seat memory LEXUS SC400 1991 Service User Guide

Fuel Pump ECUAuto Antenna Motor and Relay
Power Seat ECU
(For Passenger's Seat)
Power Seat ECU
(For Driver's Seat) CD Automatic Changer
Wireless Door Lock ECU
Moon Roof Control Relay
Locations of ECUs (Cont'd)
Many ECUs are mounted in this vehicle.
Take the following precautions during body repair to prevent damage to th\
e ECUs.


Before starting electric welding operations, disconnect the negative (-\
) terminal cable from the battery.
When the negative (-) terminal cable is disconnected from the battery, memory of the clock and audio
systems will be cancelled. So before starting work, make a record of the\
contents memorized by each
memory system. Then when work is finished, reset the clock and audio sys\
tems as before.
When the vehicle has tilt and telescopic steering, power seat and outsid\
e rear view mirror, which are all
equipped with memory function, it is not possible to make a record of th\
e memory contents.
So when the operation is finished, it will be necessary to explain this \
fact to the customer, and request
the customer to adjust the features and reset the memory.

Do not expose the ECUs to ambient temperatures above 80 °C (176 °F).
NOTICE: If it is possible the ambient temperature may reach 80°C (176°F) or, more, remove the ECUs
from the vehicle before starting work.

Be careful not to drop the ECUs and not to apply physical shocks to them\
.
5. COMPONENTS ADJACENT TO THE BODY PANELS
Various types of component parts are mounted directly on or adjacently to\
the body panels.
Strictly observe the following precautions to prevent damaging these com\
ponents and the body panels
during handling.

Before repairing the body panels, remove their adjacent components or ap\
ply protective covers over
the components.

Before prying components off using a screwdriver or a scraper, etc., attach protective tape to the tool
tip or blade to prevent damaging the components and the body paint.

Before removing components from the outer surface of the body, attach protective tape to the body to
ensure no damage to painted areas.
HINT: Apply touch-up paint to any damaged paint surfaces.

Before drilling or cutting sections, make sure that there are no wires, \
hoses, etc., on the reverse side.
INTRODUCTIONIN-9
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SR±52).
IN±33).
WIRING DIAGRAM
Set Switch Circuit
CIRCUIT DESCRIPTION
When switch 1 or 2 is pushed while SET switch is being pushed ON in memory o\
peration, a signal is sent
to the ECU to memorize the present positions of the tilt, telescopic, seat\
and mirror.
DIAGNOSTIC CHARTDIAGNOSTIC CHART
SR±88±
STEERING STEERING COLUMN
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SR±52).
IN±33).
WIRING DIAGRAM
Memory & Return Switches Circuit
CIRCUIT DESCRIPTION
A memory command signal when switch 1 or 2 pushed while SET
switch is being pushed ON or a return command signal when
switch 1 or 2 is pushed ON is sent to the ECU for memory and re-
turn operations of the tilt, telescopic, seat and mirror.
DIAGNOSTIC CHARTDIAGNOSTIC CHART
SR±90±
STEERING STEERING COLUMN
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DESCRIPTION
By operating the driving position memory and return switch the driver's seat, steering wheel and outer mir-
ror are moved to their respective memorized positions.
 

Parts Name\
 
\

\
Function 




Tilt & Telescopic ECU
\
 
\


\

\

Control the manual operation, return operation and memory and return ope\
ration for tilt
and telescopic of steering wheel.
 Auto Set Switch\
 \
This switch is a main switch for the away operation of tilt and telescop\
ic.
 




Manual Switch\
 
\


\

\

This switch is an operation switch to operate tilt and telescopic manual\
ly. When one of tilt
up, tilt down, telescopic Extension and telescopic Contraction is operat\
ed, steering wheel
will be able to set on the optional position within the extent of operat\
ing.
 


Driving Position
Memory and
Return Switch\
 
\

\

Operating this switch makes return operation that driver seat steering w\
heel and outer mirror
are set on the memorized position working together power seat and outer \
mirror.
 

