Lexus SC300 / Lexus SC400. Manual - part 974

128

ECT AND A/T INDICATOR

PO

W

E

R

NO

R

M

A

L

3

4

7

1

5

2

9

1

2

IJ2

3

IK1

5

IK1

2

IK1

22

IJ1

6

IK1

21

IG2

7

1E

12

1K

4

3D

3

3D

6

3B

4

3B

5 3D

3A

4

3D

13

1H

12

B

76

NSW

A

18

P

A

9

2

A

10

L

A

2

SP1

B

17

TT

A

19

TE2

A

28

OD2

IK1

4

IK1

3

I19

A

14

IJ1

10

GR–Y

LG

G–O

G–O

Y

Y

G

W

G–O

GR–R

W–B

Y

Y

Y

ENG

TE1

TT

TE2

ECT

Y

Y

B–

W

B–

W

G–

O

G

W

P

P

P

P

G–

R

G–

Y

GR

–

R

GR

–

R

GR

–

Y

LG

G–

R

G–

Y

GR

–

R

W–

B

G

R

–

R

GR

–

R

G–

O

FROM POWER SOURCE SYSTEM (SEE PAGE 56)

5

7. 5A
ST

10A
GAUGE

ECT PATTERN
SELECT SW

ENGINE AND ECT ECU

O/

D

M

A

IN

SW

TDCL

E 8

E 9

, E1 0

T 6

O5

A

A

10

IH

BR

A

E20

IK1

6

IK1

7

2

2

A

13

A

15

SH

O

R

T

CO

N

NE

CT

O

R

L

–R

L–R

R

3

2

OUT

GND

L–R

R

1

VCC

SPEED SENSOR
NO. 1

S 3

Y

A

B

B

S2

2

A

,S

2

3

129

P

R

N

D

2

1

1

4

6

5

7

8

9

GR

R–

B

L

G–

W

G

W

A/T INDICATOR SW
[NEUTRAL START SW AND

BACK–UP LIGHT SW]

N 1

B

4

C

1

C

2

C

3

C

4

C

5

C

16

A

1

4

10

5

6

7

8

9

I33

I33

I19

I19

I19

I19

I22

I22

IK1

12

IK1

11

IK1

13

IK1

14

IK1

16

IK1

17

C

18

B

A

23

3D

10

3D

9

3H

3

3A

1

1J

1

1E

18

IF

Y

Y

G

W

G–O

GR–R

W–B

W–B

W–B

W–B

GR

–

R

Y

G

W

W

G

G–

W

L

R–

B

GR

G–

O

GR

R–

B

L

G–

W

G

W

Y

GR

R–

B

L

G–

W

G

W

W–

B

W–

B

A/T INDICATOR LIGHT
[COMB. METER]

EC

T

P

O

W

ER

P

R

N

D

2

L

O/

D

OF

F

A/T INDICATOR LIGHT
(FOR SHIFT LEVER)

A21

C12

, C13

, C14 A

W–B

C

P

R

N

D

2

L

W

G

G–W

L

R–B

GR

C

17

3H

1

3A

9

T

O

P

A

NE

L

F

US

E

(US

A

)

TO

IN

TE

G

R

A

TI

O

N

R

E

L

A

Y

(CA

NA

DA

)

1

G–

O

3C

1

G–O

G–O

G–

O

G–

O

G–

O

130

ECT AND A/T INDICATOR

THIS SYSTEM, ELECTRICALLY CONTROLS THE LINE PRESSURE, THROTTLE PRESSURE, LOCK–UP PRESSURE AND ACCUMULATOR
PRESSURE ETC. THROUGH THE SOLENOID VALVE. THE ECT IS A SYSTEM WHICH PRECISELY CONTROLS GEAR SHIFT TIMING AND
LOCK–UP TIMING IN RESPONSE TO THE VEHICLE’S DRIVING CONDITIONS AND THE ENGINE OPERATING CONDITIONS DETECTED
BY VARIOUS SENSORS, MAKING SMOOTH DRIVING POSSIBLE BY SHIFT SELECTION FOR EACH GEAR WHICH IS THE MOST
APPROPRIATE TO THE DRIVING CONDITIONS AT THAT TIME, AND CONTROLS THE ENGINE TORQUE DURING SHIFTING TO ACHIEVE
OPTIMUM SHIFT FEELING.

