1991 LEXUS SC400 ignition

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

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
WhereEverybodyKnowsYourName

NGOK
OKNG
OKNG
*1: malfunction of the ECU can be considered possibleonly when the problem symptom is the following:

Lock and/or unlock using the Door Lock Con-
trol Switch cannot be done, neither on the driv-
er's side nor on the passenger's side.
INSPECTION PROCEDURE
1Check voltage between terminals 2(3), 1(1) of door lock control switch co\
nnector and body
ground.
C
OK
Hint
PRemove the door trim and service hole cover.
1. Turn ignition switch ON.
2. Measure voltage between terminals 2(3), 1(1) of door lock control switch connector and body
ground, when door lock control switch is pressed to
the lock side, unlock side and not pressed.
The terminal number without brackets is for the LH, the
number with brackets is for the RH.
Proceed to next circuit inspection shown on matrix chart
(See page BE±371).
2Check door lock control switch.
C
OK
Hint
PDisconnect the door lock control switch connector.
Check continuity between terminals 2(3), 1(1), and 8(2)
of door lock control switch connector, when door lock
control switch is pressed to the lock side, and unlock
side and not pressed.
The terminal number without brackets is for the LH, the
number with brackets is for the RH.
Replace door lock control switch.
3Check harness and connectors between ECU and door lock control switch, s\
witch and body
ground (See page IN±27).
Repair or replace harness or connector.
Check and replace ECU. *1
±
BODY ELECTRICAL SYSTEM Door Lock Control SystemBE±385
WhereEverybodyKnowsYourName

OKOK NG NG
Check key unlock warning switch.
Check harness and connectors between ECU and
key unlock warning switch, key unlock warning
switch and body ground (See page
IN±27).
Replace key unlock warning
switch.1
2
Proceed to next circuit inspection shown on
matrix chart (See page BE±371). Repair or replace harness or
connector.
WIRING DIAGRAM
Key Unlock Warning Switch Circuit
CIRCUIT DESCRIPTION
The key unlock warning switch goes on when the ignition key is inserted in the key cylinder and goes
off when the ignition key is removed.
The ECU operates the key confinement prevention function while the key unlo\
ck warning switch is on.
DIAGNOSTIC CHARTDIAGNOSTIC CHART
BE±388±
BODY ELECTRICAL SYSTEM Door Lock Control System
WhereEverybodyKnowsYourName

DESCRIPTION
The wireless door lock control system is to lock and unlock all the doors a\
t a distance, transmitting a weak radio
wave from a transmitter contained in the master ignition key.
The weak radio wave (coded differently for each key) is sent to the receiver via the rear window defo\
gger wiring.
For the function of the component parts of this system, refer to the circui\
t description in circuit inspection.
PARTS LOCATION
BE±440±
BODY ELECTRICAL SYSTEM Wireless Door Lock Control System
WhereEverybodyKnowsYourName

DESCRIPTION
The wireless door lock control system is to lock and unlock all the door\
s at a distance, transmitting a weak radio
wave from a transmitter contained in the master ignition key.
The weak radio wave (coded differently for each key) is sent to the receiver via the rear window defo\
gger wiring.
For the function of the component parts of this system, refer to the circui\
t description in circuit inspection.
PARTS LOCATION
BE±440±
BODY ELECTRICAL SYSTEM Wireless Door Lock Control System
WhereEverybodyKnowsYourName

STANDARD VALUE OF ECU TERMINAL
 

Terminals
 

Symbols
 

Wiring
color 

Condition
 

Standard
Value
 

W8±1
eW8±7
 

+B1
eE
 

R±L
eW±B
 

Wireless door lock main switch ON 

10 ~ 14 V 


W8±1eW8±7 


+B1eE 


R±LeW±B 

Wireless door lock main switch OFF
 

Below 1 V
 W8±2
eBody LSWD1 eBody L±W eBody Door lock knob of driver's door LOCK 8 ~ 10 V
 
y
Ground 
y
Ground 
y
Ground Door lock knob of driver's door UNLOCK Below 1 V
 W8±3 eBody LSWP eBody P±B eBody Door lock knob of assistant's door LOCK 8 ~ 10 V
 
y
Ground 
y
Ground 
y
Ground Door lock knob of assistant's door UNLOCK Below 1 V
 


W8 4
eBody
 


UL1
eBody
 


GW
eBody
 


Turn ignition switch ON,
Key operate switch Left and Right UNLOCK 


Below 1 V 


W8±4
eBody
Ground 


UL1
eBody
Ground 


G±W
eBody
Ground 


Turn ignition switch ON
Key operate switch Left or Right UNLOCK 


Below 1 V
    Except above mention 8 ~ 10 V
 

W8±5
eBody
 

L1
eBody
 

G±Y
eBody
 

Turn ignition switch, ON
Key operate switch Right LOCK 

Below 1 V
 


y
Ground 


y
Ground 


y
Ground 

Turn ignition switch ON,
Except above mention 

8 ~ 10 V
 W8±6
eBody KSW eBody Ye Body Ignition key insert key cylinder Below 1 V 

y
Ground 

y
Ground 

y
Ground 
Ignition key pull out key cylinder 
10 ~ 14 V 

W8±7
eBody
Ground
 

E
e Body
Ground
 

W±B
eBody
Ground
 

Always
 

Below 1 V
 

W8±9
eBody
 

LSWD2
eBody
 

W±L
eBody
 

Door lock knob of driver's door LOCK
 

8 ~ 10 V
 
y
Ground 
y
Ground 
y
Ground Door lock knob of driver's door UNLOCK Below 1 V
    Door open detection switch Left and Right ON 
 W8±10
eBody DSWD eBody G±L eBody Door open detection switch Left or Right ON Below 1 V
 
y
Ground 
y
Ground 
y
Ground Door open detection switch Left or Right OFF 
    Door open detection switch Left and Right OFF 10 ~ 14 V
±
BODY ELECTRICAL SYSTEM Wireless Door Lock Control SystemBE±453
WhereEverybodyKnowsYourName

NGOK
INSPECTION PROCEDURE
1Check voltage between terminals LSWD1, LSWP and LSWD2 of ECU connector a\
nd body
ground.
C
OK
P1. Remove the rear seat and RH quarter trim panel.
2. Remove the ECU.
3. Turn ignition switch on.
Measure voltage between terminals LSWD1, LSWP
and LSWD2 of ECU connector and body ground, when
the respective door lock knob involved is pushed to the
lock side.
Voltage: 8 ± 10 V
Proceed to next circuit inspection shown on matrix chart
(See page BE±454).
Check and repair harness and connector between ECU and door unlock detec\
tion switch.
±
BODY ELECTRICAL SYSTEM Wireless Door Lock Control SystemBE±463
WhereEverybodyKnowsYourName