Position Sensor
\
 
\

\
Tilt position sensor detect an amount of tilt and input it to ECU.
Telescopic position sensor detect an amount of slide and input it to ECU.\
 

Motor
\
 
\

\
There is a tilt motor and telescopic motor respectively. These are operated by a signal from
the ECU.
SR±40±
STEERING STEERING COLUMN
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STANDARD VALUE OF ECU TERMINAL
 

Terminals
 

Symbols
 

Wiring
Color 

Condition
 

Standard
Value
 

T9±1 

Si 

B 


Tilt & telescopic ECU & power seat ECU
communication 

0 V
e12 V
 T9±2 e DSW e R±Be Driver's door open Below 1 V
 
T9 2 e
Body Ground 
DSW e
Body Ground 
RBe
Body GroundDriver's door closed1014 V
 T9±3 eT9±8 M1 eECU±E Pe BR±B Driving position memory & return switch ON Below 1 V
 T9±3eT9±8 M1eECU±E PeBR±B Driving position memory & return switch OFF 10
~ 14 V
 T9±4
eT9±5 ASW eE1 V±W eBR Unlock warning switch ON, auto switch ON 10 ~ 14 V
 T9±4eT9±5 ASWeE1 V±WeBR Unlock warning switch ON, auto switch OFF Below 1 V
 T9±5 E1 BR Always Below 1 V
 

T9±6
eT9±5
 

Te S
eE1
 

Y±R
eBR
 


Unlock warning switch ON, telescopic fully
forward 

Below 2 V
 
T9±6eT9±5
 
TeSeE1
 
Y±ReBR
 Unlock warning switch ON, telescopic fully
backward 4±6 V
 
T9±7
eT9±5
 
TiS eE1
 
P±L eBR
 Unlock warning switch ON, tilt fully raised Below 2 V T9±7eT9±5 TiSeE1 P±LeBR Unlock warning switch ON, tilt fully lowered 4±6 V T9±8 ECU±E BR±B Always Below 1 V 

T9±9
 

So
 

W
 

Tilt & telescopic ECU & power seat ECU
communication 

0 V
e12 V
 T9±10 e UWSW e Ye Ignition key inserted in the key cylinder Below 1 V
 T9 10 e
Body Ground UWSW e
Body Ground Ye
Body Ground Ignition key pulled out from the key cylinder 10
~ 14 V
 
T9±11 eT9±8
 
MRY eECU±E
 
R±Y eBR±B
 Auto set switch ON Below 1 V
 T9±11eT9±8 MRYeECU±E R±YeBR±B Auto set switch OFF 10 ~ 14 V
 
T9±12 eT9±8
 
M2 eECU±E
 
P±B eBR±B
 Driving position memory & return switch ON Below 1 V
 T9±12eT9±8 M2eECU±E P±BeBR±B Driving position memory & return switch OFF 10 ~ 14 V
 


 


 


 


Unlock warning switch ON
Telescopic extend by manual switch 

2.6 V
 


 


 


 


Unlock warning switch ON
Tilt up by manual switch 

3.5 V
 T9±16
eT9±17 MSW eVC V±Y eR±W Unlock warning switch ON
Telescopic contracted by manual switch 4.2 V
 


 


 


 

Unlock warning switch ON
Tilt down by manual switch 

4.6 V
 


 


 


 


