ECU LEXUS SC400 1991 Service Repair Manual

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)
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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, ask the c\
ustomer in 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
ºProblem Simulation Methodº.
For example, if the malfunction involves failure of the lock or unlock duri\
ng operation of the Door Lock Con-
trol Switch, check if lock and unlock operation of the door using the key is\
normal or abnormal, and also
check if key confinement prevention function and luggage compartment door ope\
ner function are normal
or not. And having fully checked the extent of the malfunction.
 MATRIX CHART OF PROBLEM SYMPTOMS
Confirm the order of inspection for each applicable problem symptom on t\
he matrix chart.
 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, wire harness and connectors, or the ECU.
 REPAIR
When the cause of the problem is found in , perform repairs.
 CONFIRMATION TEST
After completing repairs, confirm that the problem is eliminated and that all functions of the door lock control
system are normal.
BE±364
±
BODY ELECTRICAL SYSTEM Door Lock Control System
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TERMINALS OF ECU
 No. Symbol Terminal Name No. Symbol Terminal Name T8±3 ACT ± Door Lock Motor T8±13 DSWD Door Open Detection Switch 

T8±4
 

ACT +
 

Door Lock Motor
 

T8±14
 

L1
 

Door Key Lock and Unlock Switch
(Lock)
 

T8±5
 

TO
 

Luggage Compartment Door Opener
Motor 

T8±15
 

UL1
 

Door Key Lock and Unlock Switch
(Unlock)
 T8±6 KSW Key Unlock Warning Switch T8±16 E Ground 

T8±7 

LSWP 

Door Unlock Detection Switch 

T8±17 

L2 

Door Lock Control Switch (Lock)
 T8±8 + B2 Actuator Power Source T8±18 UL2 Door Lock Control Switch (Unlock)
 


T8±10 


UL3 


Door Key Lock and Unlock Switch
(Unlock) 


T8±19 


TSW 


Luggage Compartment Door Opener
Switch
 T8±11 LSWD Door Unlock Detection Switch T8±20 + B1 ECU Power Source
 T8±12 DSWP Door Open Detection Switch   
BE±368±
BODY ELECTRICAL SYSTEM Door Lock Control System
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STANDARD VALUE OF ECU TERMINAL
 

Terminals 

Symbols 


Wiring
Color 

Condition 

Standard Value
 T9±3
e T9±4 ACT e ACT+ L±W e L±R Ignition switch OFF 50
or less
 T9±5 e T9±16 T0 e E B e W±B Ignition switch OFF 100
or less
 
T9 6 eT9 16
 
KSW eE
 
Ye WB
 Key unlock warning switch ON.
(Key is inserted into key cylinder). 1
or less
 


T9±6
e T9±16 


KSW
e E 


Y
e W±B 

Key unlock warning switch OFF.
(Key is not inserted into key cylinder). 

1 M

or higher
 

T9±7
e T9±16
 

LSWP
e E
 

P±B
e W±B
 


Door unlock detection switch ON.
(Passenger's) 

1

or less
    Door unlock detection switch OFF. 1 M
higher
 T9±8 e T9±16 +B2 e E L±W e W±B Always 10±14 V
 
T9 10 eT9 16
 
UL3 eE
 
Ge WB
 Door key lock and unlock switch ºunlockº
position. 1
or less
 


T9±10
e T9±16 


UL3
e E 


G
e W±B 

Door key lock and unlock switch OFF or
ºlockº position. 

1 M

or higher
 
T9 11 eT9 16
 
LSWD eE
 
WL eWB
 Door unlock detection switch ON. (driver's) 1
or less
 T9±11 e T9±16 LSWD e E W±L e W±B Door unlock detection switch OFF. (driver's) 1 M
or higher
 

T9 12
eT9 16
 

DSWP
eE
 

RW
eWB
 


Door open detection switch (passenger's)
ON (door opened). 

1

or less
 


T9±12
e T9±16 


DSWP
e E 


R±W
e W±B 


Door open detection switch (passenger's)
OFF (door closed). 


1 M

or higher
 
T9 13 eT9 16
 
DSWD eE
 
RB eWB
 Door open detection switch (driver's)
ON (door opened). 1
or less
 


T9±13
e T9±16 


DSWD
e E 


R±B
e W±B 

Door open detection switch (driver's)
OFF (Door closed). 

1 M

or higher
 

T9 14
eT9 16
 

L1
eE
 

GY
eWB
 


Door key lock and unlock switch ºlockº
position. 

1

or less
 


T9±14
e T9±16 


L1
e E 


G±Y
e W±B 


Door key lock and unlock switch OFF or
ºunlockº position. 


1 M

or higher
 
T9 15 eT9 16
 
UL1 eE
 
GW eWB
 Door key lock and unlock switch ºunlockº
position. 1
or less
 


T9±15
e T9±16 


UL1
e E 


G±W
e W±B 

Door key lock and unlock switch OFF or
ºlockº position. 

1 M

or higher
 


T9±16
e Body
Ground 


E
e Body
Ground 


W±B
e Body
Ground 

Always 

1

or less
    Door lock control switch ªlockº position. 1
or less
 

T9±17 e T9±16 

L2 e E 

R±B e W±B 

Door lock control switch OFF or ªunlockº
position. 

1 M
or higher
    Door lock control switch ªunlockº position 1
or less 

T9±18
e T9±16 

UL2
e E 

G±L
e W±B 

Door lock control switch OFF or ªlockº
position. 

