LEXUS SC400 1991 Service Repair Manual

±MEMO±
±
STEERING STEERING COLUMNSR±69
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SR±52).
WIRING DIAGRAM
Sensor Power Source Circuit
CIRCUIT DESCRIPTION
Power to the position sensors, manual switch and auto set switch is output fr\
om the ECU.
DIAGNOSTIC CHARTDIAGNOSTIC CHART
SR±70±
STEERING STEERING COLUMN
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OKNG
OKNG
OKNG
INSPECTION PROCEDURE
1Check voltage between terminals VC and E1 of ECU connector.
C
OK
PRemove ECU with connectors still connected.
Measure voltage between terminals V
C and E1 of ECU
connector.
Voltage: 4 ± 6 V
Go to Step
.
2Check for open in harness and connector between terminals Vc and E1 of ECU connector.
Repair or replace harness or connector.
Proceed to next circuit inspection shown on ma-
trix chart (See page SR±52).
3Check for short in harness between terminal VC and E1 of ECU connector.
Repair or replace harness or connector.
Check and replace ECU.
±
STEERING STEERING COLUMNSR±71
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SR±52).
IN±33).
WIRING DIAGRAM
Tilt Position Sensor Circuit
CIRCUIT DESCRIPTION
The tilt position is sent to the ECU as a voltage signal from the position \
sensor.
A constant 5 V is supplied to terminal 1 of sensor.
The voltage at terminal 3 varies with position and is input to the ECU.
DIAGNOSTIC CHARTDIAGNOSTIC CHART
SR±72±
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NGOK
OKNG
OKNG
INSPECTION PROCEDURE
1Check voltage between terminals TiS and E1 of ECU connector.
C
OK
Hint
P1. Remove ECU with connectors still connected.
2. Remove tilt sensor with connector still connected.
Measure voltage between terminals TiS and E
1 of ECU
connector, while turning tilt sensor lever slowly by hand
from raised side to lowered side.
Voltage:
Fully raised: Below 1 V
Fully lowered: 4 ± 6 V
In addition, as the lever is turned, the voltage should
increase gradually without interruption.
Proceed to next circuit inspection shown on matrix chart
(See page SR±52).
2Check tilt position sensor.
C
OK
Hint
PDisconnect tilt sensor connector.
Measure resistance between terminals 1 and 2 of tilt
sensor connector.
Resistance: 4 ± 6

Measure resistance between terminals 3 and 2 of tilt
sensor connector, while turning tilt sensor lever slowly
by hand from raised side to lowered side.
Resistance:
Fully raised: Below 100

Fully lowered: 4 ± 6

In addition, as the lever is turned, the resistance
should increase gradually without interruption.
Replace tilt position sensor.
3Check harness and connectors between ECU and tilt position sensor (See \
page IN±33).
Repair harness or connector.
Check and replace ECU.
±
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SR±52).
IN±33).
WIRING DIAGRAM
Telescopic Position Sensor Circuit
CIRCUIT DESCRIPTION
The telescopic position is sent to the ECU as a voltage signal from the pos\
ition sensor.
A constant 5 V is supplied to terminal 6 of the sensor.
The voltage at terminal 5 varies with position and is input to the ECU.
DIAGNOSTIC CHARTDIAGNOSTIC CHART
SR±76±
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NGOK
OKNG
OKNG
INSPECTION PROCEDURE
1Check voltage between terminals TeS and E1 of ECU connector.
C
OK
P1. Remove ECU with connectors still connected.
2. Remove telescopic sensor with connectors stillconnected.
Measure voltage between terminals TeS and E
1 of ECU
connector while turning telescopic sensor lever slowly
by hand from Contracted side to Extended side.
Voltage:
Fully forward: 0 ± 1 V
Fully back: 4 ± 5 V
In addition, as the lever is turned, the voltage should
increase gradually without interruption.
Proceed to next circuit inspection shown on matrix chart
(See page SR±52).
2Check telescopic position sensor.
C
OK
P
OK
C
Disconnect telescopic sensor connector.
Measure resistance between terminals 3 and 6 of tele-
scopic sensor connector.
Resistance: Approx. 5 k

Measure resistance between terminals 3 and 5 of tele-
scopic sensor connector while turning telescopic lever
slowly by hand from Contracted side to Extended side.
Resistance:
Fully forward: 0 ± 1

Fully back: 4 ± 5

In addition, as the lever is turned, the resistance
should increase gradually without interruption.
Replace tilt position sensor.
3Check harness and connectors between ECU and tilt position sensor (See \
page IN±33).
Repair harness or connector.
Check and replace ECU.
±
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SR±52 ).
IN±33 ).
WIRING DIAGRAM
Telescopic Motor Circuit
CIRCUIT DESCRIPTION
The ECU provides both + B and ground for the telescopic motor.
Reversing polarity of the applied voltage reverses the motor.
 Te M+ Te M± Rotation Telescopic
 

+ 

± 

Clockwise 

Contracted
 ± + Counterclockwise Extended
DIAGNOSTIC CHARTDIAGNOSTIC CHART
SR±78±
STEERING STEERING COLUMN
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OKNG
OKNG
INSPECTION PROCEDURE
1Check telescopic motor.
C
PDisconnect telescopic motor connector.
Connect positive (negative ) terminal to terminal
1 of telescopic motor connector and negative  (posi-
tive ) terminal to terminal 2.
Replace telescopic motor.
2Check harness and connector between ECU and telescopic motor (See page \
IN±33).
Repair or replace harness or connector.
Proceed to next circuit inspection shown on ma-
trix chart (See page SR±52).
±
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SR±52).
IN±33 ).
WIRING DIAGRAM
Auto Set Switch Circuit
CIRCUIT DESCRIPTION
This is the main switch for auto operation.
When the switch is off, auto operation is prohibited.
DIAGNOSTIC CHARTDIAGNOSTIC CHART
SR±80±
STEERING STEERING COLUMN
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