Unlock warning switch ON, manual switch
OFF 

4±6 V
±
STEERING STEERING COLUMNSR±49
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GENERAL DESCRIPTION
The LEXUS SC400/300 is equipped with an SRS (Supplemental Restraint System\
) such as the driver
airbag and front passenger airbag. Failure to carry out service operations in \
the correct sequence
could cause the SRS to unexpectedly deployed during servicing, possibly leadin\
g to a serious acci-
dent. Further, if a mistake is made in servicing the supplemental restraint system, i\
t is possible the
SRS may fail to operate when required. Before performing servicing (inc\
luding removal or installa-
tion of parts, inspection or replacement), be sure to read the followin\
g items carefully, then follow
the correct procedure described in the repair manual.
1. Malfunction symptoms of the supplemental restraint system are difficult to confirm, so the diagnostic trouble codes become the most important source of information when troubleshooting. When
troubleshooting the supplemental restraint system, always inspect the diagnostic trouble codes before
disconnecting the battery (See page RS±59).
2. Work must be started after 90 seconds from the time the ignition switch turn\
ed to the LOCK position
and the negative (±) terminal cable is disconnected from the battery. (The supplemental restraint
system is equipped with a back±up power source so that if work is sta\
rted within 90 seconds of
disconnecting the negative (±) terminal cable of the battery, the SRS may be deployed.)
When the negative (±) terminal cable is disconnected from the battery, memory of the clock and audio sys-
tems will be canceled. So before starting work, make a record of the contents memo\
rized by the audio
memory system. When work is finished, reset the audio systems as before and ad\
just the clock. When the
vehicle has power tilt and power telescopic steering, power seat, power outside rear view mirror and power
shoulder belt anchorage, which are all equipped with memory function, it is not \
possible to make a record
of the memory contents. So when the work is finished, it will be necessary\
to explain this fact to the custom-
er, and ask the customer to adjust the features and reset the memory.
To avoid erasing the memory of each memory system, never use a back±up\
power supply from outside
the vehicle.
3. Even in cases of a minor collision where the SRS does not deploy, the steering wheel pad, front passenger
airbag assembly, front airbag sensors and center airbag sensor assembly should be inspe\
cted (See pages
RS±16 , 28 , 41 and 44).
4. Never use SRS parts from another vehicle. When replacing parts, replace \
them with new parts.
5. Before repairs, remove the airbag sensor if shocks are likely to be applied to the sensors during r\
epairs.
6. Never disassemble and repair the steering wheel pad, front passenger airbag a\
ssembly, front airbag sensors or center airbag sensor assembly in order to reuse it.
7. If the steering wheel pad, front passenger airbag assembly, front airbag sensors or center airbag sensor assembly have been dropped, or if there are cracks, dents or dents or ot\
her defects in the case, bracket
