1991 LEXUS SC300 lumbar support

DESCRIPTION
The Power Seat Control System carries out seat slide, front vertical, rear \
vertical, reclining and lumbar support
position adjustments electrically. Power seat switch and lumbar support switch.
In addition, operation of the memory switch makes it possible to store the positions of the slide, front vertical,
rear vertical and reclining adjustments in memory and return to the posi\
tion.
The component parts of this system and their function are described in t\
he following table.
 Parts Name\
 \
Function
 








Driver's Seat ECU
\
 
\


\


\


\

\

The seat ECU controls power operation, memory operation, and position re\
turn
operation of the power seat. When input is received from the power seat \
switch,
the relay inside the ECU is controlled and the power seat operates. The \
seat
memory and position return are controlled by mutual communication betwee\
n the
electrically operated Tilt and Telescopic ECU and the seat ECU.
 

Power Seat Switch\
 
\

\

Operation of this switch sends slide, front vertical, rear vertical, rec\
lining signals
to ECU.
 




Driving Position
Memory and Return
Switch\
 
\


\

\

Memory and Return Signals are sent to the seat ECU via the Tilt and Telescopic
ECU.
 






Lumbar Support
Switch
\
 
\


\


\

\

This switch is supplied with power from the DOOR fuse. When the switch i\
s
operated, power is supplied to the lumbar support motor controlling the \
direction
in which the motor turns and turning the current ON and OFF. This switch is not
connected to the ECU and the adjustment position cannot be stored in mem\
ory
for return operation.
 

Position Sensor
\
 
\

\
This sensor sends signals on the position of each motor (slide, front v\
ertical, rear
vertical and reclining) to the ECU for use in memory and return.
 

*Motor
\
 
\

\

These motors operate on current from the driver's seat ECU moving the various
parts of the seat directly. Each motor has a built±in circuit breaker.
*: Slide, Front Vertical, Rear Vertical, Lumbar Support and Reclining.
Motors contained in each seat are described in the following table.
 Motor Slide Front
Vertical
 Rear
Vertical
 Reclining Lumbar
Support 

Seat 

Motor 


Vertical
Motor
 


Vertical
Motor
 


g
Motor 


Support
Motor
 Driver's Seat O* O* O* O* O
*: Operated by the memory and return functions. BE±266
±
BODY ELECTRICAL SYSTEM Power Seat Control System (Driver's Seat)
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CUSTOMER PROBLEM ANALYSIS CHECK SHEET
POWER SEAT Check Sheet
Inspector 's
Name :
 


 


 

Registration No.
 


 

Customer 's Name
 


 

Registration Year
 

//
 


 


 

Frame No.
 


 

Date Vehicle
Brought In 

//
 

Odometer Reading
 

Km
Miles
 

Condition of
Problem
 

Date Problem
Occurrence\
 

\
//
 



Problem
Occurrence 



How Often does
Problem Occur?
\
 





Continuous
Intermittent ( times a day)
 




 






Manual Function
does not operate
\
 



\



Slide
Front Vertical

Rear Vertical
Reclining
Lumbar Support
 








Symptoms
 










Return Function
does not operate\
 







\



Slide
Front Vertical

Rear Vertical
Reclining

Does not operate in any conditions

Only with key inserted

Only with key not inserted

Only with memory & return switch 1 or 2
 \
 \

Memory function does not operate. 


\
 
\

\


Position return function does not stop when brake pedal is depressed.
For ªReturn function does not operateº malfunctions, check the ret\
urn operation of the items below.
 


Ch k It
 

Tilt & Telescopic
\
 

\


OK
NG
 


Check Item 

Outer Mirror
\
 

\


OK
NG
BE±270±
BODY ELECTRICAL SYSTEM Power Seat Control System (Driver's Seat)
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1Position sensor check (Cont'd)
OK Code
NG Code
OK
Hint
Hint
(4) Operate the power seat switch and check thechange in the voltage when the seat is moving.
The lumbar support does not have a position sensor, so
the sensor check cannot be done.
(5) The changes in the output voltage when the input signal is normal and when it is abnormal are shown
in the illustrations. Compare the results with those
from (4) and diagnose the condition of each circuit.

