Isuzu KB P190. Service manual — part 1320

8A-342 ELECTRICAL-BODY AND CHASSIS

CIRCUIT DIAGRAM 4JA1T (L) (LHD)

Sheet 4/4

RTW78AXF020701

ELECTRICAL-BODY AND CHASSIS 8A-343

TROUBLESHOOTING

SPEEDOMETER

1. Speedometer and odometer do not function

Checkpoint

Trouble

Cause

Countermeasure

Replace the vehicle speed

sensor

Vehicle speed sensor

malfunction

NG

Repair an open circuit in the

circuit or a poor connection at

the connectors

Continuity between the vehicle
speed sensor and the meter,
or the fuse C14 (10A) and the
ground

Open circuit or poor connector

contact

Replace the case baseboard

assy

Use a meter tester to check

the speedometer function

Speedometer malfunction

NG

NG

OK

OK

Check the vehicle speed

sensor output

(4 pulses/1 rotation)

2. Speedometer pointer fluctuates

(May be wide fluctuation)

Replace the vehicle speed
sensor, or repair an open
circuit in the circuit or a
connectors

Vehicle speed sensor

malfunction, or open circuit or

poor connector contact

NG

Replace the case baseboard

assy

Use a meter tester to check

the speedometer function

Speedometer malfunction

NG

OK

Check the speed sensor

output by using the

oscilloscope

8A-344 ELECTRICAL-BODY AND CHASSIS

3. Speedometer pointer jumps erratically

Checkpoint

Trouble

Cause

Countermeasure

Replace the vehicle speed
sensor, or repair an open
circuit in the circuit or a poor
connection at the connectors

Vehicle speed sensor

malfunction, or open circuit or

poor connector contact

NG

Replace the meter assembly

Use meter tester to check the

speedometer function

Speedometer malfunction

NG

OK

Check the vehicle speed

sensor output by using the

oscilloscope

Inspection of a Waveform by Oscilloscope
(Reference)

RTW780SH000101

1. Connect a resistance of 1.3 to 5k ohm (1.4W or more)

between the harness side connectors 40

B23

and 16

B24

of the meter.

2. Install a speedometer tester.

3. Turn on the starter SW.

RTW580SH002201

4. Check the waveform at the time when the vehicle speed is

at 60km/h.

4. Trip odometer does not reset

Replace the meter assembly

Faulty reset mechanism

NG

Check at other kilometer

figures given by meter tester
(Reset should be made to
zero kilometer)

ELECTRICAL-BODY AND CHASSIS 8A-345

TACHOMETER

1. Meter pointer fluctuates

(May be wide fluctuation)

Replace the meter assembly

Tachometer malfunction

NG

Use a meter tester to check

the tachometer function