ECU LEXUS SC400 1991 Service Manual PDF

Troubleshooting
You will find the cause of trouble more easily by properly using the table \
shown below. In this table, the
numbers indicate the order of priority of the causes of trouble. Check each part in \
the order shown. If neces-
sary, replace the part.
See pageBE±4 ,20BE±4,21BE±186BE±186 ±±BE±188SR±60 ±±IN±32BE±187
TroubleParts
name
RADIO NO. 2 FuseDOME FuseMirror SwitchMirror MotorWire HarnessMirror ECUDriving Position SwitchDriving Position Switch
(Position is not set)Tilt and Telescopic ECUMirror Sensors
Mirror does not operate.112354
Mirror operates abnormally1243
Mirror does not return to the memorized position.
(w/ Memory System)642135
Mirror returns to a position which is not memorized.
(w/ Memory System)312
BE±190±
BODY ELECTRICAL SYSTEM Power Mirror Control System
WhereEverybodyKnowsYourName

TROUBLESHOOTING
NOTICE: When replacing the internal mechanism (ECU part) of the audio system,\
be careful that no part
of your body or clothing comes in contact with the terminals of the lead\
s from the IC, etc. of the replace-
ment part (spare part).
HINT:
This inspection procedure is simple troubleshooting which should be carried \
out on the vehicle during
system operation and is based on the assumption that the cause of trouble lies\
with the system
components (excluding the wires and connectors, etc.).
Always inspect the trouble taking the following items into consideration\
.
Open or short circuit of the wire harness

Connector or terminal connection fault

The cassette tape or compact disc itself may be causing the trouble, so whe\
n troubleshooting the tape
player or CD player, always use a different cassette tape or compact disc first of all to check operation
of the tape player or CD player.

For some of problems in the following problem chart, the AUDIO SYSTEM CHECKER can be used
to inspect malfunctions of the Radio or Tape Player, and the CD PLAYER CHECKER can be used to
inspect the CD player.
The portions indicated by on the flow charts on the following pages can be\
inspected using a CHECK-
ER.
For instructions on how to connect the checker to the vehicle and how to\
use the checker, please refer
to the instruction Manual for AUDIO SYSTEM CHECKER or CD PLAYER CHECKER.
BE±218
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BODY ELECTRICAL SYSTEM AUDIO SYSTEM
WhereEverybodyKnowsYourName

32AntennaANTENNA±RELATED
Does antenna extend when radio switched ON?Wire harness faulty.
Is there battery voltage between the following
terminals with connector disconnected?


Motor antenna control relay 6 ± ground

Motor antenna control relay 14 ± ground

Motor antenna control relay 3 ± ground
Wire harness faulty.Replace fuses.
Radio receiver assembly faulty.
Check if ECU±IG, RADIO No. 1 and RADIO No.
2 fuse are OK.
ªAMº button turned ON.
Is there battery voltage between the following
terminals with connector connected?

Radio receiver assembly A9 (*A1) ± ground

Radio receiver assembly A8 ± ground

Radio receiver assembly D4 ± ground

Radio receiver assembly D10 ± ground Radio receiver side
faulty.
Motor antenna faulty.
Temporarily install another motor antenna is
radio operating normally?
Glass printed antenna faulty.
Check if glass printed antenna is OK.
Is there continuity between the following terminals
with connector disconnected?

Motor antenna control relay 4 ± ground
Continued on next page.
BE±260±
BODY ELECTRICAL SYSTEM AUDIO SYSTEM
WhereEverybodyKnowsYourName

DESCRIPTION
The Power Seat Control System carries out seat slide, front vertical, rear \
vertical, reclining and lumbar support
position adjustments electrically. Power seat switch and lumbar support switch.
In addition, operation of the memory switch makes it possible to store the positions of the slide, front vertical,
rear vertical and reclining adjustments in memory and return to the posi\
tion.
The component parts of this system and their function are described in t\
he following table.
 Parts Name\
 \
Function
 








Driver's Seat ECU
\
 
\


\


\


\

\

The seat ECU controls power operation, memory operation, and position re\
turn
operation of the power seat. When input is received from the power seat \
switch,
the relay inside the ECU is controlled and the power seat operates. The \
seat
memory and position return are controlled by mutual communication betwee\
n the
electrically operated Tilt and Telescopic ECU and the seat ECU.
 