The OK and NG codes continue to be output while
the manual switch is ON.

When the seat reaches the limit of movement, e.g.
when the slide position reaches the most forward
or back position, the voltage changes from the OK
code to the NG code.
After operating any of the system functions with no
problem and confirming the OK code and NG code
by comparing the amount of wavering of the
voltmeter needle, inspect the function with a
problem.

The amount of wavering of the voltmeter needle
depends on the meter.
OutputOK Code
NG Code
OK
NG
BE±296±
BODY ELECTRICAL SYSTEM Power Seat Control System (Driver's Seat)
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32
ELECTRICAL WIRING ROUTING
Position of Parts in Seat
B 4 Buckle SW LH P 15 Power Seat Motor (for Driver's Seat Rear Vertical Control)
B 5 Buckle SW RH P 16 Power Seat Motor (for Driver's Seat Reclining Motor Control)P 17 Power Seat Motor (for Driver's Seat Slide Control)
F 19 Front Vertical Position Sensor P 18 Power Seat Motor (for Passenger's Seat Reclining Control) P 19 Power Seat Motor (for Passenger's Seat Slide Control)
P 8 Power Seat Control SW (for Driver's Seat)
P 9 Power Seat Control SW (for Passenger's Seat) R 19 Rear Vertical Position Sensor
P 10 Power Seat ECU (for Driver's Seat) R 20 Reclining Limit SW
P 11 Power Seat ECU (for Driver's Seat)
P 12 Power Seat ECU (for Passenger's Seat) S 15 Seat Heater (for Driver's Seat Back)
P 13 Power Seat Motor (for Driver's Seat Front Vertical Control) S 16 Seat Heater (for Driver's Seat Cushion)
P 14 Power Seat Motor (for Driver's Seat Lumbar S 17 Seat Heater (for Passenger's Seat Back) Support Control) S 18 Seat Heater (for Passenger's Seat Cushion) S 19 Slide Limit SW
S 20 Slide Position Sensor (for Driver's Seat)
S 21 Slide Position Sensor (for Passenger's Seat)
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567 8
11 LEXUS SC300(
Cont ' d )
2 1
M
2
1M
2
1M
M BK
Ba 1 Ba1 Ba1
8Ba1 3Ba1
Ba 14Bb1BL
17 BX1 18 BX1
18 BX1
5Bb1 6Bb1 7Bb1
Ba1
7
1 21
42
3
23222 13651 1313
CDC
D
C C C C C C C DDDDDDDD
D DCD DDDC
M
21 M
12
D
C
C
2Ba1
346251
10 12 11
3
4
8
69
5
2
1
131
2
7
14
2
C
6 7 7152 9 4 111312145 10
193114122
16 6 14 3 10 5 15 8 17 1 8 18
B±R
R
L±W L±W R
GR
B±R
RL±W
R
L±W
VVV W±B W±B
BR±B
L±W
L±W
G±W
BR±B BR±B BR±B BR±B
BR± B
BR± BB
W Y±B BR BR BR
L±W
W± B BR BR
W±B W±B W±B
L
L±B V
LG
BR
BR
L±Y L±R
L±W
L±W
L±Y
L±R
V± R
W± B R
B
V± W
LG±R Y BR
BR
BR
B
R
L±W L±W
RB±R
B±R
L±W
V±B Y± R
Y±L
Y±G L±R
L±Y
L±B LL±W L±W
Y± L
Y± G L±RL±Y
L±B L
GR
G±W
LG
V
V
V Y±G
V± W
Y±R
Y±B
WB
W± B
W± B
BR±B
W± B
W
B
W± B
BR±B BR±B
BR±B
BR±B BR±B
G± W
B± R
SSRS PVCC SSSR RCL+ RCL± SSFV SSRV SI SO GND GND2 SGND
STOP I G SYSB P SLD+ SLD± FRV+ FRV± RRV+ RRV± +B2 +B
SL DFSLDR
FUPFDWN
RUPRDWN
RCLFRCLR
+B SYSB PRDC SLSW RRSW RFSW
SLDR SLDF GND SLD+ SLD± PVCC SSRS SGND 5 6 16 7 17 3 11 15 81 9 2 13 10
21
M
R
4912 13
G±R
G
P8
POWER SEAT CONTROL SW
(for Driver' s Seat )
From Stop Light SW
< 4±6> < 5±6>
POWER SEAT ECU (
Dr i ver ' s S sa t )
S20
SLI DE
POSITION
SENSOR LH P16
POWER
SEAT MOTOR
(
f or Driver' s
Seat Rclining
Contr ol ) F1 9
FRONT
VERTICAL
POSITI ON
SENSOR
R1 9
RE AR
VERT I CAL
POSI TI ON
SENSOR
P18
P OWE R S EA T MOT OR
(for Pass enger' s Seat
Reclining Control )
P9
POWER SEAT
CONTROL SW
(
for Pas senger ' S
Seat )
