1991 LEXUS SC400 Service Repair Manual

ignition USB cabin filter belt fuel cap alarm

Page 4017 of 4087

LEXUS SC400 1991 Service Repair Manual
159
RETURN OPERATION
WHEN THE SEAT BACK IS RAISED UP FROM THE WALK±IN POSITION AND RETURNED TO THE UPRIGHT LOCK POSITION,
RECLINING LIMIT SWITCH NO. 1 OPERATES AND A SIGNAL IS INPUT TO TERMINAL RRSW

159
RETURN OPERATION
WHEN THE SEAT BACK IS RAISED UP FROM THE WALK±IN POSITION AND RETURNED TO THE UPRIGHT LOCK POSITION,
RECLINING LIMIT SWITCH NO. 1 OPERATES AND A SIGNAL IS INPUT TO TERMINAL RRSW OF THE POWER SEAT ECU " TERMINAL
SLD± " TERMINAL 2 OF POWER SEAT MOTOR (FOR PASSENGER'S SEAT SLIDE CONTROL) " MOTOR " TERMINAL 1 " TERMINAL
SLD+ OF ECU " TERMINAL GND " GROUND . THIS CAUSES THE SEAT TO SLIDE BACK TO A POSITION 120 MM FROM THE MOST
REAR POSITION, COMPLETING RETURN OPERATION. HOWEVER, IF THE SEAT IS POSITIONED WITHIN 120 MM OF THE MOST REAR
POSITION, RETURN OPERATION DOES NOT OCCUR, THUS MAINTAINING SUFFICIENT SPACE FOR THE REAR SEAT PASSENGER.
D10 DOOR LOCK MOTOR, DOOR UNLOCK DETECTION SW AND DOOR OPEN DETECTION SW LH
3±6 : CLOSED WITH FRONT LH DOOR OPEN
N 1 A/T INDICATOR SW [NEUTRAL START SW]
9±1 : CLOSED WITH SHIFT LEVER AT ªPº POSITION
P10(A), P11(B) POWER SEAT ECU (FOR DRIVER'S SEAT)
(A) 6±GROUND : APPROX. 12 VOLTS WITH STOP LIGHT SW ON
(B) 7±GROUND : ALWAYS APPROX. 12 VOLTS
(A) 7±GROUND : APPROX. 12 VOLTS WITH IGNITION SW ON
(A) 15±GROUND : APPROX. 12 VOLTS WITH IGNITION SW ON AND SHIFT LEVER AT ªPº RANGE
(A) 2±GROUND : APPROX. 12 VOLTS WITH DRIVER'S SEAT AT FRONT SLIDE OPERATION
(A) 9±GROUND : APPROX. 12 VOLTS WITH DRIVER'S SEAT AT REAR SLIDE OPERATION
(A) 4±GROUND : APPROX. 12 VOLTS WITH DRIVER'S SEAT AT FRONT VERTICAL UP OPERATION
(A) 11±GROUND : APPROX. 12 VOLTS WITH DRIVER'S SEAT AT FRONT VERTICAL DOWN OPERATION
(A) 13±GROUND : APPROX. 12 VOLTS WITH DRIVER'S SEAT AT REAR VERTICAL UP OPERATION
(A) 12±GROUND : APPROX. 12 VOLTS WITH DRIVER'S SEAT AT REAR VERTICAL DOWN OPERATION
(B) 18±GROUND : ALWAYS CONTINUITY
(A) 5, (A) 14±GROUND : ALWAYS APPROX. 12 VOLTS
(A) 1, (A) 8±GROUND : ALWAYS CONTINUITY
P 8 POWER SEAT CONTROL SW (FOR DRIVER'S SEAT)
4±14 : CLOSED WITH DRIVER'S SEAT AT FRONT RECLINING OPERATION
3±14 : CLOSED WITH DRIVER'S SEAT AT REAR RECLINING OPERATION
1±14 : CLOSED WITH DRIVER'S SEAT AT FRONT SLIDE OPERATION
2±14 : CLOSED WITH DRIVER'S SEAT AT REAR SLIDE OPERATION
5±14 : CLOSED WITH DRIVER'S SEAT AT FRONT VERTICAL UP OPERATION
6±14 : CLOSED WITH DRIVER'S SEAT AT FRONT VERTICAL DOWN OPERATION
9±14 : CLOSED WITH DRIVER'S SEAT AT REAR VERTICAL UP OPERATION
8±14 : CLOSED WITH DRIVER'S SEAT AT REAR VERTICAL DOWN OPERATION
P12 POWER SEAT ECU (FOR PASSENGER'S SEAT)
1±GROUND : ALWAYS APPROX. 12 VOLTS
8±GROUND : ALWAYS APPROX. 12 VOLTS
7±GROUND : APPROX. 12 VOLTS WITH PASSENGER'S SEAT AT FRONT SLIDE OPERATION
17±GROUND : APPROX. 12 VOLTS WITH PASSENGER'S SEAT AT REAR SLIDE OPERATION
S12 STOP LIGHT SW
2±1 : CLOSED WITH STOP LIGHT SW ON
SERVICE HINTS
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Page 4018 of 4087

