Lexus SC300 / Lexus SC400. Manual - part 959

137

B–R

R

G–W

LG–R

W

L–Y

B–Y

V–R

P–G

P–L

LG–B

LG

GR

L

R–B

R–W

TRACTION ECU

E 9

, E1 0

A

B

I33

I36

I36

2

IK2

15

EB1

5

1B

5

3A

6

B

11

IND

B

14

WT

B

8

BAT

B

2

STP

A

16

TR5

A

2

IG

A

15

BM

A

21

TR2

A

6

NEO

A

8

VTH

A

19

VSH

A

4

TRCO

A

5

THFA

A

4

W

A

37

TR

A

38

NEO

A

40

VT01

A

39

VT02

B

6

TC

B

1

BRC

B

4

BRFA

B

10

FRO

B

3

FLO

B

7

P

B

16

N

B

15

ABSO

B

5

RLO

A

1

PKB

C

13

RRO

C

4

RLO

C

14

TRCO

1E

11

3B

3

IJ2

12

IK2

4

IJ2

7

IK1

12

IK1

13

A

23

BRP

L–

R

L–

Y

Y–

R

P–

L

V–

Y

Y–

L

L–

Y

W

LG

–

R

B–

R

R

G–

W

L–

R

Y–

R

P–

L

V–

Y

Y–

L

P

R–

W

B–

Y

V–

R

P–

G

P–

L

LG

–B

LG

GR

L

R–

B

R–

W

P

R–

W

L–Y

R

L–

R

GR

L

G–R

L

Y–B

LG–R

G–W

B–R

R

R

FROM POWER SOURCE SYSTEM (SEE PAGE 56)

7. 5A
TRAC

GR

L

FROM A/T INDICATOR SW

ENGINE AND ECT ECU

T13

, T 14

B

A

13

14

I33

A

6

STP

G–

W

G–W

B

12

RRO

P–B

P–B

IK2

13

3H

7

3F

2

R–

W

R–

W

138

ABS AND TRACTION CONTROL

* 1 : USA SPEC.

B

41

VC

B

43

VTA

B

64

IDL

B

46

THG

B

63

IDL2

B

44

THW

B

69

E1

A

26

BCM

A

25

B

A

24

B

A

11

A

A

12

A

A

13

ACM

A

14

GND

A

20

E1

B

13

CSW

A

10

IDL1

A

22

IDL2

1

2

3

4

VC

VTA

IDL

E2

1

2

3

4

VC

VTA

IDL

E2

E18

I32

E18

I37

I32

6

2

IF

IJ

ED

3H

14

1E

18

3A

1

1J

1

2

1

3

6

4

5

BR

L–R

R

R–B

BR

BR

BR

G

R–

B

R

Y

L–

R

R–

B

R

BR

BR

R–

B

Y–

L

BR

R

Y

L–R

Y

R

L

W

G

BR

W–

B

BR

W–

B

BR

W–

B

W–

B

W–

B

B+

B–

B

A

A–

A+

L–R

TO

A

IR

F

L

O

W

ME

T

E

R

(VC

)

FR

O

M

A

IR

F

L

O

W

ME

T

E

R

(E2

)

THROTTLE POSITION
SENSOR

SUB THROTTLE POSITION
SENSOR

IK2

16

Y–

R

Y–

R

SUB THROTTLE ACTUATOR

TRACTION
CUT SW

TRACTION ECU

T12

S 8

T13

, T 1 4

A

B

S 9

T 2

ENGINE AND ECT ECU

E 9

, E 10

B

A

IJ1

13

W–

B

(SH

IEL

D

ED

)

E20

B

65

E2

BR

I32

B

42

VTA2

Y–

L

BR

1

2

1

2

BR

E3

EG

R

G

A

S

T

E

M

P

SE

N

SO

R

E

F

I

W

AT

ER

T

EM

P.

SEN

SO

R

A

3

S1

BR

(*1

)

(*1

)

E2

–

–

139

(FOR ABS)

THIS SYSTEM CONTROLS THE RESPECTIVE BRAKE FLUID PRESSURES ACTING ON THE DISC BRAKE CYLINDERS OF THE RIGHT
FRONT WHEEL, LEFT FRONT WHEEL AND REAR WHEELS WHEN THE BRAKES ARE APPLIED IN A PANIC STOP SO THAT THE
WHEELS DO NOT LOCK. THIS RESULTS IN IMPROVED DIRECTIONALLY STABILITY AND STEERABILITY DURING PANIC BRAKING.

1. INPUT SIGNALS

(1) SPEED SENSOR SIGNAL

THE SPEED OF THE WHEELS IS DETECTED AND INPUT TO TERMINALS FL+, FR+, RL+ AND RR+ OF THE ABS AND TRACTION
ECU.