S21
SLIDE
POSI TION
SENSOR RH
P1 9
POWER SEAT MOTOR
(
for Passenger' s
Se at Sli d e
Co nt r o l )
T18
TENSION
REDUCER
SOLENOID LH
S1 9
SLIDE LIMIT SW
R2 0
RECLINING LIMIT SW
P12
POWER SEAT ECU (
Pas senger ' s Seat )
(
SHI ELDED )
Power Seat (
Driver' s ) Power Seat
(
Passenger' s )
and
Electric Tension Reducer
P15
POWER SEAT MOTOR
( for Driver' s Seat
Slide Control )
P13
POWER SEAT MOTOR
( for Driver' s Seat
Front Vertic al
Control )
P14
POWER SEAT MOTOR
( for Driver' s Seat
Rear Vertical
Control )
SL I DE F RONT SL I DE REARF. VER. UP
F . VE R. DOWN R. VER. UP
R. VER. DOWN RE C. F RONTRE C. RE AR
LUMBAR
SUPPORT FRONT
REAR
P14
POWER SEAT MOTOR
(
f or Driver' s Seat
Lumbar Suppor t
Cont rol )
D
LG±R
1 2BB±RT19
TE NS I ON REDUCER
SOLE NOI D RH
To Buc kl e
SW LH
<4±4><5±4>
D3
DIODE
(
f or Tens ion
Reducer )
B±L
L±W
RE AR
FRONT
VCC O/ P
GND
FRONT
RE AR
FRONT
RE AR
SLIDE RECLINING
B± R
P10 , P11 C
C 1 2
B±Y BRPBCL
12B5
BUCKLE SW RH2
134567
8 9 10 11 12 13 14 15 16
12 34 56 78
9 10 1112 13 14 1516 1718 D C
P10
P11
POWER SEAT ECU
(
Driver' s )
Under the center
pillar LH Under the center
pillar RH
2
1
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OVERALL ELECTRICAL WIRING DIAGRAM
1234
23 LEXUS SC300(
Cont ' d )
5Ba2
BK
M
21
12
7W± B W± B L
L±B
P1 7
POWER SEAT MOTOR
( for Driver' s Seat
Si de Con t ro l )FRONT
REAR
SL I DE
Under the center
pillar LH
4Ba2
L±W
L±W
FRONT VERTICALUPP1 3
POWER SEAT MOTOR
(
for Driver' s Seat
Front Ver tical Cont rol )L±Y
DOWN
L±R
M
21
56 REAR VERTI CAL
UPP15
POWER SEAT MOTOR
(
for Rear Vert ical
Control )Y±G
DOWN
Y±L
M
21
98 LUMBAR SUPPORT
RE L EA SEP1 4
POWER SEAT MOTOR
(
for Driver' s Seat
Lumbar Support Control )G±R
PUSH
G
M
21
10 12
3
4 RE CL I NI NG
FRONTP16
POWER SEAT MOTOR
(
for Reclining
Motor Cont rol )Y±R
REAR
Y±B
M
21 11
P8
POWER SEAT CONTROL SW
(
for Driver' s Seat )
1C
8
1B
2
4
6
L±W
W± L
W
30A
DOOR
BATTERY100A AM1
120A ALT
F9
FUSE BLOCK
6
5
Power Seat
(
w/o Driving Positiotn Memory )
Power Source
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50
POWER SOURCE (Current Flow Chart)*1: USA
*2: CANADA
P18
P11
N2 N4 O2 P2 O8 P4 P6 R5 R4 P20
P14
226
154
192
154
190 68 154 90
202
202
P8
P7
184 94
O5 P5 P3
Parking Brake SW
Power Window Motor RH Power Window Motor LHOil Pressure SW
Power Seat Control SW
(for Driver's Seat)
Power Seat Control SW
(for Passenger's Seat)Power Seat ECU (Passenger's)Oxygen Sensor Sub
(for California)Power Seat Motor (for Driver's
Lumbar Support Control)O/D Main SW
Radio and Player Personal LightRadio and Player (w/ CD Player)Noise Filter
(for A/C System)Power Seat Motor (for Passenger's
Reclining Control)PPS ECU
Power Window Control SW RH
Power Window Master SW and
Door Lock Control SW LH
*Page Nos. of
Related Systems Parts
Code or
Location
CB or Fuse
50A DEFOG
30A DOOR
30A POWER
15A STOP
15A ECU±B
10A MIR±HTR
10A HEATER
20A TURN
20A WIPER
10A GAUGE
15A ECU±IG
7.5A ENGINE
7.5A IGN
15A CIG
7.5A RADIO No.2
15A TAIL
7.5A PANEL
7.5A ST
15A TEL
10A DOME
20A RADIO No.1
25A HAZ±HORN
30A EFI
7.5A ALT SENCING
15A HEAD LH*1
15A HEAD RH*1
15A HEAD LH±LWR*2
15A HEAD RH±LWR*2
15A HEAD LH±UPR
15A HEAD RH±UPR
60A HEATER
7.5A TRAC
15A SEAT±HTR
LocationP9 P12 P10 R2
Power Seat ECU (Driver's)Noise Filter
(for Defogger System)
216 126 216 208
122


