LEXUS SC400 1991 Service Repair Manual

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 mostback 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 CHARTDIAGNOSTIC CHART
For each symptom, inspect the circuit indicated in the table.
\
 \
Symptom Inspection circuit
\
 
\

\

w
Only return operation is not functioning.
w Seat returns to rear most position during return operation. 

Slide neutral limit switch.
\
 
\

\

w
Walk±in function and return function do not operate.
(However, they operate when using the manual switch). 


Reclining front limit switch.
Reclining rear limit switch.
\
 \
w
Only walk±in operation is not functioning. 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
BE±319).
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)
WhereEverybodyKnowsYourName

NGOK
OKNG
INSPECTION PROCEDURE
1Check voltage between terminals SLSW, RFSW, RRSW and SGND of ECU connector.
C
OK
PRemove 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 BE±319).
2Check continuity between terminal SGND of ECU connector and body ground.\
C
OK
PRemove 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
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OKNG
OKNG
WIRING DIAGRAM
3Check each limit switch.
C
OK
PDisconnect 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 switc\
hes, limit
switches and SGND (See page IN±27).
Repair or replace harness or connector.
Check and replace ECU.
BE±342±
BODY ELECTRICAL SYSTEM Power Seat Control System (Passenger's Seat)
WhereEverybodyKnowsYourName

WIRING DIAGRAM
Reclining Switch and Motor Circuit
CIRCUIT DESCRIPTION
When the power seat switch is turned to forward reclining, the seat back ret\
urns to upright.
When the switch is turned to rear reclining, the seat back reclines.
DIAGNOSTIC CHARTDIAGNOSTIC CHART
Check power seat switch.
Check voltage between terminals B1 and
E1 of power seat switch.
NGCheck 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)
WhereEverybodyKnowsYourName

OKNG
OKNG
INSPECTION PROCEDURE
1Check voltage between terminals B1 and E1 of power seat switch.
C
OK
PRemove power seat switch with connector still con-
nected.
Measure voltage between terminals B1 and E1 of power
seat switch connector.
Voltage: 10 ± 14 V
Check and repair harness and connectors between bat-
tery and power seat switch, power seat switch and body
ground.
2Check power seat switch.
C
OK
PDisconnect power seat switch connector.
Check continuity of each terminal shown below.
Switch Position
Terminal
Reclining
Neutral
Forward
Back
1625
Continuity
Replace power seat switch.
Go to step [3].
±
BODY ELECTRICAL SYSTEM Power Seat Control System (Passenger's Seat)BE±345
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OKNG
3Check reclining motor.
C
OK
P
OK
C
(1) Remove seat.
(2) Disconnect reclining motor connector.
Connect battery
to terminal 1, and battery  to termi-
nal 2 of the reclining motor connector.
The seat back reclines.
Connect battery  to terminal 1, and battery
to termi-
nal 2 of the reclining motor connector.
The seat back returns to upright.
Replace reclining motor.
Check and repair harness connectors between
switch and motor.
BE±346±
BODY ELECTRICAL SYSTEM Power Seat Control System (Passenger's Seat)
WhereEverybodyKnowsYourName

DOOR LOCK CONTROL SYSTEM
±
BODY ELECTRICAL SYSTEM Door Lock Control SystemBE±361
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DESCRIPTION
The door lock control system has a key±interlocked door lock and unlock \
function and a key±confinement pre-
vention function. All doors can be locked and unlocked simultaneously by\
key operation at the front right or left
door (the key needs to be operated twice to unlock the doors at the driver's door). If the door lock operation is
performed when one of the doors is open and the ignition key inserted in\
the key cylinder, doors are unlocked
automatically to prevent the ignition key from being left inside the veh\
icle. The luggage compartment door can
be opened by electromagnetic opener.
For the function of component parts of this system, refer to the circuit\
description in circuit inspection.
PARTS LOCATION
BE±362±
BODY ELECTRICAL SYSTEM Door Lock Control System
WhereEverybodyKnowsYourName

DESCRIPTION
The door lock control system has a key±interlocked door lock and unlock f\
unction and a key±confinement pre-
vention function. All doors can be locked and unlocked simultaneously by\
key operation at the front right or left
door (the key needs to be operated twice to unlock the doors at the driver's door). If the door lock operation is
performed when one of the doors is open and the ignition key inserted in\
the key cylinder, doors are unlocked
automatically to prevent the ignition key from being left inside the veh\
icle. The luggage compartment door can
be opened by electromagnetic opener.
For the function of component parts of this system, refer to the circuit\
description in circuit inspection.
PARTS LOCATION
BE±362±
BODY ELECTRICAL SYSTEM Door Lock Control System
WhereEverybodyKnowsYourName

±MEMO±
±
BODY ELECTRICAL SYSTEM Door Lock Control SystemBE±363
WhereEverybodyKnowsYourName