ignition switch LEXUS SC400 1991 Service Repair Manual

31NoiseNOISE PRODUCED WHEN ENGINE STARTS
Whistling noise which becomes high±pitched when
accelerator strongly depressed, disappears shortly
after engine stops.Whining noise occurs when A/C is operating.
Scratching noise occurs during sudden accel-
eration, driving on rough roads or when ignition
switch is turned on.
Clicking sound heard when horn button is
pressed, then released. Whirring/grating sound
when pushed continuously.
Murmuring sound, stops when engine stops. Tick±tock noise, occurs in coordination with
blinking of flasher.
Noise occurs during window washer operation.Scratching noise occurs while engine is running,
continues a while even after engine stops.Scraping noise in time with wiper beat.
Other type of noise. Alternator noise.
A/C noise.
Fuel gauge noise.
Horn noise.
Ignition noise. Turn signal flasher noise.
Washer noise. Water temp. gauge noise.
Wiper noise.
±
BODY ELECTRICAL SYSTEM AUDIO SYSTEMBE±259
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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.
\b PROBLEM SYMPTOM CONFIRMATION,  SYMPTOM SIMULATION.
Confirm the problem symptoms. If the problem does not reappear, be sure to simulate the problem using
the ºProblem Simulation Methodsº.
When checking the problem symptoms, pay attention to the following points to\
accurately define the symp-
toms and the extent of the problem:
For ºNot Functioningº problems:
(1) Is the problem only in one part (e.g. ºreclining onlyº), or ever\
ything?
(2) Is the problem only for manual operation, only for position return opera\
tion, or for both manual and position return operation?
(3) Is tilt, telescopic and outer mirror operation normal?
(4) Does the problem occur with the ignition key inserted, or not inserted?
 MATRIX CHART OF PROBLEM SYMPTOMS
Confirm the order of inspection on the matrix chart for the particular problem symptom involved. For ºNot
Functioningº problems, pay attention to the points in \b. to find out the specifics of the problem, then choose
the most appropriate problem symptom from among those listed on the matr\
ix chart, and proceed with trou-
bleshooting accordingly.
 CIRCUIT INSPECTION
Proceed with diagnosis of each circuit in accordance with the inspection\
order confirmed in .
Determine whether the cause of the problem is in the sensor, actuators, wire harness and connectors, or
the ECU.
 POSITION SENSOR CHECK
This function checks that the signal from each position sensor is correctly input into\
the ECU when the
manual switch is turned ON. The instructions for this diagnosis are included in\
the flow chart for the position
sensor circuit.
 REPAIR
After the cause of the problem is located, perform repairs by following the i\
nspection and replacement pro-
cedures is this manual.
 CONFIRMATION TEST
After completing repairs, confirm that the problem is eliminated and that tilt, telescopic and outer mirror
operation is normal.
BE±268
±
BODY ELECTRICAL SYSTEM Power Seat Control System (Driver's Seat)
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WIRING DIAGRAM
No.SymbolTerminal NameNo.SymbolTerminal NameNo.SymbolTerminal Name
P11
±1SLDFSlide Switch (Forward)P11±13CHKCheckP10±7IGIgnition Switch
2RCLFReclining Switch (Forward)14SSRRReclining Sensor8GND2Ground 2
3FUPFront Vertical Switch (UP)15SSRVRear Vertical Sensor9SLD±Slide Motor (Back)
4RUPRear Vertical Switch (UP)16SSRSSlide Sensor10RCL±Reclining Motor (Down)
5SSFVFront Vertical Switch17SOSerial Communications11FRV±Front Vertical Motor (Down)
6PVCCPosition Sensor Power
Source18SGNDSensor Ground12RRV±Rear Vertical Motor (Down)
7SYSBPower SourceP10±1GNDGround13RRV+Rear Vertical Motor (For-
ward)
8SISerial Communications2SLD+Slide Motor (Forward)14+B2Power Source
9SLDRSlide Switch (Back)3RCL+Reclining Motor (Up)15PNeutral Start Switch
10RCLRReclining Switch (Back)4FRV+Front Vertical Motor (Up)16±±±±
11FDWNFront Vertical Switch (Down)5+BPower Source
12RDWNRear Vertical Switch (Down)6STOPStop Light
BE±272±
BODY ELECTRICAL SYSTEM Power Seat Control System (Driver's Seat)
WhereEverybodyKnowsYourName

OKNG
NGOK
INSPECTION PROCEDURE
1Check the shift position indicator.
Check that P lights up on the shift indicator when P range is shifted in\
to, and that P is OFF when
shiftin
g into another range.
C
Check shift position indicator circuit (See page BE±141).
2Check voltage between terminal P of ECU connector and body ground.
C
OK
PRemove ECU with connectors still connected.
(1) Turn ignition switch ON.
(2) Measure voltage between terminal P of ECU con-nector and body ground when the shift lever is posi-
tioned to the following ranges.
Shift range
P
1
0
Other than PVoltage
10 ± 14 V
Below 1 V
Proceed to next circuit inspection shown on matrix chart
(See page BE±276).
Check and repair harness and connector between
ECU and connector.
±
BODY ELECTRICAL SYSTEM Power Seat Control System (Driver's Seat)BE±301
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WIRING DIAGRAM
Ignition Switch Circuit
CIRCUIT DESCRIPTION
This circuit sends an ignition switch ON or OFF signal to the ECU.
DIAGNOSTIC CHARTDIAGNOSTIC CHART
Check ECU±IG fuse.NG
Check for short in all the harness
and components connected to
ECU±IG fuse.
Check voltage between terminal IG of
ECU connector and body ground. OK
OK
NG Proceed to next circuit inspection
shown on matrix chart
(See page
BE±276).
Check and repair harness or connector
between ECU and battery (See page IN±27).
BE±302±
BODY ELECTRICAL SYSTEM Power Seat Control System (Driver's Seat)
WhereEverybodyKnowsYourName

