Lexus SC300 / Lexus SC400. Manual — part 181
Limit Switch Circuit
CIRCUIT DESCRIPTION
Slide neutral limit switch: this switch is on when passenger’s seat is slided approx. 120 or more from the most
back position.
Reclining from limit switch: this switch is on, when passenger’s seat back is reclining forward.
Reclining rear limit switch: when passenger’s seat back returns to upright, this is on.
DIAGNOSTIC CHART
DIAGNOSTIC CHART
For each symptom, inspect the circuit indicated in the table.
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Symptom
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Inspection circuit
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•
Only return operation is not functioning.
•
Seat returns to rear most position during return operation.
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Slide neutral limit switch.
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•
Walk–in function and return function do not operate.
(However, they operate when using the manual switch).
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Reclining front limit switch.
Reclining rear limit switch.
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•
Only walk–in operation is not functioning.
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Reclining front limit switch.
Check limit switch.
Check and replace ECU.
Check harness and connector between ECU
and limit switches, limit switches and SGND.
Check continuity between terminals SGND
of ECU connector and body ground.
Check voltage between terminals SLSW,
RFSW, RRSW and SGND of ECU connector.
Proceed to next circuit inspection
shown on matrix chart
(See page
).
Repair or replace harness
connector.
Replace the limit switch.
Repair or replace harness or
connector.
OK
NG
NG
NG
NG
OK
OK
OK
BE–340
–
BODY ELECTRICAL SYSTEM
Power Seat Control System (Passenger’s Seat)
NG
OK
OK
NG
INSPECTION PROCEDURE
1
Check voltage between terminals SLSW, RFSW, RRSW and SGND of ECU connector.
C
OK
P
Remove ECU with connector still connected.
Measure voltage between each terminal and SGND of
ECU connector.
When each limit switch is on and off.
Switch condition
Condition
Voltage
Slide neutral
limit switch
Reclining front
limit switch
Reclining rear
limit switch
ON
OFF
ON
OFF
ON
OFF
Seat is forward of the
neutral position.
Seat is to the rear of
the neutral position.
Seat back is fully reclined.
Others
Seat back is in the upright
position
Others
Below 1 V
10 – 14 V
Below 1 V
Below 1 V
10 – 14 V
10 – 14 V
Proceed to next circuit inspection shown on matrix chart
(See page
2
Check continuity between terminal SGND of ECU connector and body ground.
C
OK
P
Remove ECU with connector still connected.
Measure resistance between SGND of ECU connector
and body ground.
Resistance:
1
or less
Repair or replace harness or connector.
Go to step [3].
–
BODY ELECTRICAL SYSTEM
Power Seat Control System (Passenger’s Seat)
BE–341
OK
NG
OK
NG
WIRING DIAGRAM
3
Check each limit switch.
C
OK
P
Disconnect limit switch connector.
Check continuity of each terminal of limit switch.
Switch condition
Condition
Voltage
Slide neutral
limit switch
Reclining front
limit switch
Reclining rear
limit switch
ON
OFF
ON
OFF
ON
OFF
Seat is forward of the
neutral position.
Seat is to the rear of
the neutral position.
Seat back is fully reclined.
Others
Seat back is in the upright
position
Others
Continuity
Open
Continuity
Continuity
Open
Open
Replace the limit switch.
4
Check for open and short in harness and connector between ECU and limit switches, limit
switches and SGND (See page
Repair or replace harness or connector.
Check and replace ECU.
BE–342
–
BODY ELECTRICAL SYSTEM
Power Seat Control System (Passenger’s Seat)
WIRING DIAGRAM
Reclining Switch and Motor Circuit
CIRCUIT DESCRIPTION
When the power seat switch is turned to forward reclining, the seat back returns to upright.
When the switch is turned to rear reclining, the seat back reclines.
DIAGNOSTIC CHART
DIAGNOSTIC CHART
Check power seat switch.
Check voltage between terminals B1 and
E1 of power seat switch.
NG
Check and repair harness and
connectors between battery and
power seat switch, power seat
switch and body ground.
NG
NG
OK
OK
OK
Check reclining motor.
Check and repair harness and connectors
between switch and motor.
Replace power seat switch.
Replace reclining motor.
BE–344
–
BODY ELECTRICAL SYSTEM
Power Seat Control System (Passenger’s Seat)
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