LEXUS SC400 1991 Service Repair Manual
160
POWER SEAT (w/ DRIVING POSITION MEMORY)
: PARTS LOCATION
CODESEE PAGECODESEE PAGECODESEE PAGE
B532P11B32R1932
D1030P1232R2032
D1230P1332S1232
F1932P1432S1932
N 127P1532S2029
P 329P1632S2132
P 832

Page 4019 of 4087

LEXUS SC400 1991 Service Repair Manual
161
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Page 4020 of 4087

LEXUS SC400 1991 Service Repair Manual
164POWER TILT AND POWER TELESCOPIC
1H
15 1K 13 2
1H
10 1B
5
AAB
B±R
L±W
RR
30A
POWER 15A
ECU±IG10A
DOME
4118 +B I G ECU ± B TILT AND POWER TELESCOPIC ECU
FROM POWER SOURCE SYSTEM
(
SEE PAGE 56 )

Page 4021 of 4087

LEXUS SC400 1991 Service Repair Manual
165
1H
12
PRND 2 L
146578 9
B B BB BAA B AA A
2 1M
2 1 M
2
1
VC MSW E ASW TIS TIM+ TIM± VC TES E TEM+ TEM± Y
BR
R±W
GR
R±B
L
G±W G
W
R±W
BR
R±W BR R±W
V±Y
BR
V±W
P±L
R±B R±L
Y±R
L±B
L�

Page 4022 of 4087

LEXUS SC400 1991 Service Repair Manual
166POWER TILT AND POWER TELESCOPIC
THIS SYSTEM OPERATES WITH BOTH THE TILT FUNCTION AND TELESCOPIC FUNCTION DRIVEN AUTOMATICALLY BY THE MOTOR
AND CONTROLLED BY THE ECU. THE STEERING CAN BE ADJUSTED S

