sensor LEXUS SC400 1991 Service Repair Manual

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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HOW TO PROCEED WITH TROUBLESHOOTING
Perform troubleshooting in accordance with the procedure on the following page.\

CUSTOMER PROBLEM ANALYSIS
Using the customer problem analysis check sheet for reference, obtain as much detail as possible about
the problem.
 PROBLEM SYMPTOM CONFIRMATION,  SYMPTOM SIMULATION
Confirm the problem symptoms. If the problem does not reappear, be sure to simulate the problem, using
the ªProblem Simulation Methodsº.
 MATRIX CHART OF PROBLEM SYMPTOMS
Confirm the order of inspection for each applicable problem symptom on t\
he matrix chart after first fully
confirming the scope of the problem symptoms. For example, if the tilt operation i\
s not working, check
whether the tilt is not working in manual, auto and return, and also check if the telescopic, seat or mirror
operation is not working in addition to the tilt operation.
 CIRCUIT INSPECTION
Proceed with diagnosis of each circuit in accordance with the inspection order \
confirmed in . Judge
whether the cause of the problem is in the sensor, actuators, wire harness and connectors, or the ECU.
6 REPAIR
After the cause of the problem is located, perform repairs by following the i\
nspection and replacement pro-
cedures in this manual.
7 CONFIRMATION TEST After completing repairs, confirm not only that the malfunction is eliminated,\
but also seat and mirror opera-
tions are normal.
SR±45
SR±52
SR±62 ~ SR±101 IN±26
SR±44
±
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
±
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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DTC53Short in Squib Circuit (Between P+ Wire Harness
P
± Wire Harness)
CIRCUIT DESCRIPTION
The squib circuit consists of the center airbag sensor assembly, (squib). It causes the SRS to deploy when the
SRS deployment conditions are satisfied.
For details of the function of each component, see FUNCTION OF COMPONENTS o\
n page RS±10. Diagnostic
trouble code 53 is recorded when an short is detected in the P
+ wire harness and P± wire harness of the squib
circuit.
DTC No.Diagnosis
53
 Short circuit between P+ wire harness and P± wire harness of squib.
 Squib malfunction.
 Center airbag Sensor Assembly malfunction.
DIAGNOSTIC CHARTDIAGNOSTIC CHART
RS±110±
SUPPLEMENTAL RESTRAINT SYSTEM TROUBLESHOOTING
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OKNG
INSPECTION PROCEDURE
1Preparation.
P1. Disconnect battery negative (±) terminal cable, andwait at least 90 seconds.
2. Remove steering wheel pad (See page RS±19).
3. Disconnect connectors of front passenger airbag assembly (See page RS±32).
Caution: Store the steering wheel pad with the
surface facing upward.
2Check P squib circuit.
C
OK
Measure resistance between P+ and P± on center air-
bag sensor assembly side of connector between center
airbag sensor assembly and front passenger airbag as-
sembly.
Resistance: 1 k
or higher
Go to step
.
RS±112
±
SUPPLEMENTAL RESTRAINT SYSTEM TROUBLESHOOTING
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OKNG
OKNG
3Check center airbag sensor assembly.
C
OK
Hint
P1. Connect negative (±) terminal cable to battery.
2. Clear malfunction code stored in memory. (Seepage RS±63 ).
1. Turn ignition switch LOCK, and wait at least 20 sec- onds.
2. Using a service wire, connect D
+ and D±, P+ and P±.
3. Turn ignition switch ACC or ON, and wait at least 20 seconds.
4. Using SST, connect terminals Tc and E
1 of DLC2.
SSt 09843±18020
5. Check diagnostic trouble code.
Diagnostic trouble code 53 is not output.
Codes other t han code 53 may be output at this time, but
this is not relevant to this check.
Replace center airbag sensor assembly.
4Check P squib.
C
OK
Hint
P1. Turn ignition switch LOCK.
2. Disconnect battery negative (±) terminal cable, and
wait at least 90 seconds.
3. Connect front passenger airbag assembly connec- tor.
4. Connect negative (±) terminal cable to battery.
5. Clear malfunction code.
1. Turn ignition switch LOCK, and wait at least 20 sec- onds.
2. Turn ignition switch ACC or ON, and wait at least 20 seconds.
3. Using SST, connect terminals Tc and E
1 of DLC2.
SST 09843±18020
4. Check diagnostic trouble code.
Diagnostic trouble code 53 is not output.
Codes other t han code 53 may be output at this time, but
this is not relevant to this check.
Replace front passenger airbag assembly.
±
SUPPLEMENTAL RESTRAINT SYSTEM TROUBLESHOOTINGRS±113
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OKNG
OKNG
From the results of the above inspection, the malfunctioning part can now be\
considered normal. To
make sure of this, use the simulation method to check.
5Check P circuit.
C
OK
P1. Disconnect center airbag sensor assembly con-nector.
2. Release airbag activation prevention mechanism on center airbag sensor assembly connector (See
page RS±91 ).
Measure resistance between P
+ and P± on center air-
bag sensor assembly side of connector between airbag
sensor assembly and front passenger airbag assembly.
Resistance: 1 M
of higher
Repair or replace harness or connector between center
airbag sensor assembly and front passenger airbag as-
sembly.
6Check center airbag sensor assembly.
C
OK
PConnect center airbag sensor assembly connector.
Measure resistance between P
+ and P± on center air-
bag sensor assembly side of connector between center
airbag sensor assembly and front passenger airbag as-
sembly.
Resistance: 1 k
or higher
Replace center airbag sensor assembly.
From the results of the above inspection, the malfunction part can now be con\
sidered normal. To make
sure of this, use the simulation method to check.
RS±114±
SUPPLEMENTAL RESTRAINT SYSTEM TROUBLESHOOTING
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DTC54Open in P Squib Circuit
CIRCUIT DESCRIPTION
The squib circuit consists of the center airbag sensor assembly and front p\
assenger airbag assembly. It causes
the SRS to deploy when the SRS deployment conditions are satisfied. For det\
ails of the function of each compo-
nent, see FUNCTION OF COMPONENTS on page RS±10.
Diagnostic trouble code 54 is recorded when an open is detected in the s\
quib circuit.
DTC No.Diagnosis
54

Open circuit in P+ wire harness and P± wire harness of squib.

Squib malfunction.

Center airbag sensor malfunction.
±
SUPPLEMENTAL RESTRAINT SYSTEM TROUBLESHOOTINGRS±115
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OKNG
1Preparation.
P1. Disconnect battery negative (±) terminal cable, andwait at least 90 seconds.
2. Remove steering wheel pad (See page RS±19).
3. Disconnect connectors of front passenger airbag assembly (See page RS±32).
Caution: Store the steering wheel pad with the
surface facing upward.
2Check P squib circuit.
C
OK
PDisconnect center airbag sensor assembly connector.
Measure resistance between P
+ and P± on center air-
bag sensor assembly side of connector between center
airbag sensor assembly and front passenger airbag as-
sembly.
Resistance: Below 1

Repair or replace harness or connector between center
airbag sensor assembly and front passenger airbag as-
sembly.
±
SUPPLEMENTAL RESTRAINT SYSTEM TROUBLESHOOTINGRS±117
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