Isuzu N-Series. Manual - part 1009

CAB AND CHASSIS ELECTRICAL 8-141

Diagnosis

Quick Chart for Check Point
1. Headlight

Notice:
Figure in parenthesis “( )” indicates the order of inspection.

Check point

Fuse

Fus-

ible 
link

Head-

light 

relay

Light-

ing 

SW

Dim-

mer / 

Pass-

ing 

SW

Dim-

mer 

relay

Headlight 

bulb

Cable 

har-

ness

F-6
F-8

(10 A)

F-23

(10 A)

F-24

(10 A)

FL-4

(30A)

LH

RH

Trouble 
mode

1-1. Both Head-
lights inopera-
tive

❍

(2)

❍

(1)

❍

(4)

❍

(3)

1-2. Headlight 
on the left (or 
right) side inop-
erative

❍

(1)

❍

((1))

❍

(2)

1-3. Headlight in 
low-beam inop-
erative

❍

(1)

❍

(2)

1-4. Headlight in 
high-beam inop-
erative

❍

(1)

❍

(2)

1-5. Headlight 
on the left (or 
right) side in low 
(or high)-beam 
inoperative

❍

(1)

❍

((1))

❍

(2)

1-6. Headlight 
beam does not 
change

❍

(1)

❍

(2)

❍

(3)

❍

(4)

1-7. Headlights 
remain on when 
the lighting 
switch turned off

❍

(1)

❍

(2)

❍

(3)

1-8. Headlights 
come on with 
the lighting SW 
at the clearance 
light position

❍

(1)

8-142 CAB AND CHASSIS ELECTRICAL

2. Fog Light

Notice:
Figure in parenthesis “( )” indicates the order of inspection.

3. Cornering Light

4. Rear Fog Light

Check point

Fuse

F-6 (10 A): 4JH1,4JB1, 4JB1-

TC

F-8 (10 A): 24V, 4HG1-T (12 V)

Tail-
light 

relay

Fog 

light 

SW

Fog light 

bulb

Cable 

harness

LH

RH

Trouble 
mode

2-1. Both fog lights inopera-
tive (while lighting switch is 
on)

❍

(1)

❍

(2)

❍

(3)

❍

(4)

2-2. Fog light on the left (or 
right) side inoperative (while 
lighting switch is on)

❍

(1)

❍

((1))

❍

(2)

2-3. Fog lights remain on

❍

(1)

❍

(2)

❍

(3)

Check point

Fuse

Cornering 

light SW

Cornering 

light bulb

Cornering 

light relay

Cable 

harness

F-6 : 4JH1,4JB1,4JB1-

TC

F-8 : 24V,4HG1-T(12V)

F-16

(10 A)

Trouble 
mode

3-1. Both corner-
ing lights inoper-
ative

❍

(2)

❍

(1)

❍

(5)

❍

(3)

❍

(4)

3-2. Cornering 
light on the left 
(or right) side 
inoperative

❍

(2)

❍

(1)

❍

(3)

3-3. Cornering 
light remains on 
even when steer-
ing wheel is in 
the straight 
ahead position

❍

(1)

Check point

Fuse

F-27 (15 A)

Rear fog 

light SW

Rear fog 

light relay

Rear fog 

light bulb

Cable 

harness

Trouble 
mode

4-1. Rear fog light inoperative 
(while headlight is ON)

❍

(2)

❍

(4)

❍

(3)

❍

(1)

❍

(5)

CAB AND CHASSIS ELECTRICAL 8-143

1. Headlight
1-1. Both Headlights Inoperative

1-2. Headlight on The Left (or Right) Side Inoperative

N8A0118E

IS FUSE  F-24  OR  F-23  (10A) NORMAL?

YES

NO

REPLACE THE FUSE

REPAIR A POOR CONNECTION AT THE CONNECTORS
OR AN OPEN CIRCUIT BETWEEN FUSE  F-24  (10A) AND 
3  B-4  (OR 3  B-148 ) OR FUSE  F-23  (10A) AND 3  B-73
(OR 3  B-150 )

•

N8A0119E

8-144 CAB AND CHASSIS ELECTRICAL

1-3. Headlight in Low-beam Inoperative

1-4. Headlight in High-beam Inoperative

N8A0120E

• IS THE DIMMER RELAY NORMAL?

• DISCONNECT THE DIMMER / PASSING SW

CONNECTOR

• IS THERE ANY CONTINUITY BETWEEN SW SIDE

CONNECTORS 4  B-70  AND 10  B-70  WHEN THE SW IS
AT HIGH-BEAM POSITION?

YES

NO

REPLACE THE RELAY

REPAIR A POOR CONNECTION AT THE CONNECTORS
OR AN OPEN CIRCUIT BETWEEN 1  X-6  AND 2  B-74  

YES

NO

REPAIR OR REPLACE THE SW

• DISCONNECT THE HEADLIGHT RELAY

• IS THERE ANY CONTINUITY BETWEEN CHASSIS SIDE

CONNECTORS 10  B-70  AND 5  X-3  ?

YES

NO

REPAIR A POOR CONNECTION AT THE
CONNECTORS OR AN OPEN CIRCUIT
BETWEEN 10  B-70  AND 5  X-3

IS FUSE   F-6  OR   F-8  CONNECTED?

YES

NO

REPLACE THE FUSE

•

N8A0121E