166POWER TILT AND POWER TELESCOPIC
THIS SYSTEM OPERATES WITH BOTH THE TILT FUNCTION AND TELESCOPIC FUNCTION DRIVEN AUTOMATICALLY BY THE MOTOR
AND CONTROLLED BY THE ECU. THE STEERING CAN BE ADJUSTED STEPLESSLY FORWARD AND BACK, AND UP AND DOWN, TO
PROVIDE THE MOST SUITABLE STEERING POSITION FOR EASY DRIVING, WITH AUTOMATIC MOVEMENT OF THE STEERING TO A
POSITION WHICH FACILITATES GETTING IN AND OUT OF THE VEHICLE.
THE DRIVER CAN HAVE THE MOST APPROPRIATE DRIVING POSITION MEMORIZED BY OPERATING THE POWER SEAT AND REMOTE
CONTROL MIRROR TOGETHER WITH THE TILT AND POWER TELESCOPIC STEERING.
CURRENT IS ALWAYS APPLIED THROUGH THE
POWER FUSE TO TERMINAL +B OF THE TILT AND POWER TELESCOPIC ECU AND
THROUGH THE DOME FUSE TO TERMINAL BATT OF TILT AND POWER TELESCOPIC ECU.
WITH THE IGNITION SW TURNED ON, THE CURRENT FLOWS FROM ECU±IG FUSE TO TERMINAL IG AND FROM GAUGE FUSE TO
TERMINAL 9 OF A/T INDICATOR SW.
1. MANUAL TILT OPERATION
WHEN THE IGNITION KEY IS INSERTED INTO THE IGNITION KEY CYLINDER (UNLOCK WARNING SW ON), A SIGNAL IS INPUT TO
TERMINAL UWSW OF TILT AND POWER TELESCOPIC ECU. IF THE MANUAL SW IS PUSHED TO THE ªTILT UPº SIDE, CURRENT
FLOWS FROM TERMINAL VC OF TILT AND POWER TELESCOPIC ECU TO TERMINAL MSW OF TILT AND POWER TELESCOPIC ECU
PASSING THROUGH THE MANUAL SW. (THE ECU DETECTS THE MANUAL SW POSITION BY THE VOLUME OF CURRENT.)
AS A RESULT, TILT AND POWER TELESCOPIC ECU OPERATES AND THE CURRENT TO TERMINAL +B OF ECU FLOWS FROM
TERMINAL TIM+ " TERMINAL 1 OF COMB. SW " TERMINAL 2 OF TILT CONTROL MOTOR " TERMINAL 1 " TERMINAL 10 OF COMB.
SW "TERMINAL TIM± OF TILT AND POWER TELESCOPIC ECU " TERMINAL GND2 "GROUND , AND THE TILT UP FUNCTION
OPERATES AS LONG AS THE MANUAL SW IS PUSHED TO THE ªTILT UPº SIDE.
FOR ªTILT DOWNº OPERATION, WHEN THE MANUAL SW IS PUSHED TO THE DOWN SIDE, THE CURRENT FLOWING FROM ECU TO
MOTOR FLOWS TO TERMINAL TIM± OF TILT AND POWER TELESCOPIC ECU "TERMINAL 10 OF COMB. SW "TERMINAL 1 OF TILT
CONTROL MOTOR "TERMINAL 2 "TERMINAL 1 OF COMB. SW "TERMINAL TIM+ OF TILT AND POWER TELESCOPIC ECU, SO THE
MOTOR ROTATES IN THE REVERSE DIRECTION TO TILT UP OPERATION, AND TILT DOWN OPERATION OCCURS ONLY WHILE THE
MANUAL SW IS BEING PUSHED.
2. MANUAL TELESCOPIC OPERATION
WHEN THE IGNITION KEY IS INSERTED INTO THE IGNITION KEY CYLINDER (UNLOCK WARNING SW ON), A SIGNAL IS INPUT TO
TERMINAL UWSW OF TILT AND TELESCOPIC ECU. WHEN THE MANUAL SW IS PUSHED TOWARD ªTELESCOPIC SHORTº SIDE,
CURRENT FLOWS FROM TERMINAL VC OF TILT AND POWER TELESCOPIC ECU TO TERMINAL MSW OF TILT AND POWER
TELESCOPIC ECU THROUGH THE MANUAL SW.
AS A RESULT, THE TILT AND POWER TELESCOPIC ECU OPERATES AND THE CURRENT TO TERMINAL +B OF TILT AND POWER