1. GEAR SHIFT OPERATION

WHEN DRIVING, THE ENGINE WARM UP CONDITION IS INPUT AS A SIGNAL TO TERMINAL (B)44 OF THE ECU FROM THE EFI WATER
TEMP. SENSOR AND THE VEHICLE SPEED SIGNAL FROM SPEED SENSOR NO.2 IS INPUT TO TERMINAL (B)23 OF THE ECU. AT THE
SAME TIME, THE THROTTLE VALVE OPENING SIGNAL FROM THE THROTTLE POSITION SENSOR (MAIN) IS INPUT TO TERMINAL
(B)43 OF THE ECU AS ENGINE RPM CONDITION (IDLING, HIGH LOAD AND ACCELERATION CONDITIONS) SIGNAL.

BASED ON THESE SIGNALS, THE ECU SELECTS THE BEST SHIFT POSITION FOR DRIVING CONDITIONS AND SENDS CURRENT TO
THE ECT SOLENOIDS.

WHEN SHIFTING TO 1ST SPEED, THE CURRENT FLOWS FROM TERMINAL (B)10 OF THE ECU 

→

 TERMINAL 1 OF ECT SOLENOIDS 

→

GROUND AND CONTINUITY TO NO.1 SOLENOID CAUSES THE SHIFT (NO.2 SOLENOID DOES NOT HAVE CONTINUITY AT THIS TIME).

FOR 2ND SPEED, THE CURRENT FLOWS SIMULTANEOUSLY FROM TERMINAL (B)9 OF THE ECU 

→

 TERMINAL 2 OF ECT SOLENOIDS

→

 GROUND, AND FROM TERMINAL (B)10 OF THE ECU 

→

 TERMINAL 1 OF ECT SOLENOIDS 

→

 GROUND, AND CONTINUITY TO NO.1

AND NO.2 SOLENOIDS CAUSES THE SHIFT.

FOR 3RD SPEED, THERE IS NO CONTINUITY TO NO.1 SOLENOID, ONLY TO NO.2 SOLENOID, CAUSING THE SHIFT.

SHIFTING INTO THE 4TH SPEED (OVERDRIVE) OCCURS WHEN NO CURRENT FLOWS TO NO.1 AND NO.2 SOLENOIDS. THE NO.4
SOLENOID (FOR ACCUMULATOR BACK PRESSURE MODULATION) IS INSTALLED TO ADJUST THE BACK PRESSURE ON THE
ACCUMULATOR AND CONTROL THE HYDRAULIC PRESSURE DURING SHIFTING AND LOCK–UP IN ORDER TO PROVIDE SMOOTH
SHIFTING WITH LITTLE SHIFT SHOCK.

2. LOCK–UP OPERATION

WHEN THE ECT ECU DECIDES, BASED ON EACH SIGNAL, THAT THE LOCK–UP CONDITION HAS BEEN MET, THE CURRENT FLOWS
FROM 

→

 TERMINAL (B)8 OF THE ECU 

→

 TERMINAL 3 OF THE ECT SOLENOID 

→

 GROUND, CAUSING CONTINUITY TO THE LOCK–UP

SOLENOID AND CAUSING LOCK–UP OPERATION.

3. STOP LIGHT SW CIRCUIT

IF THE BRAKE PEDAL IS DEPRESSED (STOP LIGHT SW ON) WHEN DRIVING IN LOCK–UP CONDITION, A SIGNAL IS INPUT TO
TERMINAL (A)4 OF THE ECU.  THE ECU OPERATES AND CUTS THE CURRENT TO THE SOLENOID TO RELEASE LOCK–UP.

4. OVERDRIVE CIRCUIT

* O/D MAIN SW ON

WHEN THE O/D MAIN SW IS TURNED ON (SW POINT IS OPEN), A SIGNAL IS INPUT TO TERMINAL (A)28 OF THE ECU AND THE ECT
CAUSES SHIFT TO OVERDRIVE WHEN THE CONDITIONS FOR OVERDRIVE ARE MET.

* O/D MAIN SW OFF

WHEN THE O/D MAIN SW IS TURNED OFF (SW POINT IS CLOSED), THE CURRENT FLOWING THROUGH THE O/D OFF INDICATOR
LIGHT FLOWS TO GROUND BY WAY OF THE O/D MAIN SW AND CAUSES THE O/D OFF INDICATOR LIGHT TO LIGHT UP. AT THE
SAME TIME, A SIGNAL IS INPUT TO TERMINAL (A)28 OF THE ECU AND THE ECT PREVENTS SHIFT INTO OVERDRIVE.