(2) STOP LIGHT SW SIGNAL

A SIGNAL IS INPUT TO TERMINAL STP OF THE ABS AND TRACTION ECU WHEN THE BRAKE PEDAL IS OPERATED.

(3) PARKING BRAKE SW SIGNAL

A SIGNAL IS INPUT TO TERMINAL PKB OF THE ABS AND TRACTION ECU WHEN THE PARKING BRAKE IS OPERATED.

2. SYSTEM OPERATION

DURING SUDDEN BRAKING, THE ABS AND TRACTION ECU WHICH HAS SIGNALS INPUT FROM EACH SENSOR CONTROLS THE
CURRENT FLOWING TO THE SOLENOID INSIDE THE ACTUATOR AND LETS THE HYDRAULIC PRESSURE ACTING ON EACH WHEEL
CYLINDER ESCAPE TO THE RESERVOIR. THE PUMP INSIDE THE ACTUATOR IS ALSO OPERATING AT THIS TIME AND IT RETURNS
THE BRAKE FLUID FROM THE RESERVOIR TO THE MASTER CYLINDER, THUS PREVENTING LOCKING OF THE VEHICLE WHEELS.

IF THE ECU JUDGES THAT THE HYDRAULIC PRESSURE ACTING ON THE WHEEL CYLINDER IS INSUFFICIENT, THE CURRENT
ACTING ON SOLENOID IS CONTROLLED AND THE HYDRAULIC PRESSURE IS INCREASED, HOLDING OF THE HYDRAULIC
PRESSURE IS ALSO CONTROLLED BY THE COMPUTER, BY THE SAME METHOD AS ABOVE. BY REPEATED PRESSURE REDUCTION,
HOLDING AND INCREASE ARE REPEATED TO MAINTAIN VEHICLE STABILITY AND TO IMPROVE STEERABILITY DURING SUDDEN
BRAKING.

(FOR TRACTION CONTROL)

THE TRACTION CONTROL SYSTEM IS A SYSTEM WHEREBY THE “ABS AND TRACTION ECU” AND “TRACTION ECU” CONTROLS THE
ENGINE TORQUE AND THE HYDRAULIC PRESSURE OF THE WHEEL CYLINDER OF THE DRIVING WHEELS IN ORDER TO CONTROL
SPINNING OF THE DRIVING WHEELS WHEN STARTING OFF AND ACCELERATING, AND PROVIDE THE MOST APPROPRIATE DRIVING
FORCE IN RESPONSE TO THE ROAD CONDITIONS FOR VEHICLE STABILITY.

TRACTION CONTROL OPERATION

VEHICLE SPEED SIGNALS FROM THE SPEED SENSOR INSTALLED ON EACH WHEEL ARE INPUT TO THE ABS AND TRACTION ECU.

WHEN THE ACCELERATOR PEDAL IS DEPRESSED WHILE DRIVING ON A SLIPPERY ROAD AND THE DRIVING WHEEL (REAR WHEEL)
SLIPS, IF THE ROTATION OF THE REAR WHEEL EXCEEDS THE ROTATION OF THE FRONT WHEELS FOR A SPECIFIED PERIOD, THE
ECU JUDGES THAT THE REAR WHEEL IS SLIPPING.

WHEN THIS OCCURS, CURRENT FLOWS FROM TRACTION ECU TO SUB THROTTLE ACTUATOR TO CLOSE THE SUB THROTTLE
VALVE. THE THROTTLE VALVE OPENING ANGLE SIGNAL IS OUTPUT FROM TERMINAL VTA OF SUB THROTTLE POSITION SENSOR
TO  TERMINAL VTA2 OF ENGINE AND ECT ECU TO KEEP THE ENGINE RPM AT THE MOST SUITABLE LEVEL FOR THE DRIVING
CONDITIONS AND REDUCE SLIP OF THE DRIVING WHEEL. AT THE SAME TIME, OPERATION OF THE ABS AND TRACTION ECU
CAUSE THE TRACTION BRAKE ACTUATORS (ACC CUT, M/C CUT, RESERVOIR CUT SOLENOID) TO TURN ON TO SWITCH THE
HYDRAULIC CIRCUIT TO “TRACTION” MODE.

IN THIS CASE, SIGNALS ARE INPUT FROM TERMINAL SRR OF ABS AND TRACTION ECU TO TERMINAL (B)6 OF ABS ACTUATOR, AND
FROM  TERMINAL SRL OF ABS AND TRACTION ECU TO TERMINAL (B)1 OF ABS ACTUATOR, CONTROLLING THE REAR WHEEL
SOLENOID IN THE ABS ACTUATOR AND INCREASING THE HYDRAULIC PRESSURE OF THE WHEEL CYLINDER IN ORDER TO
PREVENT SLIP.

