warning LEXUS SC400 1991 Service Repair Manual

STEERING COLUMN
DESCRIPTION
SR0EA±02
There are two types of steering column, the manual tilt/manual telescopic one\
, and the power tilt/power
telescopic one.
SR0EB±02
OPERATION
POWER TILT OPERATIONThe power tilt mechanism consists of the control gear assembly, tilt motor, tilt position sensor, tilt and tele-
scopic switch, unlock warning switch and tilt and telescopic ECU.
The control gear assembly consists of the worm wheel, tilt gear, tilt worm and slider. Rotation of the tilt motor
moves the slider towards the tilt worm. The column upper tube is integrated w\
ith the slider and is rotated
up and down by movement of the slider.
SR±4
±
STEERING STEERING COLUMN
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POWER TELESCOPIC OPERATION
SR0EC±02
The power telescopic mechanism is composed of the control gear assembly, telescopic motor, telescopic
position sensor, tilt and telescopic switch, unlock warning switch and tilt and telesco\
pic ECU.
The control gear assembly is composed of the worm wheel, telescopic scre\
w and slider. Rotation of the
telescopic motor moves the slider in the direction of the telescopic screw axis. The\
sliding tube is integrated
with the slider and is moved forward and backward by movement of the slider.
±
STEERING STEERING COLUMNSR±5
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TERMINAL OF ECU
TILT & TELESCOPIC ECU
 




Terminal
No.
 




Symbol
 




Terminal Name
 




Terminal
No.
 




Symbol
 




Terminal Name
 T9±1 Si Serial In T9±16 MSW Manual Switch
 2 DSW Door Courtesy Switch 17 Vc Sensor Power Source
 3 M1 Return Switch 1 18 ECU±B Power Source 

4
 

ASW
 

Auto Switch
 

T10± 1
 

IG
 

Ignition Switch
 5 E1 Sensor Ground 2 Te M+ Telescopic Contracted
 6 Te S Telescopic Sensor 3 TiM± Tilt Down
 
7 
TiS 
Tilt Sensor 
4 
+B 
Power Source 

8
 

ECU±E
 

Ground
 

6
 

P
 

Park/Neutral Position Switch
 9 So Serial Out 6 P Parking Brake Switch*
 10 UWSW Unlock Warning Switch 7 GND Ground 

11 

MRY 

Memory Switch 

10 

TiM+ 

Tilt Up
 12 M2 Return Switch 2 11 TiM± Telescopic Extended
*
SC300 (M/T) Models
SR±48
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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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WIRING DIAGRAM
SRS Warning Light System (Always Lit Up, when ignition switch in
LOCK position)
CIRCUIT DESCRIPTION
The SRS warning light is located on the combination meter.
When the supplemental restraint system is normal, the SRS warning light ligh\
ts up for approx. 6 seconds after
the ignition switch is turned from LOCK position to ACC or ON position, and\
then turns off automatically.
If there is a malfunction in the supplemental restraint system, the SRS wa\
rning light lights up to inform the driver
of the abnormality.
When terminals Tc and E
1 of the DLC2 are connected, the diagnostic trouble code is displayed by \
the blinking
of the SRS warning light.
DIAGNOSTIC CHARTDIAGNOSTIC CHART
HINT: If the SRS warning light is always lit up by a DTC check procedure, per\
form Tc T erminal circuit check proce-
dure (See page RS±121).
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SUPPLEMENTAL RESTRAINT SYSTEM TROUBLESHOOTINGRS±119
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YESNO
INSPECTION PROCEDURE
1Does SRS warning light turn off?
C
Hint
P1. Turn ignition switch LOCK.
2. Disconnect negative (±) terminal cable from battery
and wait at least 90 seconds.
3. Remove steering wheel pad (See page RS±19).
4. Disconnect connectors of front passenger airbag assembly (See page RS±32).
5. Disconnect center airbag sensor assembly con- nector.
6. Connect negative (±) terminal cable to battery.
Check operation of SRS warning light.
Ignition Switch is LOCK position.
Check SRS warning light circuit or terminal AB circuit of
DCL1 or DLC2.
Replace center airbag sensor assembly.
RS±120±
SUPPLEMENTAL RESTRAINT SYSTEM TROUBLESHOOTING
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Tc Terminal Circuit
CIRCUIT DESCRIPTION
By connecting terminal Tc and E1 of the DLC1 or DLC2, the center airbag sensor assembly is set in the di\
agnos-
tic trouble code output mode. The diagnostic trouble codes are displayed\
by the blinking of the SRS warning
light.
DIAGNOSTIC CHARTDIAGNOSTIC CHART
Troubleshooting for this system is different depending on whether the diagnostic trouble code is not displayed\
SRS warning light is always lit up with a DTC check procedure, or is displa\
yed without a DTC check procedure.
Confirm the problem symptoms first before selecting the appropriate troubleshoo\
ting procedure.
HINT: If the diagnostic trouble code is not displayed or SRS warning light is\
always lit up with a DTC check proce-
dure perform the following troubleshooting:
±
SUPPLEMENTAL RESTRAINT SYSTEM TROUBLESHOOTINGRS±121
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NGOK
3Check center airbag sensor assembly.
C
OK
P1. Turn ignition switch LOCK.
2. Disconnect battery negative (±) terminal cable, andwait at least 90 seconds.
3. Remove steering wheel pad (See page RS±19).
4. Disconnect connectors of front passenger airbag assembly (See page RS±32).
Check operation of SRS warning light.
SRS warning light comes on.
Check harness between center airbag sensor assembly
and DLC1 or DLC2.
Replace center airbag sensor assembly.
RS±124±
SUPPLEMENTAL RESTRAINT SYSTEM TROUBLESHOOTING
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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
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SUPPLEMENTAL RESTRAINT SYSTEM GENERAL DESCRIPTION
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