1991 LEXUS SC400 wiring

WIRING DIAGRAM
CIRCUIT INSPECTION
Parking Brake Switch Circuit
CIRCUIT DESCRIPTION
When the parking brake is operating, the parking brake switch sends a signal\
to the ECU. When this signal
is input to the ECU during tilt & telescopic, the ECU cancels tilt & tel\
escopic.
DIAGNOSTIC CHARTDIAGNOSTIC CHART
SR±96±
STEERING STEERING COLUMN
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SR±52).
WIRING DIAGRAM
Door Courtesy Switch Circuit
CIRCUIT DESCRIPTION
The ECU determines the position of the driver's door by monitoring the voltage at terminal DSW.
 

Door Position 

Switch Position 

DSW Voltage
 Opened Closed Below 1 V
 Closed Opened 10±14 V
DIAGNOSTIC CHARTDIAGNOSTIC CHART
SR±98±
STEERING STEERING COLUMN
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ELECTRONIC CONTROL COMPONENTS
INSPECTION
SOLENOID VALVE
SR0GU±01
1. DISCONNECT WIRING CONNECTOR
2. MEASURE RESISTANCEMeasure the resistance between SOL
and SOL .
Resistance:
6.0±11.0

3. CHECK SOLENOID OPERATION
(a) Connect the battery positive terminal to the solenoid terminal
SOL
.
(b) C onnect the battery negative terminal to the solenoid
terminal SOL .
(c) Check that the solenoid is clicked. If faulty, replace the pressure control valve with the solenoid
valve.
NOTICE:
w Do not apply voltage for more than 30 seconds to avoid
burning out the solenoid.
w If repeating this step, wait until the solenoid cools down
enough that it can be touched by hand.
4. CONNECT WIRING CONNECTOR
±
STEERING POWER STEERINGSR±167
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4. CENTER SPIRAL CABLE
(a) Check that the front wheels are facing straight ahead.
(b) Turn the spiral cable counterclockwise by hand until it
becomes harder to turn the cable.
(c) Then rotate the spiral cable clockwise about 3 turns to align the red mark.
HINT: The spiral cable will rotate about 3 turns to either left
or right of the center.
5. INSTALL STEERING WHEEL
(a) Align matchmarks on the steering wheel and main shaft, and install the wheel to the shaft.
(b) Tighten the wheel set nut.
Torque: 35 N Vm (360 kgf Vcm, 26 ft Vlbf)
(c) Connect the connector.
6. INSTALL STEERING WHEEL PAD
(a) Connect the Airbag connector.
(b) Install the pad after confirming that the circumference groove
of the torx screws is caught on the screw case.
(c) Using a torx wrench, tighten the 4 torx screws.
Torque: 7.4 N Vm (75 kgf Vcm, 65 in. Vlbf)
NOTICE:
w Make sure the wheel pad is installed to the specified
torque.
w If the wheel pad has been dropped, or there are cracks,
dents or other defects in the case or connector, replace
the wheel pad with a new one.
w When installing the wheel pad, take care that the wiring
does not interfere with other parts and is not pinched
between other parts.
7. CHECK STEERING WHEEL CENTER POINT
8. CONNECT NEGATIVE (±) TERMINAL CABLE TO
BATTERY
±
STEERING STEERING COLUMNSR±11
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WIRING DIAGRAM
TILT & TELESCOPIC ECU
SR±46±
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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STANDARD VALUE OF ECU TERMINAL
 

Terminals
 

Symbols
 


Wiring
Color 

Condition
 


Standard
Value
 T9±17 eT9±5 Vc eE1 R±W eBR Unlock warning switch ON 4±6 V
 T9±17eT9±5 VceE1 R±WeBR Unlock warning switch OFF Below 1 V
 T9±18 ECU±B R Always 10 ~ 14 V
 T10±1 e IGe B±R e Ignition switch ON 10 ~ 14 V
 
T10 1 e
Body Ground 
IGe
Body Ground 
BR e
Body Ground Ignition switch OFF Below 1 V
 

T10±2
e
Body Ground
 

Te M+e
Body Ground
 

L±B
e
Body Ground
 


Unlock warning switch ON, telescopic
forward 

10 ~ 14 V
 Body Ground Body Ground Body Ground Except above mention Below 1 V
 T10±3
e TiM±e R±Le Unlock warning switch ON, tilt down 10 ~ 14 V
 
T10 3 e
Body Ground 
TiMe
Body Ground 
RLe
Body Ground Except above mention Below 1 V
 T10±4 +B L±W Always 10 ~ 14 V
 T10±6 e Pe GR e Ignition switch ON, shift lever ªPº position 10 ~ 14 V
 
T10 6 e
Body Ground 
Pe
Body Ground 
GR e
Body Ground Ignition switch ON, except above mention Below 1 V
 T10±6 e Pe GR e Ignition switch ON, PKB lever pulled Below 1 V
 
T10 6 e
Body Ground 
Pe
Body Ground 
GR e
Body Ground Ignition switch ON, PKB lever released 10 ~ 14 V
 T10±7 GND W±B Always Below 1 V
 T10±10 e TiM+e R±Be Unlock warning switch ON, tilt up 10 ~ 14 V
 
T10 10 e
Body Ground 
TiMe
Body Ground 
RBe
Body Ground Except above mention Below 1 V
 T10±11 e
Body Ground
 Te M±e
Body Ground
 L±Ye
Body Ground
 Unlock warning switch ON, telescopic
backward 10 ~ 14 V
 Body Ground Body Ground Body Ground Except above mention Below 1 V
TILT & TELESCOPIC ECU
SR±50±
STEERING STEERING COLUMN
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SR±52).
IN±33).
WIRING DIAGRAM
CIRCUIT INSPECTION
ECU Power Source Circuit
CIRCUIT DESCRIPTION
The ECU power source also supplies power to the CPU and sensor, etc. Power is supplied to the ECU even
when the ignition switch is off.
DIAGNOSTIC CHARTDIAGNOSTIC CHART
SR±62±
STEERING STEERING COLUMN
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