Power Seat Switch\
 
\

\

Operation of this switch sends slide, front vertical, rear vertical, rec\
lining signals
to ECU.
 




Driving Position
Memory and Return
Switch\
 
\


\

\

Memory and Return Signals are sent to the seat ECU via the Tilt and Telescopic
ECU.
 






Lumbar Support
Switch
\
 
\


\


\

\

This switch is supplied with power from the DOOR fuse. When the switch i\
s
operated, power is supplied to the lumbar support motor controlling the \
direction
in which the motor turns and turning the current ON and OFF. This switch is not
connected to the ECU and the adjustment position cannot be stored in mem\
ory
for return operation.
 

Position Sensor
\
 
\

\
This sensor sends signals on the position of each motor (slide, front v\
ertical, rear
vertical and reclining) to the ECU for use in memory and return.
 

*Motor
\
 
\

\

These motors operate on current from the driver's seat ECU moving the various
parts of the seat directly. Each motor has a built±in circuit breaker.
*: Slide, Front Vertical, Rear Vertical, Lumbar Support and Reclining.
Motors contained in each seat are described in the following table.
 Motor Slide Front
Vertical
 Rear
Vertical
 Reclining Lumbar
Support 

Seat 

Motor 


Vertical
Motor
 


Vertical
Motor
 


g
Motor 


Support
Motor
 Driver's Seat O* O* O* O* O
*: Operated by the memory and return functions. BE±266
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BODY ELECTRICAL SYSTEM Power Seat Control System (Driver's Seat)
WhereEverybodyKnowsYourName

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
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BODY ELECTRICAL SYSTEM Power Seat Control System (Driver's Seat)
WhereEverybodyKnowsYourName

STANDARD VALUE OF ECU TERMINAL
TerminalsSymbolsWiringColorConditionStandard Value
P11±1 eBody
GroundSLDF eBody
Ground
LSeat moved forward using slide SWBelow 1 VL
Others10±14 V
P11±2 eBody
GroundRCLF eBody
GroundY±RSeat moved forward using reclining SWBelow 1 V
Others10±14 V
P11±3 eBody
GroundFUP eBody
GroundL±YSeat raised using front vertical SWBelow 1 V
Others10±14 V
P11±4 eBody
GroundRUP eBody
GroundY±GSeat raised using rear vertical SWBelow 1 V
Others10±14 V
P11±5 eP11±18SSFV eSGNDLG±R eBR±BFront vertical operation0 V e8 V
P11±6 eP11±18PVCC eSGNDVe BR±BManual position return operation8 V
P11±7 eP10±1SYSB eGNDRe W±BAlways10±14 V
P11 8SIW
Signals between power seat ECU & tilt
telescopic ECU0 V e12 V
P11±8SIW
OthersResistance
(approx. 2.5 k
)
P11±9 eBody
GroundSLDR eBody
Ground
L±BSeat moved to rear using slide SWBelow 1 VL±B
Others10±14 V
P11±10 eBody
GroundRCLR eBody
Ground
Y±BSeat moved to rear using reclining SWBelow 1 VY±B
Others10±14 V
P11±11 eBody
GroundFDWN eBody
Ground
L±RSeat lowered using front vertical SWBelow 1 VL±R
Others10±14 V
P11±12 eBody
GroundRDWN eBody
Ground
Y±LSeat lowered using rear vertical SWBelow 1 VY±L
Others10±14 V
P11±13CHK
P11±14 eP11±18SSRR eSGNDV±W eBR±BReclining operation0 V e8 V
P11±15 eP11±18SSRV eSGNDY±G eBR±BRear vertical operation0 V e8 V
P11±16 eP11±18SSRS eSGNDLG eBR±BSlide operation0 V e8 V
±
BODY ELECTRICAL SYSTEM Power Seat Control System (Driver's Seat)BE±273
WhereEverybodyKnowsYourName

