Isuzu N-Series. Manual - part 1046

CAB AND CHASSIS ELECTRICAL 8-289

H-5

H-6, H-7, H-8

1

2

3

7

8

9

13

14 15

19

20 21

25

26 27

31

32 33

34

35

36

37

4

5

6

10

11 12

16

17 18

22

23 24

28

29 30

38

39 40

6

5

4

12

11 10

18

17 16

24

23 22

30

29 28

40

39 38

3

2

1

9

8

7

15

14 13

21

20 19

27

26 25

33

32 31

34

35

36

37

N8A5488E

1

2

1

2

1 2 3 4

5 6 7 8

9 10 11 12 13

14 15 16 17 18

2

1

2

1

4 3 2 1

8 7 6 5

13 12 11 10 9

18 17 16 15 14

H - 6

H - 7

H - 8

N8A5489E

8-290 CAB AND CHASSIS ELECTRICAL

Diagnosis

Quick Chart for Check Point
1. Speedometer

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

2. Tachometer

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

3. Coolant Temperature Gauge

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

Check point

Speedometer

Vehicle speed 

sensor

 Cable harness

Trouble
mode

1-1. Speedometer and odometer do not func-
tion

❍

(3)

❍

(1)

❍

(2)

1-2. Speedometer does not function
(odometer is normal)

❍

(1)

1-3. Odometer does not function
(Speedometer is normal)

❍

(1)

1-4. Speedometer needle fluctuates
(May be wide fluctuation)

❍

(3)

❍

(1)

❍

(2)

1-5. Speedometer needle jumps erratically

❍

(3)

❍

(1)

❍

(2)

Check point

Tachometer

Engine speed 

sensor

 Cable harness

Trouble
mode

2-1. Tachometer does not function

❍

(3)

❍

(1)

❍

(2)

2-2. Tachometer needle fluctuates
(May be wide fluctuation)

❍

(3)

❍

(1)

❍

(2)

2-3. Tachometer needle jumps erratically

❍

(3)

❍

(1)

❍

(2)

Check point

Meter 

ASM

Thermo 

meter

Thermo 

unit

Thermo 

seat

Cable 

harness

Trouble
mode

3-1. Coolant temperature gauge nee-
dle does not move

❍

(3)

❍

(4)

❍

(2)

❍

(1)

3-2. Coolant temperature gauge read-
ing is too low (or high)

❍

(4)

❍

(5)

❍

(3)

❍

(1)

❍

(2)

3-3. Needle overshoots (or goes up to
the “H” range)

❍

(3)

❍

(4)

❍

(1)

❍

(2)

CAB AND CHASSIS ELECTRICAL 8-291

4. Fuel Gauge

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

5. Warning/indicator Light

Check point

Meter ASM

Fuel gauge

Fuel tank 

unit

Cable 

harness

Trouble
mode

4-1. Fuel gauge needle does not move

❍

(3)

❍

(4)

❍

(2)

❍

(1)

4-2. Even when the tank is filled up with fuel,
the needle does not reach “F”

❍

(3)

❍

(4)

❍

(2)

❍

(1)

4-3. When the tank is not full of fuel, the nee-
dle overshoots (or goes to “F”)

❍

(3)

❍

(4)

❍

(2)

❍

(1)

Check point

Light 

bulb

Parking 

brake 

SW

Brake 

fluid 

SW

Oil 

pressure 

SW

Fuel 
tank 

unit

Vacuum 

SW

4WD 

SW

Sedim

enter 

SW

Seat 

belt 
SW

Cable 

harness

Trouble
mode

5-1. When the parking
brake lever is pulled, the
indicator light does not
light up

❍

(2)

❍

(1)

❍

(3)

5-2. Even when the park-
ing brake lever is
released, the indicator
light does not go off

❍

(1)

❍

(2)

5-3. While the engine
operating, the oil pressure
warning light does not go
off

❍

(2)

❍

(1)

5-4. Even when the tank is
full with fuel, the fuel warn-
ing light lights up

❍

(1)

❍

(2)

5-5. Even when the tank is
empty, the low fuel warn-
ing light does not light up

❍

(1)

❍

(2)

❍

(3)

5-6. Even when the float in
the water sedimenter goes
up above the drain warn-
ing level, the indicator light
does not light up

❍

(2)

❍

(1)

❍

(3)

5-7. Even when the brake
fluid is lower than speci-
fied level, the level warn-
ing light does not light up

❍

(1)

❍

(2)

❍

(3)

5-8. Even when the vac-
uum tank is empty vac-
uum warning buzzer does
not sound

❍

(1)

❍

(2)

8-292 CAB AND CHASSIS ELECTRICAL

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

1. Speedometer
1-1. Speedometer and Odometer Do Not Function

1-2. Speedometer Does Not Function (Odometer Is Normal)

• DOES THE VEHICLE SPEED SENSOR OUTPUT IN

NORMALLY?

• ARE THE CIRCUITS BETWEEN THE VEHICLE SPEED

SENSOR AND THE METER, AND THE FUSE (  F-16  10A)
AND THE GROUND NORMAL?

REPLACE THE VEHICLE SPEED SENSOR

YES

NO

YES

NO

REPAIR A POOR CONNECTION AT THE
CONNECTORS OR AN OPEN CIRCUIT IN
THE CIRCUIT

REPLACE THE SPEEDOMETER

N8A0299E

REPLACE THE SPEEDOMETER ASSEMBLY

N8A0300E