Lexus ES300 (2002 year). Service manual - part 107

CHASSIS – BRAKE

CH-63

170CH07

Braking
Force

Braking
Force

Making a Right Turn

Oversteering
Control Moment

2) Dampening a Strong Oversteer

When the skid control ECU determines that
the vehicle exhibits a strong tendency to
oversteer, depending on the extent of that
tendency, it controls the engine output and
applies the brakes of the front and rear wheels
of the outside of the turn, thus generating an
inertial moment in the vehicle’s outward
direction, which helps dampen its tendency to
oversteer.

CHASSIS – BRAKE

CH-64

211CH31

TRAC OFF Indicator Light

VSC Warning Light

Slip Indicator Light

ABS Warning
Light

Brake System
Warning Light

Steering Angle Sensor

TRAC OFF Switch

VSC Warning Buzzer

Skid Control ECU

Brake Actuator

Front Speed Sensor

Yaw Rate & Deceleration Sensor

Rear Speed Sensors

Stop Light Switch

Front Speed Sensor

Solenoid Relay

Motor Relay

6. Layout of Component

CHASSIS – BRAKE

CH-65

Brake Actuator

7. Function of Component

Component

Function

ABS Warning Light

Lights up to alert the driver when the skid control ECU detects the
malfunction in the ABS or Brake Assist system.

VSC Warning Light

Lights up to alert the driver when the skid control ECU detects the
malfunction in the VSC system.

Combination

Slip Indicator Light

Blinks to inform the driver when the TRAC system or the VSC
system is operated.

Combination
Meter

TRAC OFF
Indicator Light

 Lights up to inform the driver when the TRAC system is turned

OFF by the TRAC OFF switch.

 Lights up to inform the driver when the skid control ECU

detects the malfunction in the TRAC or VSC system.

Brake System
Warning Light

Lights up together with the ABS warning light to alert the driver
when the skid control ECU detects the malfunction in the EBD
control.

ECM

 Sends the throttle valve opening angle signal, crankshaft

position sensor, intake air temp. sensor, etc., to the skid control
ECU.

 Receive the signal of throttle valve opening request from the

skid control ECU.

Speed Sensors

Detects the wheel speed of each four wheels.

Charges the fluid path based on the signals from the skid control
ECU during the operation of the ABS with EBD & Brake Assist
& TRAC & VSC system, in order to control the fluid pressure that
is applied to the wheel cylinders.

Master Cylinder
Pressure Sensor

Assembled in the brake actuator and detects the master cylinder
pressure.

Skid Control ECU

Judges the vehicle driving condition based on signals from each
sensor, and sends brake control signal to the brake actuator.

Brake Fluid Level Warning Switch

Detects the brake fluid level.

Stop Light Switch

Detects the brake pedal depressing signal.

TRAC OFF Switch

Turns the TRAC system inoperative.

VSC Warning Buzzer

Emits an intermittent sound to inform the driver that the skid
control ECU detects the strong understeer tendency or strong
oversteer tendency.

Yaw Rate

&

Deceleration Sensor

 Detects the vehicle’s yaw rate.

 Detects the vehicle’s acceleration in the forward, rearward,

lateral.

Steering Angle Sensor

Detects the steering direction and angle of the steering wheel.

Motor Relay

Supply power to the pump motor in the brake actuator.

Solenoid Relay

Supply power to the solenoid valves in the brake actuator.

CHASSIS – BRAKE

CH-53

208CH22

Speed Sensors

Speed Sensors

Brake Fluid Level
Warning Switch

Stop Light Switch

Brake
Actuator

Skid
Control
ECU

DLC3

Speedometer

ABS Warning Light

Brake System
Warning Light

Combination Meter

ABS with EBD System

1. General

 The primary purpose of the ABS has been to help the vehicle’s behavior during braking.
 The EBD control utilizes ABS, realizing the proper brake force distribution between front and rear wheels

in accordance with the driving conditions.
In addition, during cornering braking, it also controls the brake forces of right and left wheels, helping to
maintain the vehicle behavior.

2. System Diagram

3. Outline of EBD Control

General

The distribution of the brake force, which was performed mechanically in the past, is now performed under
electrical control of the skid control ECU, which precisely controls the braking force in accordance with
the vehicle’s driving conditions.