or connector, replace them with new ones.
8. Do not expose the steering wheel pad, front passenger airbag assembly, front airbag sensors and center airbag sensor assembly directly to hot air or flames.
9. Use a volt/ohmmeter with high impedance (10 k
/V minimum) of troubleshooting of the system's electrical
circuit.
10. Information labels are attached to the periphery of the SRS components. \
Follow the instructions on the
notices.
11. After work on the supplemental restraint system is completed, perform the SRS\
warning light check (See page RS±59 ).
12. If the vehicle is equipped with a mobile communication system, refer to \
the precaution in the IN section. RS±2
±
SUPPLEMENTAL RESTRAINT SYSTEM GENERAL DESCRIPTION
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194
ELECTRIC TENSION REDUCER
1C
6 1I
8
Bb1
7
BX1
18
Bb1
4
BK BL
2 1
2
1
11
12 15 16
22
9
2 1 B±R
B±R
B
B±R
B
B
B±L
B±L
B±Y
BR
W±B
W±B
W±B
W±B
15A
ECU±IG
TE NSI ON
RE DUCER
SOLENOID LH TENSION
RE DUCER
SOLENOID RH
FROM POWER SOURCE SYSTEM
(
SEE PAGE 56 )
DIODE
( FOR TENSION
REDUCER )
POWER SEAT ECU
(FOR PASSENGER' S SEAT )
BUCKLE
SW LH BUCKLE
SW RHPC SSR± GND
PD
T1 8 T19
D3 P12
B4 B5
Ba2
6 Ba1
11
12
Ba2
5 (
W/ MEMORY POWER SEAT )
( W/O MEMORY POWER SEAT )
Ba1 (W/O MEMORY POWER SEAT )
(
W/ MEMORY POWER SEAT )
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237
GLOVE BOX LIGHT SW
CIGARETTE LIGHTER
LUGGAGE COMPARTMENT
DOOR OPENER SW
COMBINATION METER
(EP )
O/D MAIN SW
RHEOSTAT
DO OR LOCK MOTOR,
DOOR UNLOCK
DETECTION SW AND
DOOR OPEN DETECTION
SW LH
MIRROR HEATER LH DOOR KEY LOCK AND
UNLOCK SW LH
POWER WINDOW
MASTER SW
RE MOTE CO NTROL
MIRROR SW
KEY INTER LOCK
SOLENOID
[IGNITION SW]
UNLOCK WA RNING SW
[IGNITION SW]
TURN SIGNAL SW
[COMB. SW]
WIPER AND WASHER SW
[COMB. SW]
LIGHT CONTROL SW
[COMB. SW]
DIMMER SW
[COMB. SW] INTEGRATION RELAY POWER MAIN RELAY HA ZARD S W A/C CONTROL
ASSEMBLY A/T INDICATOR LIGHT
(
FOR SHIFT LEVER )
SEAT HEATER SW TRACTION CUT SW AND
SEAT HEATER SW SHIFT LOCK ECU
3G 8
3F 8
3F 7
3D 10
3D 9
3A 2
1F 6
1K 6 3H
15
3H 14
3H 3
1D 10
1G 3
1G 4
IF
IG 1E
18 3A
1
W±B W±B W±B
W±B
W±B
W±B W±B W±B
W±B W±B
W±B W±B W±B W±B
W±B W±B
W±B W±B
W±B
W±B
W±B
CE NTER AI RB AG
SENSOR ASSEMBLY
I29
W±B
W±B
3G
3
I38 I8 1K 5
WIPER MOTOR
SEAT HEATER RELAY
KICK DOWN SW
THEFT DETERRENT
AND DOOR LOCK ECU
HE ADLIGHT HI RH
HE ADLIGHT HI LH
COMBINATION METER
(
HIGH BEAM )
CRUISE CONTROL SW
[COMB. SW] E3
I1
4
4
1K
12
IE1
11
IH11
CRUISE CONTROL ECU
( GND ) 1J
1
I7
1G1
8
I5 W±B
W±B
W±B
W±B
W±B
W±B
W±B
W±B R
W±B
W±B W±B W±B W±B W±BW±BW±B
W±B W±B W±B
W±B W±B
W±B
W±B
W±B
W±B
W±B W±B
W±B
W±B
IQ1 10
W±B
(E1 )
( E2 )
TILT AND POWER
TELESCOPIC ECU
( GND2 )
W±B ( A/T )
( M/T )
W±B
1H 13
I38
B4
B31
MOO N ROOF CO NTROL
RE LAY
MOON ROOF LIMIT SW
MOO N ROOF MOTOR
MOO N ROOF CO NTROL
SW
PERSONAL LIGHT
VANITY LIGHT LH
VANITY LIGHT RH
PERSONAL LIGHT
VANITY LIGHT RH
VANITY LIGHT LH B3
B1
B1
B2
B
W±B B
W±B
W±B
W±B
W±B
W±B
W±B
W±B W±BW±B
BZ1
4 BZ1
5
B
W±B
W±B
( CANADA )
W±B
( W/O MOON ROOF )(
W/ MOON ROOF )
(
W/O MEMORY MIRROR )
W±B
(
CANADA )
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239
*2 : W/O DRIVING POSITION MEMORY
* 1 : W/ DRIVING POSITION MEMORY
TILT AND POWER
TELESCOPIC
ECU
(
ECUE )
RECLINING POS ITIO N
SENSOR
[POWER SEAT MOTOR]