* These are the page numbers of the first page on which the related system\
is shown.
The part indicated is located somewhere in the system, not necessarily o\
n the page indicated here.
[LOCATION](1): J/B No. 1 (See page 20)(2): R/B No. 2 (See page 19)(3): R/B No. 4 (See page 23)
20
19 22
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162
POWER SEAT (w/o DRIVING POSITION MEMORY)
FROM POWER SOURCE SYSTEM(
SEE PAGE 56 )
30A
DOOR
1C
8
Ba2
4
BK
Ba2
5
POWER SEAT CONTROL SW
(
FOR DRIVER' S SEAT )
REARFRONT
HOLD RE LEA SE
12
12
7
UP
DOWN FRONT
REAR UP
DOWN
5643981011 P8
M
12
M
21
M
21
M
21
M
21
G±R
GL
L±B
L±Y
L±R
Y±R
Y±B
Y±G
Y±L L±W
L±W
W±B
W±B
POWER SEAT MOTOR
(
FOR DRIVE R' S SE AT
SLIDE CONTROL )POWER SEAT MOTOR
(
FOR DRIVER' S SEAT
FRONT VERTI CA L
CONTROL ) POWER SEAT MOTOR
(
FOR DRIVE R' S SE AT
RECLINING MOTOR
CONTROL ) POWER SEAT MOTOR
(
FOR DRIVER' S SEAT
REAR VERTICAL
CONTROL ) POWER SEAT MOTOR
(
FOR DRIVE R' S SE AT
LUMBAR SUPPORT
CONTROL )
P17 P13 P16 P15 P14 SLIDE FRONT VERTICAL RECLINING REAR VERTICAL LUMBAR SUPPORT
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