LEXUS SC400 1991 Service Repair Manual

IGNITION SWITCH
Description
The ignition switch is supplied with power from the battery via a fusible l\
ink. Power is supplied to each fuse
and relay according to the position of the switch, whether ªCCº ``ONº or ªSTARTº. The key unlock warning
switch, which detects the set condition of the key, is built into this switch.
Parts Location
Wiring and Connector Diagrams
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BODY ELECTRICAL SYSTEM Ignition SwitchBE±25
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Parts Inspection
(Ignition Switch and Key Unlock
Warning Switch)
REMOVAL AND INSTALLATION OF
IGNITION SWITCH AND KEY UNLOCK
WARNING SWITCH
1. DISCONNECT BATTERY TERMINALSCAUTION: Work must be started after approx. 20 se-
conds or longer from the time the ignition switch is
turned to the ºLOCKº position and negative (±) terminal
cable is disconnected from the battery.
2. REMOVE FOLLOWING PARTS: (See page BO±112)
w No. 1 under cover
w No. 1 lower finish panel
w Console box assembly
w Instrument panel lower center
3. REMOVE IGNITION SWITCH (a) Disconnect connector.
(b) Remove three screws and the switch from the keycylinder and wire harness clamp.
4. INSTALL IGNITION SWITCH For installation, follow the removal procedure in reverse.
INSPECTION OF IGNITION SWITCH AND
KEY UNLOCK WARNING SWITCH
1. INSPECT IGNITION SWITCH(Switch continuity)
Inspect the switch continuity between terminals.
Terminal
Switch position LOCKACC
ON
START
If continuity is not as specified, replace the switch.
BE±26
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BODY ELECTRICAL SYSTEM Ignition Switch
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(Switch circuit)
Connect the switch connector and inspect the connector on
the wire harness side from the back side as shown.
Check forTester connectionConditionSpecified value
Voltage2±GroundIgnition switch turned to ONBattery voltage
3±GroundIgnition switch turned to ACC or ON
4±GroundConstant
5±GroundIgnition switch turned to START
6±GroundIgnition switch turned to ON
11±GroundConstant
If circuit is not as specified, inspect the switch or refer to
BE±25 wiring diagram and inspect the circuits connected to
other parts.
2. INSPECT KEY UNLOCK WARNING SWITCH
(Switch continuity)
Inspect the switch continuity between terminals.
Terminal
Switch position
ON
OFF
(Ignition Key removed)
(Ignition Key set)
If continuity is not as specified, replace the switch.
(Switch circuit)
Connect the switch connector and inspect the connector on
the wire harness side from the back side as shown.
Check forCheck connectionConditionSpecified value
Continuity10±GroundIgnition key removedNo continuity
Ignition key setContinuity
9±GroundConstantContinuity
If circuit is not as specified, inspect the switch or wire harness.
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BODY ELECTRICAL SYSTEM Ignition SwitchBE±27
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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.
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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
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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
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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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