SLIDE P OSITION
SENSOR LH
POWER SEAT
CONTROL SW
( FOR DRIVER' S SEAT )
FRONT VARTICAL
POSITION SENSOR
REAR VARTICAL
POSITION SENSOR
POWER SEAT ECU
( FOR DRIVER' S SEAT )
COMBINATION
METER (
E2 ) I5
B28
B26 B27 B 8 Ba213 BT1
13
IF2 13
BU1
6
IH
POWER SEAT ECU
( FOR DRIVER' S SEAT )
POWER SEAT
CONTROL SW
( FOR DRIVER' S SEAT )
SEAT HEATER LH
( FOR DRIVER' S
SEAT BACK )
BUCKLE SW LH
FUEL SENDER
FUEL P UM P
FUEL PUMP ECU AUTO ANTENNA
MOTOR
LIGHT FAILURE
SENSOR LUGGAGE COMPARTMENT
KEYUNLOCKSW
LICENCE PLATE LIGHT
REAR COMB. LIG HT
LH
RE AR COMB. LIGHT
RH
B26 B27
B13 I 22 B14
B15
BK BM
Ba1
12
Ba2
5
BR±B
BR±B
BR±B
BR±B
BR±B
BR±B
BR±B
BR±B
BR BR±B
BR±B
BR±B BR±B BR±B
W±B
W±B W±B
W±B W±B
W±B
W±B
W±B W±B
W±B W±B
W±B
W±B W±B
W±B
W±B
W±B
W±B
W±B
BR±B
BR±B
BR±B
BR
W±B W±B
(
GND )
( GND2 )(
W/ MEMORY )
( W/ MEMORY )
W±B
DRIVING POSITION
MEMORY AND RETURN SW
(*1)
( * 2)
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OVERALL ELECTRICAL WIRING DIAGRAM
1234
4 LEXUS SC300
1J
7 221J
81B2
4
1B
5
1B
4 1K
11
22
22
44
1I 1E
3
4
1 2 23
1
5
4
ACC
IG1
ST1
AM1 3
2
1 21
2 1
21
2
19 IE1 12 IE1 5IE1 6IE1
9IG1
4
7
6 4
19 15
1
3 20 16
2
18 4
97 313
6 7
IJ 1J
5
3A 1E 1C
1A
1I
15
1C
1F
1K 3D
7B 1A
2 1 9
10
BK IF 1H
1K 1J 1E W± BY Y
G± O G
G
W± L
Y
Y
W± B
R± Y
W± G
G± W
W± LW± L
W± L W
W± B R± W
W± B
R
L±W P± B
G±L
R± W
R± W
BR± W
B±L
B±L
W±B
W± B
W±B W±B W±B
W±B W±B
R± W
R± W
R± WR± W
R± W R±B R±B
W
G± W
G± W W
P±L
W± L
G G
P±L
B±Y
W
R± Y R±L R
YVPower
Source
F9
FUSE BL OCK60A MAIN 100A AM1
120A ALT
W
R±Y
40A
IGSW
LO
HI
HI
LO
HEADLIGHT LH
HEADLIGHT RH
HEADLIGHT
RELAY
Fr om Connerring Light
Relay< 7±2> DI ODE10A DOME
7. 5A RADIO No. 2
LIGHT
CONTROL
DIMMER
OFF
TAIL
HEAD
LOW
HIGH
FLASH HU HF FL E D T H E L
C15
COMBINATI ON SW
BATTERY
C13
HIGH BEAM
I NDI CA TOR L I GHT
[COMB. METER]
To Door Lock Mot or and
Unlock Detection SW and
Doo r Open De t ect i on S W LH
<17±5><17±6>
To Door Lock Mot or and
Unlock Detection SW and
Doo r Open De t ect i on S W RH
< 17±6>
From Open Door War ning Light
From Per sonal Light< 6±2>
B4
BACKLE SW LH
I15
UNLOCK WARNI NG SW
[IGNITION SW] SEAT BELT WARNI NG
LI GHT[ COMB. MET ER]
5118
TAIL LIGHT
RELAY
To Thef t
Deter rent and
Do or L oc k ECU
< 17±3>
7. 5A PANEL15A TAIL
10A
GAUGE
3 12 2
13 4Y
BELT
H± LP B A CC TRLY I NTB I G
BKL KEY
12 12
9
To Theft Deterr ent and
Door Lock ECU< 17±3>
I15
IGNITION SW
I16
I NTEGRAT I ON REL AY
H
T
G± L
R±G
1 3
2
B±Y
G±O
1C
16DI ODE
1E
1
9
C1 2 , C1 4 AB
6
From Tens ion Reducer
Solenoid LH< 11±7>
Fr om Thef t Deter rent and
Door Loc k ECU< 17±2>
Fr om Day /Night Shift SW< 12±1>
Fr om Tilt and Power Teles copic
ECU< 11±1> Y
Y
B±L
W±B
5C 4C
CC 3 111 12 7
6428 510 GND
INTEGRATI ON RELAY
SEAT BELT
WARNING LIGHT
[COMB. METER]12
3456
10 11 12 13 17 18 19 20 21 12345 6789
14 15 16
17 18
1 2345 6789 10
23
22
21
20
19
15
14
13
12
11 16 C
A
B I16
C12
C1 4
Headlight and Light Auto Turn Off (
for USA ) Unlock and Seat Belt Warning
(
for USA )
(
Cont . ne xt pa ge )
2
1
1I 3
R± YR± Y
C6 C
21
Y
Right kic k panel
Under t he c ent er pillar LH Left k ick panel
IG1
8
15A
HEAD
RH
15A
HE AD
LH
W±B R
R
R
R
R
R 6Ba2
Ba1
11
5Ba2 Ba1
12 (
w/ ME MORY )
( w/ o MEMORY )
(
w/ Me mo r y )
( w/ o Memory )
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