 
P11±17 SO B Signals between power seat ECU & tilt 0Ve12 V   B 
Signals between ower seat ECU & tilt
telescopic ECU 0 V e12 V
 P11±18 SGND BR±B Always Below 1 V
 P10±1 GND W±B Always Below 1 V
 P10±2 eP10±1 SLD+ eGND Le W±B Seat moved forward using slide SW 10±14 V
    Others Below 1 V
 

P10±3
eP10±1
 

RCL+
eGND
 

Y±R
eW±B
 


Seat moved forward using reclining
SW 

10±14 V
    Others Below 1 V
 P10±4
eP10±1 FRV+ eGND L±Y eW±B Seat raised using front vertical SW 10±14 V
    Others Below 1 V
 P10±5 +B L±W Always 10±14 V P10±6 eBody Ground STOP eBody Ground Ge W Brake pedal depressed 10±14 V    Others (Several
or less) Below 1 V P10±7 IG B±R Ignition SW ON 10±14 V P10±8 GND2 W±B Always Below 1 V P10±9 eP10±1 SLD± eGND L±B eW±B Seat moved to rear using slide SW 10±14 V    Others Below 1 V 
P10±10 eP10±1
 
RCL± eGND
 
Y±B eW±B
 
Seat moved to rear using reclining SW
 
10±14 V    
Others
 
Below 1 V 

P10±11
eP10±1
 

FRV±
eGND
 

L±R
eW±B
 

Seat lowered using front vertical SW
 

10±14 V
    Others Below 1 V
 P10±12
eP10±1 RRV± eGND Y±LW±B Seat lowered using rear vertical 10±14 V
    Others Below 1 V
 P10±13 eP10±1 RRV+ eGND Y±L eW±B Seat raised using rear vertical 10±14 V
    Others Below 1 V
 P10±14 +B2 L±W Always 10±14 V
 P10±15 eBody Ground Pe Body Ground GR Shift lever in ºPº with IG ON 10±14 V
    Others (10
or less) Below 1 V
 P10±16 ±± ±± ±± ±±
BE±274±
BODY ELECTRICAL SYSTEM Power Seat Control System (Driver's Seat)
WhereEverybodyKnowsYourName

See page
BE±284
BE±28 6
BE±28 8
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.
The Driver's Seat ECU communicates with the tilt & telescopic ECU about memory and \
return, so there are occa-
sions when a power seat problem symptom is caused by trouble in the tilt and telescopic circuit.\
When the
instruction ºSee tilt and telescopic sectionº appears in the matrix chart, pr\
oceed to the matrix chart (see page
SR±28 ) in the tilt and telescopic section and inspect the circuits as direct\
ed by the matrix chart.
BE±276
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BODY ELECTRICAL SYSTEM Power Seat Control System (Driver's Seat)
WhereEverybodyKnowsYourName

BE±292
BE±29 4
BE±29 8
BE±30 0
BE±30 2
BE±30 4
BE±30 6
IN±32
See tilt and telescopic section on page SR±28
See tilt and telescopic section on page SR±28
See tilt and telescopic section on page SR±28
HINT:
w
If the instruction ºProceed 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.
w If the trouble still reappears even though there are no abnormalities in a\
ny of the other circuits, then check
and replace the driver's seat ECU as the last step.
±
BODY ELECTRICAL SYSTEM Power Seat Control System (Driver's Seat)BE±277
WhereEverybodyKnowsYourName

CIRCUIT INSPECTION
+B Power Source Circuit
CIRCUIT DESCRIPTION
This is the power source for motors such as the slide motor and reclining mo\
tor.
DIAGNOSTIC CHARTDIAGNOSTIC CHART
Check Door fuse.NG
Check for short in all harness and
components connected to the
DOOR fuse (See attached wiring
diagram).
Check voltage between terminals +B, +B2
and GND of ECU connector. OK
OKProceed to next circuit inspection
shown on matrix chart (See page
BE±276
).
Check continuity between terminal GND
of ECU connector and body ground. NG
NGRepair or replace harness or
connector.
OK
Check and repair harness or connector
between ECU and battery.
WIRING DIAGRAM
BE±284±
BODY ELECTRICAL SYSTEM Power Seat Control System (Driver's Seat)
WhereEverybodyKnowsYourName