TELESCOPIC ECU FLOWS FROM TERMINAL TEM+ OF TILT AND POWER TELESCOPIC ECU "TERMINAL 1 OF COMB. SW "
TERMINAL 2 OF TELESCOPIC CONTROL MOTOR "TERMINAL 1 "TERMINAL 4 OF COMB. SW "TERMINAL TEM± OF TILT AND
POWER TELESCOPIC ECU " TERMINAL GND2 "GROUND , AND ªTELESCOPIC SHORTº OPERATION OCCURS AS LONG AS THE
MANUAL SW IS PUSHED THE TO ªTELESCOPIC SHORTº SIDE.
FOR ªTELESCOPIC LONGº OPERATION, WHEN THE MANUAL SW IS PUSHED TO THE TELESCOPIC LONG SIDE, CURRENT FLOWING
FROM TILT AND POWER TELESCOPIC ECU TO THE MOTOR FLOWS THROUGH TERMINAL TEM± OF TILT AND POWER TELESCOPIC
ECU " TERMINAL 4 OF COMB. SW "TERMINAL 1 OF TELESCOPIC CONTROL MOTOR "TERMINAL 2 " TERMINAL 1 OF COMB. SW
" TERMINAL TEM+ OF TILT AND POWER TELESCOPIC ECU "TERMINAL GND2 "GROUND .
AS A RESULT, THE MOTOR ROTATES IN REVERSE TO THE TELESCOPIC SHORT MODE AND TELESCOPIC LONG OPERATION
OCCURS AS LONG AS THE MANUAL SW IS PUSHED TO THE ªTELESCOPIC LONGº SIDE.
3. AUTO AWAY OPERATION
WHEN THE IGNITION SW IS TURNED FROM ON TO OFF, THE CURRENT STOPS FLOWING FROM ECU±IG TO TERMINAL IG OF TILT
AND POWER TELESCOPIC ECU AND IS INPUT AS A SIGNAL THAT THE IGNITION SW IS OFF. WHEN THE AUTO SW IS TURNED ON, AN
ªAUTO SW ONº SIGNAL IS INPUT TO TERMINAL ASW OF TILT AND POWER TELESCOPIC ECU.
IF THE IGNITION KEY IS REMOVED FROM THE IGNITION KEY CYLINDER (UNLOCK WARNING SW OFF) AT THIS TIME, A SIGNAL IS
INPUT FROM TERMINAL UWSW OF TILT AND POWER TELESCOPIC ECU. ALSO, THE TILT POSITION SENSOR (COMB. SW) INPUTS
INTO TERMINAL TIS OF THE TILT AND TELESCOPIC ECU A SIGNAL OF THE STEERING TILT POSITION JUST BEFORE THE IGNITION
SW (FOR UNLOCK WARNING) IS TURNED FROM ON TO OFF.
AS A RESULT, THE TILT AND POWER TELESCOPIC ECU OPERATES AND THE CURRENT TO TERMINAL +B OF TILT AND POWER
TELESCOPIC FLOWS FROM TERMINAL TIM+ OF TILT AND POWER TELESCOPIC ECU "TERMINAL 1 OF COMB. SW "TERMINAL 2
OF TILT CONTROL MOTOR "TERMINAL 1 "TERMINAL 10 OF COMB. SW "TERMINAL TIM± OF TILT AND POWER TELESCOPIC ECU
" TERMINAL GND2 "GROUND , CAUSING THE MOTOR TO ROTATE SO THAT ªTILT UPº OPERATION OCCURS AUTOMATICALLY.
AT THE SAME TIME, THE CURRENT FROM TERMINAL +B OF TILT AND POWER TELESCOPIC ECU TO TERMINAL TEM+ FLOWS FROM
TERMINAL 1 OF COMB. SW "TERMINAL 2 OF TELESCOPIC CONTROL MOTOR "TERMINAL 1 "TERMINAL 4 OF COMB. SW "
TERMINAL TEM± OF TILT AND POWER TELESCOPIC ECU "TERMINAL GND2 "GROUND , CAUSING THE MOTOR TO ROTATE SO
THAT TELESCOPIC SHORT OPERATION OCCURS ON AUTO AND WITH TILT UP OPERATION OCCURRING SIMULTANEOUSLY ON
AUTO, AUTO AWAY OPERATION OCCURS.
SYSTEM OUTLINE
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Page 4023 of 4087

