light LEXUS SC400 1991 Service Repair Manual

No.Part NameRelated Systems or Parts
22MAIN
Upstream of ALT±S and EFI Fuse
23AM2
Charging System
Engine23AM2
AIR±BAG System
24ABS NO. 2
ABS and TRAC
25INJ
Charging System
Engine25INJ
AIR±BAG System
26DEF
Defogger System

Power Seat System
Sliding Roof System

A/C System
Liquid Crystal Inner Mirror System
27DOME
Combination Meter System
Interior Light System27DOME
ABS and TRAC
Wireless Door Lock Control System

Cruise Control System
Auto±Tilt away Steering

Theft Deterrent System
28EFI
Engine
29HAZ HORN
Turn Signal and Hazard Warning Light System29HAZ±HORN
Horn System
30RADIO NO. 1
Audio System
31TEL
TEL System
32ALT±S
Charging System
33TRAC
ABS and TRAC
34HEAD (RH±LWR)
Headlight System
35HEAD (LH±LWR)
Headlight System
36HEAD (RH±UPR)
Headlight System
37HEAD (LH±UPR)
Headlight System
38HTR
Blow Motor
±
BODY ELECTRICAL SYSTEM Power SourceBE±19
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Inspection of Power Source Circuit
INSPECTION OF JUNCTION BLOCK NO. 1
1. INSPECT FUSE CIRCUITRemove the fuse from the junction block and inspect the con-
nector on junction block side as shown.
FuseCheck forTester connectionConditionSpecified value
IGNVoltage1±GroundIgnition switch turned to ONBattery voltage
ST
g
4±GroundIgnition switch turned to START
yg
WIPER5±GroundIgnition switch turned to ON
HTR8±Ground
g
ENGINE9±Ground
RADIO NO. 211±GroundIgnition switch turned to ACC or ON
CIG14±Ground
g
STOP15±GroundConstant
TURN18±GroundIgnition switch turned to ON
MIR HTR20±GroundIgnition switch turned to ON and defogger
switch turned to ON
PANEL21±GroundLight control switch turned to TAIL or HEAD
and *Engine Running
ECU±B27±GroundConstant
GAUGE29±GroundIgnition switch turned to ON
ECU±IG32±Ground
g
TAIL33±GroundLight control switch turned to TAIL or HEAD
and *Engine Running
DOOR35±GroundConstant
IG SW38±Ground
POWER39±Ground
If the circuit is not as specified, refer to BE±15 wiring diagram
and inspect the circuits connected to other parts.
BE±20
±
BODY ELECTRICAL SYSTEM Power Source
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FuseCheck forTester ConnectionConditionSpecified value
HTRVoltage(15)±GroundConstantBattery voltage
DEF(17)±Ground
DOME(24)±Ground
EFI(26)±Ground
HAZ±HORN(28)±Ground
RADIO NO. 1(30)±Ground
TEL(32)±Ground
ALT±S(34)±Ground
TRAC(36)±Ground
HEAD (RH±LWR)(38)±GroundLight control switch turned to TAIL or
HEAD (LH±LWR)(40)±GroundHEAD and *ENGINE running
HEAD (RH±UPR)(44)±GroundLight control switch turned to HEAD and
HEAD (LH±UPR)(46)±Grounddimmer switch turned to HI or FLASH
If the circuit is not as specified, refer to BE±15 wiring diagram
and inspect the circuits connected to other parts.
2. INSPECT RELAY CIRCUIT Remove the relay from the relay block and inspect the con-
nector on relay block side as shown.
RelayCheck forTester connectionConditionSpecified value
EFIVoltage(4)±GroundConstantBattery voltage
ST(10)±Ground
(11)±Ground
DIM(15)±GroundLight control switch turned to TAIL or HEAD
(16)±Groundand *Engine running
IG2(18)±GroundConstant
HTR(24)±Ground
(25)±Ground
H±LP(28)±Ground
(30)±Ground
DEF(34)±Ground
(35)±Ground
If the circuit is not as specified, refer to BE±15 wiring diagram
and inspect circuits connected to other parts.
BE±22
±
BODY ELECTRICAL SYSTEM Power Source
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LIGHTING SYSTEM
BE±28±
BODY ELECTRICAL SYSTEM Lighting System
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(HEADLIGHT SYSTEM)
Description ± Headlight System
The component parts of this system and their function are described in the \