1 M

or higher
±
BODY ELECTRICAL SYSTEM Door Lock Control SystemBE±369
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Terminals Symbols WiringColor Condition Standard Value
 T9±19 e T9±16 TSW e E L e W±B Luggage compartment door opener switch ON. 1
or less 


 


 


 

Luggage compartment door opener switch
OFF. 

1 M

or higher
 T9±20 e T9±16 +B1 e E R e W±B Always 10±14 V
O When checking the voltage or resistance of theft deterrent and door lock\
ECU terminal, disconnect
the ECU connector.
BE±370
±
BODY ELECTRICAL SYSTEM Door Lock Control System
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MATRIX CHART OF PROBLEM SYMPTOMS
Perform troubleshooting of the circuits for the applicable problem symptom in t\
he order given in the chart below.
Proceed to the page located for each circuit.
HINT:
If the instruction ªProceed to next circuit inspection shown on matrix \
chartº is given in the flow chart for each
circuit, proceed to the circuit with the next highest number in the table to con\
tinue the check.

If the trouble still reappears even though there are no abnormalities in a\
ny of the other circuits, then check
or replace the Theft Deterrent and Door Lock ECU as the last step.
See page
BE±376BE±378BE±380BE±382BE±384BE±386BE±388BE±390BE±392IN±32
SymptomSuspect Area
ECU Power Source CircuitActuator Power Source CircuitDoor Lock Motor CircuitLuggage Compartment Door Opener Motor
CircuitDoor Lock Control Switch CircuitDoor key Lock and Unlock Switch CircuitKey Unlock Warning Switch CircuitLuggage Compartment Door Opener Main
Switch and Opener Switch CircuitDoor Open Detection Switch CircuitTheft Deterrent and Door Lock ECU
Whole functions of the door lock control system does notWhole functions of the door lock control system does not
t12435operate.12435
All doors or some doors are not locked and unlocked with theAll doors or some doors are not locked and unlocked with the
Door Lock Control Switch and Key o
perated SwitchDoor Lock Control Switch and Key operated Switch.
(Luggage compartment door opener function normally oper3124(Luggage compartment door opener function normally oper-
t)
3124
ate.)
Doors cannot be locked or unlocked with the door lock con-Doors cannot be locked or unlocked with the door lock con
trol switch. (Doors lock and unlock normally with the key op-1234(yy
erated switch.)
1234
Doors are not locked or unlocked with the key operatedDoors are not locked or unlocked with the key o erated
switch. (Doors lock and unlock normally with the door lock12(y
control switch.)
12
Key confinementprevention function does not operateKey confinement prevention function does not operate.123y
Doors lock and unlock normally with the key o
perated switch123Doors lock and unlock normally with the key operated switch.
Luggage compartment door opener function does not oper-Luggage compartment door opener function does not oper-
t213ate.213
±
BODY ELECTRICAL SYSTEM Door Lock Control SystemBE±371
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Check DOME fuse.NG OKCheck for short in all the harness
and components connected to the
DOME fuse (See attached wiring
diagram).1
Check and repair harness and connector
between ECU and battery. Proceed to next circuit inspection
shown on matrix chart (See page
BE±371
).
Repair or replace harness or
connector.
Check voltage between terminals +B1
and E of ECU connector.
Check for open in harness and connector
between ECU and body ground (See page
IN±27 ).
OK
OK
NG
NG
2
3
WIRING DIAGRAM
CIRCUIT INSPECTION
ECU Power Source Circuit
CIRCUIT DESCRIPTION
This circuit provides power to operate the theft deterrent and door lock ECU\
.
DIAGNOSTIC CHART
BE±376±
BODY ELECTRICAL SYSTEM Door Lock Control System
WhereEverybodyKnowsYourName

OKNG
NGOK
OKNG
INSPECTION PROCEDURE
1Check 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 the DOME fuse (See attached wiring diagram).
2Check voltage between terminals +B1 and E of ECU connector.
C
OK
P1. Remove the No. 1 under cover and heater duct.
2. Disconnect the theft deterrent and door lock ECUconnectors.
Measure voltage between terminals +B1 and E of ECU
connector.
Voltage: 10 ± 14 V
Proceed to next circuit inspection shown on matrix chart
(See page BE±371).
3Check for open in harness and connector between ECU and body ground (Se\
e page IN±27).
Repair or replace harness or connector.
Check and repair harness and connector between
ECU and battery.
±
BODY ELECTRICAL SYSTEM Door Lock Control SystemBE±377
WhereEverybodyKnowsYourName

NGOK
NG
OK
1
2
Check P/W fuse.
Check voltage between terminal +B2 of
ECU connector and body ground.
Check and repair harness and connectors
between ECU and battery
(See page IN±27). Check for short in all the harness
and components connected to the
DOOR fuse (See attached wiring
diagram).
*1
Proceed to next circuit inspection
shown on matrix chart (See page
BE±371
).
WIRING DIAGRAM
*1: The power source is supplied to the actuator
(door lock motor, luggage compartment door
opener motor) through the theft deterrent and
door lock ECU. Accordingly, if a short circuit of
the W/H or actuator occurs in the actuator circuit,
the DOOR fuse may become OPEN. so also in-
spect the actuator (door lock motor circuit on
page BE±380 , and the luggage compartment
door opener motor circuit on page BE±382).
Actuator Power Source Circuit
CIRCUIT DESCRIPTION
This circuit provides power to drive the door lock motor and the luggage com\
partment door opener mo-
tor.
DIAGNOSTIC CHART
BE±378±
BODY ELECTRICAL SYSTEM Door Lock Control System
WhereEverybodyKnowsYourName