Lexus ES300 (2002 year). Manual — part 18

171

10A
ECU–IG

From Power Source System (See Page 56)

2L

6

C

5

C

7

2

P–

B

B–

R

B–

R

B–

R

B–

R

W

BZ

IG1

1

B

u

zze

r

Skid Control ECU

S 5(A), S 6(B), S 7(C), S 8(D)

2G

11

2P

7

1

R–

W

R–

W

PKB

C

21

* 1 : w/ Headlight Beam Level Control System
* 2 : w/ Electric Modulated Suspension System

Pa

rk

in

g

Br

a

k

e

SW

P 5

3B

68

3B

28

3B

29

3B

27

C

24

P

+BO

SS1+

P

18 B

B

27

V

SS1–

TRIG

Y–

R

6 B

R–

B

WA

C

1

L–

O

SP1

C

2

R–

W

LBLO

C

8

L

WT

C

4

R–

L

VSCW

C

14

LG

IND

C

6

BAT

SS1+

SS1–

TRIG

IG

9

3

11

10

1

B

B

C

13

GR

–

R

FRO

GR

–

R

(*1

)(

*1

)

26

H

e

ad

ligh

t B

e

a

m

Le

ve

l C

o

n

tr

o

l E

C

U

H1

4

SPDR

IF2

18

GR

HARD

B

25

(*2

)

GR

(*2

)

10

HARD

Ab

s

o

rb

e

r

Co

n

tr

o

l E

C

U

A2

1

W–

B

ESS

2

A

A

A

IB

1

4

T

R

AC

O

ff

SW

T 7

LG

CSW

B

7

3B

70

3B

30

W–

B

SB

Junction
Connector

J 4

Junction
Connector

J 1

VSC

Wa

rn

in

g

Bu

z

z

e

r

V1

1

Junction
Connector

J 2

Steering Sensor

S 9

R–B

L–O

R–W

L

R–L

W–

B

W

–

B

LG

2R

8

2L

8

W–

B

IA

172

VSC

3B

85

3B

84

3B

74

3B

75

A

40

A

39

A

6

A

32

B

17

3B

86

3B

96

3A

57

3A

87

A

21

B

14

B

13

B

20

R–B

L–O

R–W

L

R–L

LG

W

W

R–

W

W

L

R–

L

LG

BR

10A
GAUGE1

From Power Source System (See Page 56)

2M

1

2G

8

2O

5

7 1C

10A
IG2

W

W

WB

–

O

Combination Meter

C 7(A), C 8(B)

Sl

ip

VSC

TR

A

C

O

F

F

ABS

BR

AKE

Micro Computer

Power

ID

BR

173

1. ABS Operation

If the brake pedal is depressed suddenly, the ABS controls the hydraulic pressure of the wheel cylinders for all the four
wheels to automatically avoid wheel locking and ensure the directional and steering stability of the vehicle. If the brake pedal
is depressed suddenly, the skid control ECU controls the solenoids in the actuators using the signals from the sensors to
move the brake fluid to the reservoir in order to release the braking pressure applied to the wheel cylinder. If the skid control
ECU detects that the fluid pressure in the wheel cylinder is insufficient, the ECU controls the solenoids in the actuators to
increase the braking pressure.

2. Traction Control Operation

The traction control system controls the engine torque, the hydraulic pressure of the driving wheel cylinders, slipping of the
wheels which may occur at start or acceleration of the vehicle, to ensure an optimal driving power and vehicle stability
corresponding to the road conditions.

3. VSC Operation

Unexpected road conditions, vehicle speed, emergency situation, and any other external factors may cause large under– or
over–steering of the vehicle. If this occurs, the VSC system automatically controls the engine power and wheel brakes to
reduce the under– or over–steering.
To reduce large over–steering :
If the VSC system determines that the over–steering is large, it activates the brakes for the outer turning wheels depending
on the degree of the over–steering to produce the moment toward the outside of the vehicle and reduce the over–steering.
To reduce large under–steering :
If the VSC system determines that the under–steering is large, it controls the engine power and activates the rear wheel
brakes to reduce the under–steering.
TRAC off SW
The traction control SW is used to stop the TRAC function. After the engine is started, the TRAC system is stopped (turned
off) and the TRAC OFF indicator light lights up. When the TRAC off SW is pressed again, the TRAC system enters the
stand–by mode. If the engine is stopped and restarted, the TRAC system enters the stand–by mode regardless of the
traction control SW.
VSC system cannot cut off by using TRAC off SW.

