Rear Left)

OFF

(Open)

ON

(Close)

ON

(Close)

ON

(Close)

(9)

Port: (I)

(Open)

(Close)

(Close)

(Close)

Rear
Brake

(12)

Pressure Reduction
Valve (Rear Right)

OFF

(Close)

OFF

(Close)

OFF

(Close)

ON

(Open)

Brake

(12)

Port: (L)

(Close)

(Close)

(Close)

(Open)

(13)

Pressure Reduction
Valve (Rear Left)

OFF

(Close)

OFF

(Close)

OFF

(Close)

OFF

(Close)

(13)

Port: (M)

(Close)

(Close)

(Close)

(Close)

Wheel Cylinder Pressure

Right

—

Increase

Hold

Reduction

Wheel Cylinder Pressure

Left

—

—

—

—

*: The solenoid valve controls the hydraulic pressure between “open” through “close” according to the

operating condition by adjusting continually.

CHASSIS – BRAKE

CH-73

208CH34

Increase Mode

Master Cylinder

Master Cylinder
Pressure Sensor

Master Cylinder
Pressure Sensor

Port (A)

Port (B)

Port (C)

Port (D)

Port (E)

Port (F)

Port (G)

Port (H)

Port (I)

Port (J)

Port (K)

Port (L)

Port (M)

Port (N)

Pumps

Reservoirs

Front Left

Rear Right

Rear Left

Front Right

(1)

(2)

(3)

(4)

(5)

(6)

(7)

(8)

(9)

(10)

(11)

(12)

(13)

(14)

3) Oversteer Restraining Control (Turning to the Right)

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 make a right turn.
As in understeer restraining control, in other, the pressure holding valve and the pressure reduction valve
are turned ON / OFF according to the ABS operating 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.