5. ECT PATTERN SELECT SW CIRCUIT

WHEN THE ECT PATTERN SELECT SW IS CHANGED FROM “NORMAL” TO “POWER”, THE CURRENT THROUGH THE GAUGE FUSE
FLOWS TO TERMINAL 4 OF ECT PATTERN SELECT SW 

→

 TERMINAL 3 

→

 TERMINAL (B)4 OF A/T INDICATOR 

→

 TERMINAL (C)23 

→

GROUND AND CAUSES THE INDICATOR LIGHT TO LIGHT UP. AT THE SAME TIME, THE CURRENT FLOWS TO TERMINAL (A)18 OF
THE ECU AND THE ECU PERFORMS SHIFT UP AND SHIFT DOWN AT A HIGHER VEHICLE SPEED RANGE COMPARED WITH
“NORMAL” POSITION.

6. KICK DOWN OPERATION

WHEN THE ACCELERATOR IS DEPRESSED FURTHER THAN THE FULL THROTTLE POSITION WHILE DRIVING, THE KICK DOWN SW
TURNS ON AND ITS SIGNAL IS INPUT TO TERMINAL (A)3 OF THE ECU. THEN, THE ECU CONTROLS THE CURRENT WHICH FLOWS
FROM  TERMINALS (B)10 AND (B)9 OF THE ECU TO THE NO. 1 AND NO. 2 SOLENOIDS AND SHIFTS DOWN BY TURNING THE
SOLENOIDS ON AND OFF.

7. CRUISE CONTROL

WHEN CRUISE CONTROL OPERATION IS SELECTED A SIGNAL IS INPUT TO TERMINAL (A)12 OF THE ECU FROM CRUISE CONTROL
ECU. AS A RESULT, THE ECU OPERATES AND CONTROLS OVERDRIVE, LOCK–UP AND SO ON FOR SMOOTH DRIVING.

SYSTEM OUTLINE

131

E 1

  ECT SOLENOID

1–4 :  APPROX. 5.3

2–5 :  APPROX. 3.7

3–GROUND : APPROX. 13.2

6–GROUND : APPROX. 13.2

E 2

  EFI WATER TEMP. SENSOR

1–2 : APPROX. 16.2K

 

(–20

°

C –4

°

F)

APPROX.   2.5K

 

(20

°

C 68

°

F)

APPROX. 0.32K

 

(80

°

C 176

°

F)

E 8

  ECT PATTERN SELECT SW

4–3 :  CLOSED WITH ECT PATTERN SELECT SW AT POWER POSITION

E 9

(A), 

E10

(B)  ENGINE AND ECT ECU

BATT – E1:

ALWAYS APPROX. 12 VOLTS

IGSW – E1:

APPROX. 12 VOLTS WITH IGNITION SW ON

BK

– E1:

APPROX. 12 VOLTS WITH BRAKE PEDAL DEPRESSED

P

– E1:

APPROX. 12 VOLTS WITH IGNITION SW ON POSITION AND ECT PATTERN SELECT SW AT POWER POSITION

KD–GROUND :CONTINUITY WITH KICK DOWN SW ON
OD2

– E1:

APPROX. 12 VOLTS WITH O/D MAIN SW ON
                0 VOLTS WITH O/D MAIN SW ON

+B–GROUND

: APPROX. 12 VOLTS WITH IGNITION SW AT ON POSITION

+B1–GROUND : APPROX. 12 VOLTS WITH IGNITION SW AT ON POSITION
MREL–GROUND:APPROX. 12 VOLTS WITH IGNITION SW AT ON POSITION
E01–GROUND : ALWAYS CONTINUITY
E02–GROUND : ALWAYS CONTINUITY
L–GROUND

: APPROX. 12 VOLTS WITH SHIFT LEVER AT “L” RANGE

2–GROUND

: APPROX. 12 VOLTS WITH SHIFT LEVER AT “2” RANGE

R–GROUND

: APPROX. 12 VOLTS WITH SHIFT LEVER AT “R” RANGE

E1–GROUND

: ALWAYS CONTINUITY

VC–VTA1

: LESS THAN 1 VOLTS WITH THROTTLE VALVE FULLY CLOSED

MORE THAN 3 VOLTS WITH THROTTLE VALVE OPEN

VTA1 – E2:

CONTINUITY WITH THROTTLE VALVE FULLY CLOSED
APPROX. 4K

 WITH THROTTLE VALVE FULLY OPEN

VC

– E2:

APPROX. 5 VOLTS

O 1

  O/D DIRECT CLUTCH SPEED SENSOR

1–2 : APPROX. 620

S 4

  SPEED SENSOR NO.2 (FOR ECT)

1–2 : APPROX. 620

S12

  STOP LIGHT SW

2–1 : CLOSED WITH BRAKE PEDAL DEPRESSED

SERVICE HINTS