LEXUS SC400 1991 Service Repair Manual
167
4. AUTO RETURN OPERATION
WHEN THE STEERING IS IN ªAUTO AWAYº CONDITION AND THE IGNITION KEY IS INSERTED INTO THE IGNITION KEY CYLINDER
(UNLOCK WARNING SW ON), A SIGNAL IS INPUT TO TERMINAL UWSW

167
4. AUTO RETURN OPERATION
WHEN THE STEERING IS IN ªAUTO AWAYº CONDITION AND THE IGNITION KEY IS INSERTED INTO THE IGNITION KEY CYLINDER
(UNLOCK WARNING SW ON), A SIGNAL IS INPUT TO TERMINAL UWSW OF TILT AND POWER TELESCOPIC ECU.
AS A RESULT, THE TILT AND POWER TELESCOPIC ECU OPERATES AND THE CURRENT TO TERMINAL +B OF TILT AND POWER
TELESCOPIC ECU FLOWS FROM TERMINAL TEM± OF TILT AND POWER TELESCOPIC ECU "TERMINAL 4 OF COMB. SW "
TERMINAL 1 OF TELESCOPIC CONTROL MOTOR "TERMINAL 2 " TERMINAL 1 OF COMB. SW " TERMINAL TEM+ OF TILT AND
POWER TELESCOPIC ECU " TERMINAL GND2 "GROUND , AND AT THE SAME TIME, CURRENT FLOWS FROM TERMINAL TIM± OF
TILT AND POWER TELESCOPIC ECU "TERMINAL 10 OF COMB. SW "TERMINAL 1 OF TILT CONTROL MOTOR "TERMINAL 2 "
TERMINAL 1 OF COMB. SW "TERMINAL TIM+ OF TILT AND POWER TELESCOPIC ECU "TERMINAL GND2 "GROUND , CAUSING
BOTH THE TILT CONTROL MOTOR AND TELESCOPIC CONTROL MOTOR TO ROTATE. THE MOTORS CONTINUE TO ROTATE UNTIL
THE SIGNALS INPUT FROM THE TILT POSITION SENSOR TO TERMINAL TIS OF TILT AND POWER TELESCOPIC ECU AND FROM THE
TELESCOPIC POSITION SENSOR TERMINAL TES OF TILT AND POWER TELESCOPIC ECU (SIGNALS INFORMING THE ECU OF THE
CURRENT POSITION OF THE STEERING) MATCH THE POSITION MEMORIZED BY THE ECU PRIOR TO AUTO AWAY OPERATION.
IN THIS WAY, THE STEERING POSITION IS AUTOMATICALLY RETURNED TO THE ORIGINAL POSITION.
WHEN THE IGNITION SW IS TURNED FROM OFF TO ON OR THE SHIFT LEVER IS SHIFTED TO A POSITION OTHER THAN P OR N,
AUTO OPERATION IS STOPPED.
C15 TILT AND POWER TELESCOPIC UNIT [COMB. SW]
4±6 : APPROX. 160 WITH TELESCOPIC LONG OPERATION
: APPROX. 360 WITH TILT UP OPERATION
: APPROX. 790 WITH TELESCOPIC SHORT OPERATION
: APPROX. 2.0K WITH TILT DOWN OPERATION
8±7 : CONTINUITY WITH AUTO SW OFF
8±4 : APPROX. 5K
T 7 (D) TELESCOPIC POSITION SENSOR
6±3 : APPROX. 5K
D10 DOOR LOCK MOTOR, DOOR UNLOCK DETECTION SW AND DOOR OPEN DETECTION SW LH
3±6GROUND :CLOSED WITH FRONT DOOR LH OPEN
D12 DRIVING POSITION MEMORY AND RETURN SW
2±3 : CLOSED WITH DRIVING POSITION MEMORY SW (NO. 1) ON
1±3 : CLOSED WITH DRIVING POSITION MEMORY SW (NO. 2) ON
4±3 : CLOSED WITH DRIVING POSITION MEMORY SW (SET) ON
I15 UNLOCK WARNING SW [IGNITION SW]
9±10: CLOSED WITH IGNITION KEY IN CYLINDER
N 1 A/T INDICATOR SW [NEUTRAL START SW]
9±1 : CLOSED WITH SHIFT LEVER AT P POSITION
T10, T11 TILT AND POWER TELESCOPIC ECU
(A) 4±GROUND : ALWAYS APPROX. 12 VOLTS
(A) 1±GROUND : APPROX. 12 VOLTS WITH IGNITION SW AT ON POSITION
(B) 18±GROUND : ALWAYS APPROX. 12 VOLTS
(A) 6±GROUND : APPROX. 12 VOLTS WITH IGNITION SW ON AND SHIFT LEVER AT ªPº RANGE
(B) 10±GROUND : CONTINUITY WITH IGNITION KEY IN CYLINDER
(A) 7±GROUND : ALWAYS CONTINUITY
(B) 8±GROUND : ALWAYS CONTINUITY
(B) 2±GROUND : CONTINUITY WITH FRONT DOOR LH OPEN
(B) 3±GROUND : CONTINUITY WITH DRIVING POSITION MEMORY SW (NO. 1) ON
(B) 12±GROUND : CONTINUITY WITH DRIVING POSITION MEMORY SW (NO. 2) ON
(B) 11±GROUND : CONTINUITY WITH DRIVING POSITION MEMORY SW (SET) ON
(A) 10±GROUND : APPROX. 12 VOLTS WITH TILT UP OPERATION
(A) 3±GROUND : APPROX. 12 VOLTS WITH TILT DOWN OPERATION
(A) 2±GROUND : APPROX. 12 VOLTS WITH TELESCOPIC SHORT OPERATION
(A) 11±GROUND : APPROX. 12 VOLTS WITH TELESCOPIC LONG OPERATION
: PARTS LOCATION
CODESEE PAGECODESEE PAGECODESEE PAGE
C1728N 127T 732
D1030P 329T10B29
D1230P1127T11A29
I1529R 732
SERVICE HINTS
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Page 4024 of 4087

LEXUS SC400 1991 Service Repair Manual
168POWER TILT AND POWER TELESCOPIC
: RELAY BLOCKS
CODESEE PAGERELAY BLOCKS (RELAY BLOCK LOCATION)
219ENGINE COMPARTMENT LEFT
: JUNCTION BLOCK AND WIRE HARNESS CONNECTOR
CODESEE PAGEJUNCTION BLOCK AND

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