2000 LEXUS GS400 ignition

I04038
I04039
BE±42
± BODY ELECTRICALHEADLIGHT AND TAILLIGHT SYSTEM
2343 Author: Date:
2000 LEXUS GS300/GS400 (RM718U)8 ± Ground
Headlight dimmer switch HIGH beam or FLASHContinuity
1 ± GroundIgnition switch LOCK or ACCNo voltage
1 ± GroundIgnition switch ON or STARTBattery positive voltage
5 ± GroundEngine StopNo voltage
5 ± GroundEngine RunningBattery positive voltage
7 ± GroundConstantBattery positive voltage
9 ± GroundConstantBattery positive voltage
If circuit is specified, try replacing the relay with a new one.
If circuit is not as specified, inspect the circuits connected to oth-
er parts.
16. INSPECT AUTOMATIC LIGHT CONTROL
AUTO ON:
(a) Turn the ignition switch ON.
(b) Turn the light control switch to AUTO.
(c) Gradually cover the top of the sensor.
(d) Check the accessory lights and the headlights should turn
ON.
17. INSPECT AUTOMATIC LIGHT CONTROL
AUTO OFF:
(a) Gradually expose the sensor.
(b) Check the headlights and the accessory lights should turn
OFF.
18. INSPECT LIGHT±OFF CONDITION
(a) Turn the ignition switch ON.
(b) Gradually cover the top of the sensor.
Lights auto ON:
(c) Check that the lights go off under the following conditions.
(1) Light control switch is OFF.
(2) The area surrounding the sensor gets bright.
(3) The driver's door is opened with the ignition switch
OFF.

I01254
Wire Harness Side
4 3 2 1
± BODY ELECTRICALHEADLIGHT AND TAILLIGHT SYSTEM
BE±43
2344 Author: Date:
2000 LEXUS GS300/GS400 (RM718U)
19. INSPECT LIGHTS±ON CONDITION
(a) Open the driver's door while the ignition switch is OFF.
(b) Turn the light control switch to AUTO leaving the door
open and cover the top of the sensor, and verify that the
lights go on when the ignition switch is turned ON.
20. INSPECT AUTOMATIC LIGHT CONTROL SENSOR
CIRCUIT
Connector disconnected:
Disconnect the connector from the sensor and inspect the con-
nector on the wire harness side, as shown in the table.
Tester connectionConditionSpecified condition
3 ± GroundConstantContinuity
1 ± GroundIgnition switch LOCK or ACCNo voltage
1 ± GroundIgnition switch ONBattery positive voltage
4 ± GroundIgnition switch LOCK or ACCNo voltage
4 ± GroundIgnition switch ON5.2 ± 9.0 V
If circuit is as specified, perform the inspection on the following
page.
If the circuit is not as specified, inspect the circuit connected to
other parts.

I01255
1
2 3 4
From Back Side BE±44
± BODY ELECTRICALHEADLIGHT AND TAILLIGHT SYSTEM
2345 Author: Date:
2000 LEXUS GS300/GS400 (RM718U)
21. INSPECT AUTOMATIC LIGHT CONTROL SENSOR
CIRCUIT
Connector connected
Connect the wire harness side connector to the sensor and in-
spect wire harness side connector from the back side, as
shown.
HINT:

Ignition switch ON.

Light control switch AUTO.

Vehicle's surroundings are bright.
Tester connectionConditionSpecified condition
3 ± GroundConstantContinuity
1 ± GroundIgnition switch LOCK or ACCNo voltage
1 ± GroundIgnition switch ON9.5 V or more
Vehicle is under the direct sun light.
(Sensor is not covered)Taillight and Headlight are ON.
If circuit is as specified, try replacing the sensor with a new one.
If the circuit is not as specified, inspect the circuit connected to
other parts.

BE0HP±02
I03440
1 2 3
4 5 6
I05442
Wire Harness Side BE±50
± BODY ELECTRICALHEADLIGHT BEAM LEVEL CONTROL SYSTEM
2351 Author: Date:
2000 LEXUS GS300/GS400 (RM718U)
INSPECTION
1. INSPECT HEADLIGHT BEAM LEVEL CONTROL AC-
TUATOR RESISTANCE
(a) Check that continuity exists between terminals 2 and 5.
(b) Check that resistance exists between terminals, as
shown in the chart.
TerminalResistance (W)
2 ± 126 ± 30
2 ± 326 ± 30
2 ± 426 ± 30
2 ± 626 ± 30
5 ± 126 ± 30
5 ± 326 ± 30
5 ± 426 ± 30
5 ± 626 ± 30
If resistance value is not as specified, replace the actuator.
2. INSPECT HEADLIGHT BEAM LEVEL CONTROL ECU
CIRCUIT
Connector disconnected:
Disconnect the connector from the ECU and inspect the con-
nector on the wire harness side, as shown.
Tester connectionConditionSpecified condition
A1 ± A5Ignition switch OFF26 ± 30 W
A1 ± A6Ignition switch OFF26 ± 30 W
A1 ± A7Ignition switch OFF26 ± 30 W
A1 ± A8Ignition switch OFF26 ± 30 W
A4 ± B4Ignition switch ON and light control switch HEADBelow 1.5 V
B1 ± B3Ignition switch OFF3.5 ± 6.5 kW
B5 ± B7Ignition switch OFF3.5 ± 6.5 kW
A4 ± GroundIgnition switch OFFContinuity
If circuit is not as specified, perform the inspection on the follow-
ing pages.

