Lexus GS300/400 (2000 year). Manual — part 75

BE0FY–09

I01377

Horn

Horn Switch

Engine Room No.1
Junction Block

HORN Fuse

Theft Deterrent Horn

Engine Room No.2
Junction Block

Horn Relay

–

BODY ELECTRICAL

HORN SYSTEM

BE–249

2550

HORN SYSTEM

LOCATION

The vehicle shown in this illustration is ”GS400”.

All components of ”GS300” other than the ones used for engine are same as ”GS400”.

BE0FZ–08

I04195

I04196

6

I04197

BE–250

–

BODY ELECTRICAL

HORN SYSTEM

2551

INSPECTION

1.

INSPECT HORN SWITCH

(a)

Disconnect the negative (–) terminal from the battery.

(b)

Remove the left and right covers from the steering wheel.

(c)

Using a torx socket wrench, loosen the 2 bolts.

(d)

Pull up the horn pad and place it on the steering column,
as shown.

HINT:
Do not disconnect the connector from the horn pad.
(e)

Disconnect the connector from the slip ring.

(f)

Check that no continuity exists between terminal 6 of the
connector and body ground.

(g)

Check that continuity exists between terminal 6 of the
connector and body ground when the horn contact plate
is pressed against the steering spoke assembly.

If continuity is not as specified, repair or replace the steering
wheel or wire harness as necessary.
(h)

Install the horn pad in place and using a torx socket
wrench, torque the 2 bolts.
Torque:

7.1 N·m (72 kgf·cm, 62 in.·lbf)

(i)

Install the left and right covers.

(j)

Connect the negative (–) terminal to the battery.

2.

INSPECT HORN OPERATION

Connect the positive (+) lead from the battery to the terminal
and negative (–) lead to the horn body and check that the horn
blows.
If operation is not as specified, replace the horn.
3.

INSPECT HORN SWITCH CIRCUIT
(See page

DI–806

)

I01200

2

1

3

5

2

5

1

3

–

BODY ELECTRICAL

HORN SYSTEM

BE–251

2552

4.

INSPECT HORN 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.
5.

INSPECT HORN RELAY CIRCUIT
(See page

BE–21

)

BE19B–01

–

BODY ELECTRICAL

TROUBLESHOOTING

BE–3

2304

TROUBLESHOOTING

PROBLEM SYMPTOMS TABLE

IGNITION SWITCH AND KEY UNLOCK WARNING SWITCH
This system uses the multiplex communication system, so check diagnosis system of the multiplex commu-
nication system before you proceed with troubleshooting.

Ignition Switch:

Symptom

Suspect Area

See page

Ignition switch is not set to each position.

4. Ignition switch

5. Power source circuit

BE–31

–

Key Unlock Warning Switch:

Symptom

Suspect Area

See page

Key unlock warning system does not operate.

(The buzzer does not sound when the driver’s door is opened with

the ignition OFF and key inserted)

1. Key Unlock Warning Switch

2. Door Courtesy Switch

3. Wire Harness

BE–31

BE–60

–

Key unlock warning system does not operate.

(The buzzer sounds when the ignition key is ACC or ON)

1. Ignition Switch

2. Wire Harness

BE–31

–

HEADLIGHT AND TAILLIGHT SYSTEM:
This system uses the multiplex communication system, so check diagnosis system of the multiplex commu-
nication system before you proceed with troubleshooting.
HINT:
To inspect the bulb and light control ECU, replace them with the ones working normally and judge whether
they work normally or not.

Symptom

Suspect Area

See page

”Automatic light control system” does not operate.

1. Automatic Light Control Sensor

2. Light Control Switch

3. Door Courtesy Switch

4. Wire Harness

5. Body No.2 ECU

BE–37

BE–37

BE–60

–

DI–820

Auto turn–off system does not operate when the driver’s door is

opened.

1. Drivers Door Courtesy Switch

BE–60

Auto turn–off system:

Headlight and taillight do not come on.

1. Body ECU No.2

2. Wire Harness

DI–820

–

Auto turn–off system:

Headlight and taillight stay on.

1. Body ECU No.2

2. Wire Harness

DI–820

–

USA:

Symptom

Suspect Area

See page

Only one headlight comes on.

1. Bulb

2. *Light Control ECU

3. Wire Harness

–

–

–

”LO–Beam” does not light (All).

1. Headlight Control Relay

2. *Light Control ECU

3. Wire Harness

BE–37

–

–

”LO–Beam” does not light (One side).

1. Bulb

2. H–LP L–LWR Fuse

3. H–LP R–LWR Fuse

4. *Light Control ECU

5. Wire Harness

–

BE–21

BE–21

–

–

”HI–Beam” does not light (All).

1. Headlight Dimmer Switch

2. Wire Harness

BE–37

–