Lexus RX300 (MCU15). Service manual — part 121

BE1YF–01

I19121

Hi beam

AUTO

HEAD

TAIL

OFF

Flash

7

8

17

16

14 13

12

N21563

Wire Harness Side

2

1

3 4 5

6

7 8

13 14 15 16

9 10 11 12

17

–

BODY ELECTRICAL

HEADLIGHT AND TAILLIGHT SYSTEM

BE–31

LEXUS RX300 (RM785E)

INSPECTION

1.

INSPECT LIGHT CONTROL SWITCH CONTINUITY

Switch position

Tester connection

Specified condition

OFF

–

No continuity

TAIL

14 – 16

Continuity

HEAD

13 – 14 – 16

Continuity

AUTO

12 – 16

Continuity

If continuity is not as specified, replace the switch.
2.

INSPECT HEADLIGHT DIMMER SWITCH CONTINU-
ITY

Switch position

Tester connection

Specified condition

Low beam

16 – 17

Continuity

High beam

7 – 16

Continuity

Flash

7 – 8 – 16

Continuity

If continuity is not as specified, replace the switch.

3.

INSPECT COMBINATION SWITCH CIRCUIT

Connect the wire harness side connector to the combination
switch and inspect wire harness side connector from the back
side.

Light Control Switch:

Tester connection

Condition

Specified condition

16 – Ground

Constant

Continuity

12 – Ground

Light control switch OFF, TAIL or HEAD

No voltage

12 – Ground

Light control switch AUTO

Battery voltage

13 – Ground

Light control switch OFF or TAIL

No voltage

13 – Ground

Light control switch HEAD

Battery voltage

14 – Ground

Light control switch OFF

No voltage

14 – Ground

Light control switch TAIL or HEAD

Battery voltage

Z09181

3

4

3

4

1

2

2

1

N14863

1

2

3

5

5

3

1

2

Z08559

2

1

3

4

4

3

2

1

BE1838

BE1840

BE–32

–

BODY ELECTRICAL

HEADLIGHT AND TAILLIGHT SYSTEM

LEXUS RX300 (RM785E)

Headlight Dimmer Switch:

Tester connection

Condition

Specified condition

7 – Ground

Headlight dimmer switch Low Beam

No voltage

7 – Ground

Headlight dimmer switch High Beam or Flash

Battery voltage

8 – Ground

Headlight dimmer switch Low Beam or High

Beam

No voltage

8 – Ground

Headlight dimmer switch Flash

Battery voltage

17– Ground

Headlight dimmer switch High Beam or Flash

No voltage

17– Ground

Headlight dimmer switch Low Beam

Battery voltage

If the circuit is not as specified, inspect the circuit connected to
other parts.

4.

INSPECT HEADLIGHT CONTROL RELAY CONTINU-
ITY

Condition

Tester connection

Specified condition

Constant

3 – 4

Continuity

Apply B+ between

terminals 3 and 4.

1 – 2

Continuity

If continuity is not as specified, replace the relay.
5.

INSPECT HEADLIGHT CONTROL RELAY CIRCUIT
(See page BE–18)

6.

INSPECT TAILLIGHT CONTROL RELAY CONTINUITY

Condition

Tester connection

Specified condition

Constant

1 – 2

Continuity

Apply B+ between

terminals 1 and 2.

3 – 5

Continuity

If continuity is not as specified, replace the relay.
7.

INSPECT TAILLIGHT CONTROL RELAY CIRCUIT
(See page BE–18)

8.

INSPECT DRL NO.2 RELAY CONTINUITY

Condition

Tester connection

Specified condition

Constant

3 – 4

Continuity

Apply B+ between

terminals 3 and 4.

1 – 2

Continuity

If continuity is not as specified, replace the relay.
9.

INSPECT DRL NO.2 RELAY CIRCUIT
(See page BE–18)

I04495

I04496

I01254

Wire Harness Side

4

3

2

1

I01255

1

2

3

4

–

BODY ELECTRICAL

HEADLIGHT AND TAILLIGHT SYSTEM

BE–33

LEXUS RX300 (RM785E)

10.

Auto ON:
INSPECT AUTOMATIC LIGHT CONTROL

(a)

Turn the ignition switch ON.

(b)

Turn the light control switch to AUTO.

(c)

Gradually cover the top of the sensor.

(d)

Verify that the accessory lights and the headlights turn
ON.

11.

Auto OFF:
INSPECT AUTOMATIC LIGHT CONTROL

(a)

Gradually expose the sensor.

(b)

Verify that the headlights and the accessory lights turn
OFF.

12.

INSPECT LIGHT–OFF CONDITION

(a)

Turn the ignition switch ON.

(b)

Gradually cover the top of the sensor.
Lights auto ON:

(c)

Verify that the lights will go out when light control switch
position is OFF or the area surrounding the sensor gets
bright or open the driver’s door while the ignition switch is
OFF.

13.

INSPECT LIGHTS–ON CONDITION

(a)

Open the driver’s door while the ignition switch is OFF.

(b)

Turn the light control switch to AUTO the door open and
cover the top of the sensor, and verify that the lights go on
when the ignition switch is turned ON.

14.

INSPECT AUTOMATIC LIGHT CONTROL SENSOR
CIRCUIT

Disconnect the connector from the sensor and inspect the con-
nector on the wire harness side, as shown in the chart.
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.

15.

INSPECT AUTOMATIC LIGHT CONTROL SENSOR
CIRCUIT

Connect the wire harness side connector to the sensor and in-
spect wire harness side connector from the back side, as
shown.
HINT:

S

Ignition switch ON.

S

Light control switch OFF.

S

Vehicle’s surroundings are bright.

BE–34

–

BODY ELECTRICAL

HEADLIGHT AND TAILLIGHT SYSTEM

LEXUS RX300 (RM785E)

Tester connection

Condition

Specified condition

3 – Ground

Constant

Continuity

1 – Ground

Ignition switch LOCK or ACC

No voltage

1 – Ground

Ignition switch ON

9.5 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.