1991 LEXUS SC400 seat memory

PRECAUTIONS
Take care to observe the following precautions when performing inspection\
s or removal and replacement
of body electrical related parts.
1. SRS AIR±BAG SYSTEM

Work must be started approx. 20 seconds after the ignition is set to the Loc\
k position and the negative
(±) terminal cable is disconnected from the battery. (See page AB±2)

When disconnecting any of the connectors in the SRS AIR±BAG system, be su\
re to Lock the ignition
switch and disconnect the battery negative (±) terminal first. Since the connectors are twin \
lock type
connectors, disconnect the connectors only after releasing the first stage lock.

When connecting SRS AIR±BAG system connectors, be sure to lock them secur\
ely. (If the connectors
are not locked securely, the system may not operate when needed.)

Always store the steering wheel pad with the pad surface facing upward. (Stor\
ing the pad with its
metallic surface up may lead to a serious accident if the air bag inflates for s\
ome reason.)

When installing the spiral cable, be sure the vehicle is in the straight ahe\
ad condition and confirm that
the spiral cable is in the neutral position when it is installed. (See pag\
e BE±40)

INFORMATION LABELS (NOTICE) are attached to the periphery of the air bag componen\
ts. Follow
the NOTICE.
2. MICRO COMPUTER PRESET DRIVING POSITION SYSTEM
Power Seat Control System
Power Mirror Control System
Power Tilt and Telescopic Steering System

If the battery negative (±) terminal is disconnected, the preset driv\
ing positions stored in memory are
erased, so be sure to note the positions and reset them after the battery termi\
nal is reconnected.
3. AUDIO SYSTEM

If the battery negative (±) terminal is disconnected, the preset AM, F\
M 1 and FM 2 stations stored in
memory are erased, so be sure to note the stations and reset them after the battery terminal is
reconnected.

If the battery negative (±) terminal is disconnected, the ºANTI±\
THEFT SYSTEMº will operate when
the terminal is reconnected, but the radio, tape player and CD player will \
not operate. Be sure to input
the correct ID number so that the radio, tape player and CD player can be o\
perated again.
±
BODY ELECTRICAL SYSTEM PrecautionsBE±7
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Steering Wheel Pad (Airbag and Inflator)
Junction Block No. 1 Center Airbag
Front Airbag Sensor
Front Airbag Sensor
Warning Light Spiral Cable (in Combination Switch)
HANDLING PRECAUTIONS ON RELATED COMPONENTS
1. SRS AIRBAG
Locations of Airbag Components
This vehicle has an SRS AIRBAG (referred to as the airbag in the remain\
der of this manual).
When handling airbag components (removal, installation or inspection, e\
tc.), always follow the directions
given in the repair manual for the relevant model year to prevent the oc\
currence of accidents and airbag
malfunction.
Also take the following precautions when repairing the body:

Work must be started after 20 seconds or longer from the time the ignitio\
n switch is set to the LOCK
position and the negative (-) terminal cable is disconnected from the \
battery.
(The airbag system is equipped with a back-up power source so that if w\
ork is started within 20 seconds
of disconnecting the negative (-) terminal cable of the battery, the airbag may be deployed.)
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 outsi\
de 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.
To avoid erasing the memory of each memory system, never use back-up powe\
r supply from outside
the vehicle.

When using electric welding, first disconnect the airbag connector (yel\
low color and 2 pins) under the
steering column near the combination switch connector before starting wo\
rk.
Sensor Assembly
INTRODUCTIONIN-6
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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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