TO MAINTAIN THE HYDRAULIC PRESSURE OF THE REAR WHEELS, THE REAR WHEEL SOLENOID INSIDE THE ABS ACTUATOR IS
PUT IN “HOLD” MODE AND KEEPS THE HYDRAULIC PRESSURE TO THE BRAKE CYLINDER CONSTANT.

WHEN THE BRAKE CYLINDER HYDRAULIC PRESSURE IS REDUCED, THE PRESSURE REDUCTION MODE REDUCES AND CONTROLS
THE HYDRAULIC PRESSURE.

SYSTEM OUTLINE

140

ABS AND TRACTION CONTROL

A24

(A)

, A25

(B)

, A26

(C)  ABS AND TRACTION ECU

(B)21–GROUND

: ALWAYS APPROX. 12 VOLTS

(B)11–GROUND

: APPROX. 12 VOLTS WITH IGNITION SW AT ON POSITION

(B)10–GROUND

: CONTINUITY WITH STOP LIGHT SW ON

(B)2, (B)13, (B)22–GROUND : ALWAYS CONTINUITY
(B)17–GROUND

: CONTINUITY WITH PARKING BRAKE LEVER PULLED UP (PARKING BRAKE SW ON)

A 4

(B)

, A 5

(C)

, A 6

(A)  ABS ACTUATOR

(A)1, (A)2–GROUND : APPROX. APPROX. 12 VOLTS
(C)1–GROUND

: ALWAYS CONTINUITY

(B)1, (B)5, (B)4, (B)6–GROUND : APPROX. 1.15



 (IGNITION SW OFF)

(B)2–GROUND

: APPROX. 5



 (IGNITION SW OFF)

T 3

(A)

, T 4

(B)

 

 TRACTION BRAKE ACTUATOR

(B)2– (B)4

: OPEN ABOVE APPROX. 134.5KG/CM

2 

(13189KPA, 1910PSI)

CLOSED BELOW APPROX. 95KG/CM

2

 (9316KPA, 1349PSI)

(A)3– (A)6

: APPROX. 2



(A)2– (A)5

: APPROX. 2



(A)1– (A)4

: APPROX. 2



S12

  STOP LIGHT SW

2–1 : CLOSED WITH BRAKE PEDAL DEPRESSED

A 7, A 8, A30, A31

  ABS SPEED SENSOR FRONT LH, RH, REAR LH, RH

1–2 : APPROX. 1.0

 

(20

°

C, 68

°

F)

T13

(B)

, T14

(A)  TRACTION ECU

(A) 2–GROUND

: APPROX. 12 VOLTS WITH IGNITION SW AT ON POSITION

(A)15–GROUND

: ALWAYS APPROX. 12 VOLTS

(A)20, (A)14–GROUND : ALWAYS CONTINUITY
(A) 1–GROUND

: CONTINUITY WITH PARKING BRAKE LEVER PULLED UP

(B) 2–GROUND

: APPROX. 12 VOLTS WITH STOP LIGHT SW ON

(B)13–GROUND

: CONTINUITY WITH TRACTION CUT SW PUSHED ON

(B) 8–GROUND

: ALWAYS APPROX. 12 VOLTS

P 3

  PARKING BRAKE SW

1–GROUND : CLOSED WITH PARKING BRAKE LEVER PULLED UP

S 8

  SUB THROTTLE ACTUATOR

2–1, 2–3

: APPROX. 0.9



5–4, 5–6

: APPROX. 0.9



: PARTS LOCATION

CODE

SEE PAGE

CODE

SEE PAGE

CODE

SEE PAGE

A 4

B

26

C 3

26

S 9

27

A 5

C

26

C13

B

28

S12

29

A 6

A

26

C14

A

28

T 2

27

A 7

26

D 1

28

T 3

A

27

A 8

26

D 2

28

T 4

B

27

A10

26

E 2

26

T 5

27

A24

A

28

E 3

26

T 6

29

A25

B

28

E 9

A

28

T12

29

A26

C

28

E10

B

28

T13

B

29

A30

30

F 9

26

T14

A

29

A31

30

P 3

29

B 1

26

S 8

27

: RELAY BLOCKS

CODE

SEE PAGE

RELAY BLOCKS (RELAY BLOCK LOCATION)

2

19

ENGINE COMPARTMENT LEFT

6

24

ENGINE COMPARTMENT LEFT

SERVICE HINTS