4. Mutual System Control

To efficiently operate the VSC system at its optimal level, the VSC system and other control systems are mutually controlled
while the VSC system is being operated.
Engine throttle control
The engine power does not interfere with the VSC brake control by controlling the opening of the throttle and reducing the
engine output.
Engine control and electronically controlled transmission control
The strong braking force does not interfere with the braking force control of the VSC system by turning off the accel. and
reducing changes in the driving torque at shift–down.
VSC system operation indication
The Slip indicator light flashes and the buzzer sounds intermittently to warn the driver that the current road is slippery, while
the VSC system is being operated.

5. Fail Safe Function

If an error occurs in the skid control ECU, sensor signals, and/or actuators, the skid control ECU inhibits the brake actuator
control and inputs the error signal to the engine control module. According to the error signal, the brake actuator turns off the
solenoid and the engine control module rejects any electronically controlled throttle open request from the VSC system. As a
result, the vehicle functions regardless of the ABS, TRAC, and VSC systems.

S5 (A), S7 (C), S8 (D) Skid Control ECU

(C) 7–Ground : Approx. 12 volts with ignition SW at ON or ST position
(D)22–Ground : Always approx. 12 volts
(A) 15, (A) 22, (D) 2, (D) 3–Ground : Always continuity

System Outline

Service Hints

174

VSC

: Parts Location

Code

See Page

Code

See Page

Code

See Page

A4

36

D2

38

S6

B

39

A5

36

E6

38

S7

C

39

A6

36

H14

39

S8

D

39

A7

36

J1

39

S9

39

A21

38

J2

39

S13

39

A36

40

J3

39

T7

39

A37

40

J4

39

V11

39

B1

36

J6

A

39

Y1

39

C7

A

38

P5

39

C8

B

38

S5

A

39

: Relay Blocks

Code

See Page

Relay Blocks (Relay Block Location)

2

23

ABS R/B (Behind the Headlight LH)

: Junction Block and Wire Harness Connector

Code

See Page

Junction Block and Wire Harness (Connector Location)

1C

1E

25

Engine Room Main Wire and Engine Room J/B (Engine Compartment Left)

1G

g

g

(

g

)

2B

28

Instrument Panel Wire and Driver Side J/B (Lower Finish Panel)

2G

28

Engine Room Main Wire and Driver Side J/B (Lower Finish Panel)

2L

2M

2O

29

Instrument Panel Wire and Driver Side J/B (Lower Finish Panel)

2P

(

)

2R

3A

34 (w/ VSC)

Instrument Panel Wire and Passenger Side J/B (Instrument Panel Brace RH)

3B

34 (w/ VSC)

Instrument Panel Wire and Passenger Side J/B (Instrument Panel Brace RH)

: Connector Joining Wire Harness and Wire Harness

Code

See Page

Joining Wire Harness and Wire Harness (Connector Location)

IA3

46

Instrument Panel Wire and Floor No.1 Wire (Left Kick Panel)

IF2

46

Engine Room Main Wire and Instrument Panel Wire (Right Side of Steering Column Tube)

IF4

46

Engine Room Main Wire and Instrument Panel Wire (Right Side of Steering Column Tube)

IL1

48

Engine Wire and Instrument Panel Wire (Behind the Glove Box)

IL2

48

Engine Wire and Instrument Panel Wire (Behind the Glove Box)

IO5

48

Instrument Panel Wire and Floor No.2 Wire (Right Kick Panel)

: Ground Points

Code

See Page

Ground Points Location

EA

44

Right Fender

EB

44

Right Fender

ED

44

Left Fender

IA

46

Instrument Panel Reinforcement LH

IB

46

Instrument Panel Brace LH

ID

46

Instrument Panel Brace RH

: Splice Points

Code

See Page

Wire Harness with Splice Points

Code

See Page

Wire Harness with Splice Points

E1

44

Engine Room Main Wire