fuse chart LEXUS SC400 1991 Service Service Manual

DIAGNOSTIC CHART
DIAGNOSTIC
CHART
Check for short in all the harness and
components connected to IGN fuse.
Check voltage of terminal M±REL.
Check for open in harness and connector
between battery and ECU.
Check and replace ECU.
Replace ignition switch.
Repair or replace harness or
connector.
Repair or replace harness or
connector.
Check for open and short in harness and
connector between terminal M REL and body
ground.
Replace EFT main relay.
Check voltage of terminal IGSW.
Check IGN fuse.
Check continuity between terminals E1 and
body ground.
Check voltage of ECU power source.
Proceed to next circuit inspection
shown on matrix chart (See page
TR±35
).
Check ignition switch.
Check EFT fuse.
Check EFT main relay.
Check and repair or harness or connector
between EFI fuse and battery.
Check for short in all the harness and
components connected to EFI fuse.
±
ENGINE TROUBLESHOOTING Circuit InspectionTR±125
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Check EFI fuse.
Check voltage of terminal BATT.
Check operation for the back±up.
Proceed to next circuit inspection
shown on matrix chart (See page TR±39).
Check for short in all the harness and
components connected to EFI fuse.
Check and repair harness or connector
between battery, EFI fuse and ECU.
Check and replace fuse.
WIRING DIAGRAM
Back Up Power Source Circuit
CIRCUIT DESCRIPTION
Battery voltage is supplied to terminal BATT of the ECU even when the ignition switch is off for use
by the diagnostic code memory and air±fuel ratio adaptive control val\
ue memory, etc.
DIAGNOSTIC CHART
TR±126±
ENGINE TROUBLESHOOTING Circuit Inspection
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OKNG
OKNG
YESNO
INSPECTION PROCEDURE
1Check EFI fuse.
C
OK
PRemove EFI fuse from R/B No. 2
Check continuity of EFI fuse.
Continuity
Check for short in all the harness and components
connected to EFI fuse (See attached wiring diagram).
2Check voltage between terminal BATT of engine (& ECT) ECU connector and body ground.
C
OK
PConnect the Check Harness A. (See page TR±34)
Measure voltage between terminal BATT of engine
(& ECT) ECU connector and body ground.
Voltage: 10 ± 14 V
Check and repair harness or connector between engine
(& ECT) ECU and EFI fuse, EFI fuse and battery.
3Are the diagnostic trouble codes still in the memory when the ignition s\
witch is turned OFF?
Check and replace engine (& ECT) ECU.
Proceed to next circuit inspection shown on
matrix chart (See page TR±39).
±
ENGINE TROUBLESHOOTING Circuit InspectionTR±127
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Injector Circuit
CIRCUIT DESCRIPTION
The injectors are provided to the intake manifold. They inject fuel into th\
e cylinders based on the
signals from the engine (& ECT) ECU.
Reference INSPECTION USING OSCILLOSCOPE
w With the engine idling measure between terminals #10 ~ 60 and E01 of engine (& ECT) ECU.
HINT: The correct waveform appears as shown in the illustration on the below\
.
DIAGNOSTIC CHART
Check voltage of terminals #10 ~ 60.
Check AM2 and INJ fuses.
Check for open in harness and connector
between ECU and battery.
Check continuity between terminals E01,
E02 and body ground.
Check operation for injectors.
Check and replace ECU. Check for short in all the harness
and components connected to
AM2 and INJ fuses.
Repair or replace harness or
connector.
Replace injector.
TR±128±
ENGINE TROUBLESHOOTING Circuit Inspection
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Back Up Power Source Circuit
CIRCUIT DESCRIPTION
Battery voltage is supplied to terminal BATT of the ECU even when the ignition switch is off for use by
the diagnostic code memory and air±fuel ratio adaptive control value mem\
ory, etc.
DIAGNOSTIC CHARTDIAGNOSTIC CHART
Check for short in all the harness and
components connected to EFI fuse.Check EFI fuse.
Check of terminal BATT.
Proceed to next circuit inspection shown on
matrix chart (See page TR±35).
Check operation for the back up.Check and replace ECU.
Check and repair harness or connector
between battery, EFI fuse and ECU.
WIRING DIAGRAM
TR±130±
ENGINE TROUBLESHOOTING Circuit Inspection
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OKNG
OKNG
YESNO
INSPECTION PROCEDURE
1Check EFI fuse.
C
OK
PRemove EFI fuse from R/B No.2.
Check continuity of EFI fuse.
Continuity
Check for short in all the harness and components con-
nected to EFI fuse (See attached wiring diagram).
2Check voltage between terminal BATT of engine & ECT ECU connector and body ground.
C
OK
PConnect the Check Harness A.
(See page TR±30).
Measure voltage between terminal BATT of engine &
ECT ECU connector and body ground.
Voltage: 10 ± 14 V
Check and repair harness or connector between engine
& ECT ECU and EFI fuse, EFI fuse and battery.
3Are the diagnostic codes still in the memory when the ignition switch is\
turned OFF?
Check and replace engine & ECT ECU.
Proceed to next circuit inspection shown on ma-
trix chart (See page TR±35).
±
ENGINE TROUBLESHOOTING Circuit InspectionTR±131
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Check voltage of ECU power source.
Check continuity between terminals E1 and
body ground.
Check voltage of terminal IGSW.
Check IGN fuse.
Check ignition switch.
Check for open in harness and connector
between battery and ECU.