OKNG
NGOK
INSPECTION PROCEDURE
1Check ECU ± IG fuse.
Check for short in all the harness and components con-
nected to ECU±IG fuse.
2Check voltage between terminal IF of ECU connector and body ground.
C
PRemove ECU with connectors still connected.
Measure voltage between terminal IG of ECU connector
and body ground when ignition switch is on and off.
Ignition switch Voltage
ON
OFF 10 ± 14 V
Below 1 V
Proceed to next circuit inspection shown on matrix chart
(See page BE±276).
Check and repair harness or connector between
ECU and battery (See page IN±27).
±
BODY ELECTRICAL SYSTEM Power Seat Control System (Driver's Seat)BE±303
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STANDARD VALUE OF ECU TERMINAL
 

Terminals 

Symbols 


Wiring
Color 

Condition 

Standard Value
 P12±1
eP12±16 SYS eBGND Re W±B Always 10 ~ 14 V
 

P12±2
e
 

SLSW
e
 

V±W
e
 


Slide neutral limit switch OFF
(Passenger's seat is slided at most back position, when
power seat operation) 

10 ~ 14 V
 




P12 2
e
Body Ground 




SLSW
e
Body Ground 




VW
e
Body Ground 




Slide neutral limit switch ON
(Passenger's seat is slided 120 mm or more from most
back position, when power seat operation) 




Below 1 V
P12±3
eP12±15PVCC eSGNDVe BRAlways (When power seat operation)10 ~ 14 V P12±4 DOUT ' ' ' 
P12 eP12 16
 
SLDR eGND
 
LR eWB
 Slide switch is pushed back 10 ~ 14 V P12 eP12±16 SLDR eGND L±R eW±B Others Below 1 V
 
P12 6 eP12 16
 
SLDF eGND
 
LY eWB
 Slide switch is pushed forward 10 ~ 14 V
 P12±6 eP12±16 SLDF eGND L±Y eW±B Others Below 1 V
 P12 7 eP12 16 SLD+ eGND Le WB Slide switch is pushed forward 10 V ~ 14 V
 P12±7 eP12±16 SLD+ eGND Le W±B Others Below 1 V
P12±8 eP12±16+B eGNDL±W eW±BAlways10 ~ 14 V 

P12±9
e
 

PRDC
e
 

B
e
 

Passenger's buckle switch ON and ignition switch ON
(Tung plate is inserted into buckle switch) 

Below 1 V
 


P12 9
e
Body Ground 


PRDC
e
Body Ground 


B
e
Body Ground 


Passenger's buckle switch OFF and Ignition switch ON
(Tung plate is not inserted into buckle switch) 

10 ~ 14 V
 

P12±10
e
 

RFSW
e
 

Y
e
 


Reclining front limit switch OFF (Passenger's seat
back is moved backward, when power seat operation) 

10 ~ 14 V
 
P12 10
e
Body Ground 
RFSWe
Body Ground 
Ye
Body Ground Reclining front limit switch ON (Passenger's seat
back is moved forward, when power seat operation) Below 1 V
 

P12±11
eP12±15
 

SSRS
eSGND
 

LG
eBR
 


When passenger's seat is sliding back and forth,
when power seat operation 

0
e 12 V
 

P12±12
e
 

PBCL
e
 

B±Y
e
 


Passenger's buckle switch OFF (Tung plate is not
inserted into buckle switch, when power seat operation) 

10 ~ 14 V
 
P12 12
e
Body Ground 
PBCLe
Body Ground 
BYe
Body Ground Passenger's buckle switch ON (Tung plate is inserted
into buckle switch, when power seat operation) Below 1 V
 


P12 13
eP12 16
 


PRSW
eGND
 


LG R
eWB
 

Reclining rear limit switch OFF (Passenger's seat
back is moved backward, when power seat operation) 

10 ~ 14 V
 


P12±13
eP12±16 


PRSW
eGND 


LG±R
eW±B 


Reclining rear limit switch ON (Passenger's seat
back is moved forward, when power seat operation) 

Below 1 V
 P12±14 CHK ' ' '
P12±15
eSGNDeBReAlways1
or less Body Ground Body Ground Body Ground Always 1
or less
 P12±16 e GNDe W±Be 
Always
 
1
or less Body Ground Body Ground Body Ground Always 1
or less
 
P12 17 eP12 16
 
SLD eGND
 
LB eWB
 Slide switch is pushed back 10 ~ 14 V
 P12±17 eP12±16 SLD± eGND L±B eW±B Others Below 1 V
 P12±18 ' ' ' '
BE±318±
BODY ELECTRICAL SYSTEM Power Seat Control System (Passenger's Seat)
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
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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
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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