ECU LEXUS SC400 1991 Service Repair Manual

WIRING DIAGRAM
TILT & TELESCOPIC ECU
SR±46±
STEERING STEERING COLUMN
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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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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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HINT

If the instruction ªProceed to next circuit inspection shown on matrix chartº is given in the flo\
w chart
for each circuit, proceed to the circuit with the next highest number in th\
e table to continue the check.

If the trouble still reappears even through there are no abnormalities i\
n any of the other circuits, then
check and replace the Tilt & Telescopic ECU as the last step.
SR±76
SR±76
SR±80 SR±84
SR±88 SR±90
SR±92
SR±94
SR±96
SR±98
SR±100
IN±38
±
STEERING STEERING COLUMNSR±53
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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±
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NGOK
OKNG
INSPECTION PROCEDURE
1Check voltage between terminals ECU±B and ECU±E of ECU connector.
C
OK
PRemove ECU with connectors still connected.
Measure voltage between terminals ECU±B and ECU±
E of ECU connector.
Voltage: 10 ~ 14 V
Proceed to next circuit inspection shown on matrix chart
(See page SR±52).
2Check continuity between terminal ECU±E of ECU connector and body gro\
und.
C
OK
Measure resistance between terminal ECU±E of ECU
connector and body ground.
Resistance: 1
or less
Repair or replace harness or connector.
Go to Step
.
±
STEERING STEERING COLUMNSR±63
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OKNG
3Check DOME Fuse.
C
OK
PRemove DOME Fuse from R/B No. 2.
Check continuity of DOME Fuse.
Continuity
Check for short in all the harness and components con-
nected to DOME Fuse (See attached wiring diagram).
Check harness and connector between ECU and
battery (See page
IN±33).
SR±64±
STEERING STEERING COLUMN
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FRONT AIRBAG SENSOR
RS00N±07
1. Never reuse the front airbag sensor involved in a collision when the airbag h\
as deployed. (Replace boththe left and right airbag sensors.)
2. Install the front airbag sensor with the arrow on the sensor facing towa\
rd the front of the vehicle.
3. The front airbag sensor set bolts have been anti±rust treated. When the \
sensor is removed, always replace
the set bolts with new ones.
4. The front airbag sensors is equipped with an electrical connection check me\
chanism. Be sure to lock this mechanism securely when connecting the connector. If the connector is not securely locked, a malfunction
code will be detected by the diagnosis system (See page RS±12).
CENTER AIRBAG SENSOR ASSEMBLY
RSOOR±0A
1. Never reuse the center airbag sensor assembly involved in a collision when the airbag has
deployed.
2. Work must be started after 90 seconds from the time the ignition switch is t\
urned to LOCK position and the negative (±) terminal cable is disconnected from the batter\
y even just loosing the set bolts
of center airbag sensor assembly.
WIRE HARNESS AND CONNECTOR
RSO41±01
The SRS wire harness is integrated with the cowl wire harness assembly. The wires for the SRS wire har-
ness are encased in a yellow corrugated tube. All the connectors for the sys\
tem are also a standard yellow
color. If the SRS wire harness becomes disconnected or the connector becomes broken du\
e to an accident
etc., repair or replace it as shown on page RS±48.
±
SUPPLEMENTAL RESTRAINT SYSTEM GENERAL DESCRIPTIONRS±5
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(1) Terminal Twin±Lock MechanismEach connector has a two±piece construction consisting of
a housing and a spacer. This design secures the locking of
the terminal by two locking devices (the spacer and the lance)
to prevent terminals from coming out.
(2) Airbag Activation Prevention Mechanism Each connector contains a short spring plate. When the con-
nector is disconnected, the short spring plate automatically
connects the power source and grounding terminals of the
squib.
HINT: The illustration shows connectors ,  and  . Con-
nector

has short spring plates on the female terminal side.
±
SUPPLEMENTAL RESTRAINT SYSTEM OPERATIONRS±11
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