Check voltage of terminal M±REL.
Check EFI fuse.
Check EFI main relay.Check for open and short in harness and
connector between terminal M±REL and
body ground.
Check and repair harness or connector
between EFI fuse and battery.
Repair or replace harness or
connector.
Replace EFI main relay.
Check for short in all the harness
and components connected to the
EFI fuse.
Check and replace ECU.
Replace ignition switch.
Check for short in all the harness and
components connected to IGN fuse.
Repair or replace harness or
connector.
Proceed to next circuit inspection
shown on matrix cart (See page
TR±39
).
DIAGNOSTIC CHART
±
ENGINE TROUBLESHOOTING Circuit InspectionTR±121
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* The system shown here is an EXAMPLE ONLY. It is different to the actual circuit shown in the SYSTEM CIRCUITS SECTION.
POWER SOURCE (Current Flow Chart)
The chart below shows the route by which current flows from the battery to \
each electrical source (Fusible Link, Circuit
Breaker, Fuse, etc.) and other parts.
The next page and following pages show the parts to which each electrica\
l source outputs current.
POWER SOURCE
8
HOW TO USE THIS MANUAL
The ªCurrent Flow Chartº section, describes which parts each power so\
urce (fuses, fusible links, and circuit breakers)
transmits current to. In the Power Source circuit diagram, the conditions when ba\
ttery power is supplied to each system are
explained. Since all System Circuit diagrams start from the power source, the power\
source system must be fully understood.
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44
POWER SOURCE (Current Flow Chart)
The chart below shows the route by which current flows from the battery to \
each electrical source
(Fusible Link, Circuit Breaker, Fuse, etc.) and other parts.
The next page and following pages show the parts to which each electrica\
l source outputs current.
Taillight
Relay (Point Side)
30A AM260A MAIN 50A DEFOG
60A HEATER
7.5 TRAC
40A IG SW
120A ALT
Starter Relay
(Point Side)
Headlight Relay
(Point Side)
30A EFI
15A TEL
10A DOME
20A RADIO No. 1
25A HAZ±HORN
Theft Deterrent and
Door Lock ECU
15A HEAD RH
(USA) 15A HEAD LH
(USA)
Dimmer Relay
(Coil Side)
Starter
15A STOPIgnition SW
(AM1)
30A DOOR
15A TAIL
Alternator
ABS Motor Relay
(Point Side)
Defogger
Relay
Starter ABS
Actuator
10A MIR±HTR
15A ECU±B 7.5A PANEL
7.5 IGN
Engine ECU Traction Brake
Actuator
30A INJ
60A ABS No.1
Traction Brake
Main Relay
(Point Side)
ABS
Actuator Relay
30A POWER
Integration
Relay
100A AM1
Seat Heater
Relay (Point Side)
7.5 ALT SENCING
30A ABS No.2 Headlight
Relay
(Coil Side)
Traction Motor
Relay (Point Side)Traction Pump
and Motor Dimmer Relay
(Point Side) Ignition SW
(AM2)
Taillight
Relay (Coil Side)
15A HEAD (LH±LWR)
(CANADA)
15A HEAD (RH±LWR)
(CANADA)
Engine and
ECT ECU
15A HEAD (LH±UPR)
(CANADA)
15A HEAD (RH±UPR)
(CANADA) ABS and
Traction ECU
Battery
[LOCATION](1): J/B No. 1 (See page
20)(2): R/B No. 2 (See page 19)(3): R/B No. 4 (See page 23)
20
19 22
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46
POWER SOURCE (Current Flow Chart)*1: USA
*2: CANADA
60
216
226
192178
226 90 144 134 216 102 202
208
212 90
167
A2 A15 C6 B2
B1
A10 A14 A12 A17A13 A23 A24 A25 A32 C11 B3 B4 B6 C3 C10C7
A21
Blower Resistor Auto Antenna Motor
And Relay A/C Magnetic Clutch
Alternator
A/C Control Assembly
A/C Power Transistor
A/T Indicator Light
(for Shift Lever) A/C Control SW and
Radio SWABS ECU
ABS and Traction ECUBrake Fluid Level SW
Blower Motor
Center Airbag Assembly Check Connector
Cornering Light LH
Cigarette Lighter Back±Up Light SW Buckle SW LHABS and Traction ECUCornering Light RH
190
226 22690
126
226 10168
134
144
178


* These are the page numbers of the first page on which the related system\
is shown.
The part indicated is located somewhere in the system, not necessarily o\
n the page indicated here. *Page Nos. of
Related Systems
Parts
Code or
Location
CB or Fuse
50A DEFOG
30A DOOR
30A POWER
15A STOP
15A ECU±B
10A MIR±HTR
10A HEATER
20A TURN
20A WIPER
10A GAUGE
15A ECU±IG
7.5A ENGINE
7.5A IGN
15A CIG
7.5A RADIO No.2
15A TAIL
7.5A PANEL
7.5A ST
15A TEL
10A DOME
20A RADIO No.1
25A HAZ±HORN
30A EFI
7.5 ALT SENCING
15A HEAD LH*1
15A HEAD RH*1
15A HEAD LH±LWR*2
15A HEAD RH±LWR*2
15A HEAD LH±UPR
15A HEAD RH±UPR
60A HEATER
7.5A TRAC
15A SEAT±HTR
Location
[LOCATION](1): J/B No. 1 (See page 20)(2): R/B No. 2 (See page 19)(3): R/B No. 4 (See page 23)
20
19 22
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