Isuzu D-Max / Isuzu Rodeo (TFR/TFS). Manual - part 1300

8–120 ELECTRICAL-BODY AND CHASSIS

TROUBLE SHOOTING

HEADLIGHT

1.

Both the headlights (high and low beam) do not light

Checkpoint

Trouble Cause

Countermeasure

Poor ground point contact

Repair the wiring

Ground point contact (C-2)

Poor switch contact or sw
faulty

Repair or replace the
combination switch

Combination switch
continuity

Poor relay contact or relay
faulty

Reinstall or replace the
lighting relay

Lighting relay

Open circuit between
battery positive terminal
and lighting relay

Repair open circuit

Voltage between 

5 X-1 - 

ground 

and 

2 X-1 - 

ground

Open circuit between
lighting relay and lighting
switch

Repair open circuit or
connector contact

Voltage between 1 C-42 -
ground

Open circuit

Repair open circuit

Wiring continuity between

7 C-42 -  C-2  and 

16 C-42 -  C-2 

NG

OK

OK

OK

OK

OK

NG

NG

NG

NG

NG

ELECTRICAL-BODY AND CHASSIS 8–121

2.

High or low beam does not light on both headlights

Checkpoint

Trouble Cause

Countermeasure

3.

RH (or LH) high and low beam does not light

Poor switch contact or
switch faulty

Repair or replace the
combination switch

Dimmer · passing switch
continuity

Open circuit between
headlight and dimmer ·
passing switch

Repair open circuit or
connector contact

Voltage between 

13 C-42 - ground and 

15 C-42 - ground

Poor installation or blown
fuse

Reinstall or replace fuse
No. EB-8 or No. EB-9

Fuse No. EB-8 (10A) or 
No. EB-9 (10A) (Relay and
fuse box)
(No. EB-9 RH, No. EB-8: LH)

Blown filament or air
leakage

Replace the headlight bulb

Headlight connector
continuity

Open circuit and/or poor
connector contact

Repair or replace the wire
and/or connector

Wiring continuity between
connector 3 C-19 -fuse No.
EB-9 or 3 C-26 -fuse No.
EB-8

NG

OK

OK

OK

NG

NG

NG

4.

High or low beam does not light on one headlight (RH or LH)

Blown filament

Replace the headlight
assembly

Headlight connector
continuity

Open circuit between
headlight and dimmer ·
passing switch

Repair open circuit or
connector contact

Wiring continuity between
headlight and dimmer ·
passing switch

OK

NG

NG

NG

8–122 ELECTRICAL-BODY AND CHASSIS

5.

Headlight does not go out

Checkpoint

Trouble Cause

Countermeasure

6.

Insufficient headlight brightness

Relay point fused

Replace the lighting relay

Lighting relay continuity
between connector 1  X-1
- 5  X-1 (Should be no
continuity)

Switch point fused or faulty

Replay the combination
switch

Lighting switch continuity
between connector 1 C-42
- 7 C-42 when switch is OFF
(Should be no continuity)

Lens dirty

Clean the light lens

Headlight lens

Bulb filament faulty

Replace the headlight bulb

Headlight bulb

Poor ground point contact

Repair the wiring

Dimmer · passing switch
wire continuity between con-
nector 16 C-42 -   C-2

NG

OK

OK

OK

NG

Switch point fused or faulty

Repair or replace the
combination switch

Dimmer · passing switch con-
tinuity between connector
14 C-42 - 16 C-42 when
switch is not operating
(Should be no continuity)

OK

NG

Short circuit

Repair short circuit

between 4  X-1 - 1  C-42

and 4  X-1 - 14 C-42

Check if headlight goes out
when connector  C-42  is
disconnected

OK

NG

NG

NG

NG

ELECTRICAL-BODY AND CHASSIS 8–123

7.

Passing light does not function when dimmer switch is operated

Checkpoint

Trouble Cause

Countermeasure

8.

Headlight beam does not change when dimmer switch is operated

Poor switch point contact

Repair or replace the
dimmer switch

Dimmer switch

Open circuit

Repair open circuit between
4 X-1 - 

14 C-42

Voltage between 
14 C-42 - ground (Should
be battery voltage present)

Loose beam lever or
foreign material in switch

Repair or replace the
dimmer switch

Dimmer switch

NG

OK

NG

NG