I05442
I05441
13 m sec./ DivisionMotor operating 5V
/ Division
GND Pulse generation
± BODY ELECTRICALHEADLIGHT BEAM LEVEL CONTROL SYSTEM
BE±51
2352 Author: Date:
2000 LEXUS GS300/GS400 (RM718U)
3. INSPECT HEADLIGHT BEAM LEVEL CONTROL ECU
CIRCUIT
Connector connected:
Connect the connector from the ECU and inspect the connec-
tor, as shown in the table.
Tester connectionConditionSpecified condition
A1 ± A4Ignition switch ONBattery positive voltage
A1 ± A5Ignition switch ON, when stopping and bouncing
the vehicle.Pulse generation
A1 ± A6Ignition switch ON, when stopping and bouncing
the vehicle.Pulse generation
A1 ± A7Ignition switch ON, when stopping and bouncing
the vehicle.Pulse generation
A1 ± A8Ignition switch ON, when stopping and bouncing
the vehicle.Pulse generation
B2 ± B3Ignition switch ONApprox. 2.5 V
B6 ± B7Ignition switch ONApprox. 2.5 V
B1 ± B3
B5 ± B7Ignition switch ON5 V
If the circuit is not as specified, replace the ECU.
Reference INSPECTION USING OSCILLOSCOPE
HINT:
The correct waveform is as shown in the illustration.

BE0H0±06
I01353
Turn Signal LightsEngine Room No.1
Junction Block

TURN HAZ Fuse
Ignition Switch
Combination Switch

Turn Signal Switch
Hazard Warning Switch
Turn Signal Lights Turn Signal Lights
Driver Side Junction Block

GAUGE FuseCowl Side No.5
Junction Block

Turn Signal Flaher
± BODY ELECTRICALTURN SIGNAL AND HAZARD WARNING SYSTEM
BE±55
2356 Author: Date:
2000 LEXUS GS300/GS400 (RM718U)
TURN SIGNAL AND HAZARD WARNING SYSTEM
LOCATION
The vehicle shown in this illustration is ºGS400º.
All components of ºGS300º other than the ones used for engine are same as ºGS400º.

I04035
From Back Side
1 2 3
I04044
I04045
Wire Harness Side
± BODY ELECTRICALTURN SIGNAL AND HAZARD WARNING SYSTEM
BE±57
2358 Author: Date:
2000 LEXUS GS300/GS400 (RM718U)
3. INSPECT TURN SIGNAL SWITCH CIRCUIT
Connector connected:
Connect the wire harness side connector to the combination
switch and inspect the connector form the back side, as shown.
Tester connectionConditionSpecified condition
2 ± GroundIgnition switch ON and turn signal switch NeutralNo voltage
1 ± GroundIgnition switch ON and turn signal switch LeftBattery positive voltage e 0 V
3 ± GroundIgnition switch ON and turn signal switch RightBattery positive voltage e 0 V
If circuit is not as specified, inspect the circuits connected to oth-
er parts.
4. INSPECT HAZARD WARNING SWITCH CONTINUITY
Switch positionTester connectionSpecified condition
Switch OFF7 ± 10Continuity
Switch ON7 ± 8Continuity
Illumination circuit2 ± 3Continuity
If continuity is not as specified, replace the switch.
5. INSPECT HAZARD WARNING SWITCH CIRCUIT
(See page DI±814)
Disconnect the switch connector and inspect the connection on
the wire harness side, as shown.
Tester connectionConditionSpecified condition
8 ± GroundConstantContinuity
If circuit is not as specified, inspect the circuits connected to oth-
er parts.

I04046
Wire Harness Side BE±58
± BODY ELECTRICALTURN SIGNAL AND HAZARD WARNING SYSTEM
2359 Author: Date:
2000 LEXUS GS300/GS400 (RM718U)
6. INSPECT TURN SIGNAL FLASHER CIRCUIT
Disconnect the connector from the combination switch and in-
spect the connector on the wire harness side, as shown.
Tester connectionConditionSpecified condition
2 ± GroundConstantContinuity
3 ± GroundConstantContinuity
5 ± GroundTurn signal switch RIGHT or OFFNo continuity
5 ± GroundTurn signal switch LEFTContinuity
6 ± GroundTurn signal switch LEFT or OFFNo continuity
6 ± GroundTurn signal switch RIGHTContinuity
7 ± GroundConstantContinuity
8 ± GroundHazard warning switch OFFNo continuity
8 ± GroundHazard warning switch ONContinuity
1 ± GroundIgnition switch LOCK or ACCNo voltage
1 ± GroundIgnition switch ONBattery positive voltage
4 ± GroundConstantBattery positive voltage
If circuit is as specified, replace the relay.
If circuit is not as specified, inspect the circuits connected to oth-
er parts.