following table.
Parts NameFunction
Light Control SwitchGrounds current from the headlight control relay and taillight control r\
elay via the
integration relay, switching each relay and supplying current to the appropriate bulbs
accordance with the switch position.
Dimmer SwitchGrounds current from the dimmer relay in accordance with the switch posi\
tion, turning
on the ºLO±Beamº or ºHI Beamº lights. In the case of º\
FLASHº it turns the heading
control relay and turns on the ºHI Beamº lights.
Headlight Control
RelayTurned on by signals from the light control switch, dimmer switch and run\
ning light
relay and supplies current to each bulb or headlight dimmer relay.
Headlight
Dimmer RelayReceives current from the headlight control relay, which switches the relay according
to the position of the dimmer switch and sends current to the headlight \
ºLO±Beamº
or ºHI Beamº.
Integration RelayCarries out ºLight Auto Turn±offº of the headlights and taillights and cuts off current to
the light control switch in accordance with signals from the GAUGE fuse \
and courtesy
switch.
Door Courtesy
Switch/Driver 'sDetects when the door is open and sends the appropriate signals to integ\
ration relay.
(Light Auto Turn±Off System)
Parking Brake
Switch
(CANADA)Detects when the parking brake lever is released and sends the appropria\
te signals to
daytime running light relay.
±
BODY ELECTRICAL SYSTEM Lighting SystemBE±29
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System Description ± Headlights
DAYTIME RUNNING LIGHT SYSTEM
The Daytime Running Light (DRL) system is activated when engine is started (However, if the parking brake
lever is engaged when the engine is started, the DRL will not light up a\
fter the engine has started. Once the
parking brake is released, the DRL will then light up and will remain on regardless of operation of\
the parking
brake lever).
The DRL remain on until the ignition switch is turned off.
BE±30±
BODY ELECTRICAL SYSTEM Lighting System
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Operation example (Current flow table)
1. Daytime Running Light Lights Up
SwitchPosition
Ignition switchON (Engine running)
Light Control SwitchOFF
Headlight Dimmer SwitchLO or HI
Condition: Battery Voltage " (3) , (14)
2. Taillight Lights Up
SwitchPosition
Ignition SwitchOFF or ON
Light Control SwitchTAIL
Headlight Dimmer SwitchLO or HI
Condition: Battery Voltage " (3)
Continuity (16) " (17) " Ground
3. Headlight LO±Beam Lights Up
SwitchPosition
Ignition SwitchOFF or ON
Light Control SwitchHEAD
Headlight Dimmer SwitchLO
Condition: Battery Voltage " (3)
Continuity (16) " (17) " Ground
(18) " (17) " Ground
±
BODY ELECTRICAL SYSTEM Lighting SystemBE±31
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4. Headlight HI±Beam Lights Up
SwitchPosition
Ignition SwitchOFF or ON
Light Control SwitchHEAD
Headlight Dimmer SwitchHI
Condition: Battery Voltage " (3)
Continuity (20) " (21) " Ground
(18) " (17) " Ground
(16) " (17) " Ground
5. Headlight Flash
SwitchPosition
Ignition SwitchOFF or ON
Light Control SwitchOFF or TAIL or HEAD
Headlight Dimmer SwitchFLASH
Condition: Battery Voltage " (3)
Continuity (19) " (21) " Ground
(20) " (21) " Ground
BE±32±
BODY ELECTRICAL SYSTEM Lighting System
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Parts Location ± Headlight System
±
BODY ELECTRICAL SYSTEM Lighting SystemBE±33
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Wiring Diagram ± Headlight System
BE±34±
BODY ELECTRICAL SYSTEM Lighting System
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