ISUZU TF SERIES 2004 Workshop Manual

ELECTRICAL-BODY AND CHASSIS 8A-253

CIRCUIT DIAGRAM 4JA1-L (LHD) Sheet 2/3




RTW48AXF004701

8A-254 ELECTRICAL-BODY AND CHASSIS

CIRCUIT DIAGRAM 4JA1-L (LHD) Sheet 3/3




RTW48AXF004901

ELECTRICAL-BODY AND CHASSIS 8A-255
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 RHD: C-5 (15A)
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-256 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 case baseboard
assy

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
1. Connect a resistance of 1.3 to 5k ohm (1.4W or more) between the harness side connectors 30 B-24 and 9

B-24 of the meter.


2. Install a speedometer tester.
2. Turn on the starter SW.
3. Check the waveform at the time when the vehicle speed is at 60km/h.





4. Trip odometer does not reset


Replace the case baseboard
assy

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-257
TACHOMETER
1. Tachometer does not function when engine is running

Checkpoint Trouble Cause Countermeasure

Replace the tacho sensor, or
repair open circuit or
connector contact Tacho sensor malfunction, or
open circuit or poor connector
contact
NG

Replace the case baseboard
assy

Tachometer function

Tachometer malfunction
NG OK
Pulse between connector
B-24 and the ground when
engine is running (Should be
pulse present)



2. Meter pointer fluctuates
(May be wide fluctuation)


Replace the case baseboard
assy

Tachometer malfunction
NG
Use a meter tester to check
the tachometer function

8A-258 ELECTRICAL-BODY AND CHASSIS
TEMPERATURE GAUGE AND THERMO UNIT
1. No temperature indicates at all

Checkpoint Trouble Cause Countermeasure


Replace the thermo unit

Thermo unit malfunction
NG

Replace the case baseboard
assy

Gauge function
1. Disconnect the unit
connector then connect
3.4W bulb to wire harness
side with ground
2. Check indicating point
when starter SW. is ON
position (Temperature
should indicate)

Gauge malfunction


Repair open circuit or
connector contact
Continuity between 1 E-19
(C24NE & 6VE1:
E-85 ) and
13
B-24


Open circuit or poor connector
contact
NG NG OK
OK
Thermo unit continuity
between connector
E-19
(C24NE & 6VE1:
E-85 ) and
the ground



2. Temperature gauge incorrect readings in all ranges


Replace the thermo unit

Thermo unit malfunction
NG
Thermo unit resistance
between connector 1
E-19
(C24NE & 6VE1:
E-85 ) and
the ground when
disconnecting the connector
(Specified resistance should
indicate)

ELECTRICAL-BODY AND CHASSIS 8A-259
FUEL GAUGE AND FUEL TANK UNIT
1. No fuel level indicates at all

Checkpoint Trouble Cause Countermeasure


Replace the tank unit

Open circuit inside the tank
unit
NG Thermo unit malfunction

Replace the case baseboard
assy

Fuel gauge function
1. Disconnect the tank unit
connector then connect
3.4W bulb to wire harness
side
2. Check indicating point
when starter SW. is ON
position (Fuel level should
indicate)

Gauge malfunction


Repair open circuit or
connector contact
Continuity between
connectors 14
B-24 and 3

F-2

Open circuit or poor connector
contact
NG NG OK
OK

Tank unit continuity between
connector 3
F-2 and ground




2. Fuel gauge gives incorrect readings in all ranges

Replace the tank unitTank unit malfunction NG
Tank unit resistance position
with the float at checking
points (Specified resistance
should indicate)

8A-260 ELECTRICAL-BODY AND CHASSIS
WARNING AND INCIDATOR LIGHT
1. When the parking brake lever is pulled, the indicator light does not light up

Checkpoint Trouble Cause Countermeasure


Replace or reinstall the bulb

Bulb burned out or loose
contact
NG

Adjust or replace the parking
brake SW.

Parking brake SW. installation
position and function

Incorrect SW. adjustment or
poor SW. point contact


Repair open circuit or
connector contact
Continuity between the
parking brake SW. connector
1
C-39 (Lever: 1 R-4) and
9
B-23

Open circuit or poor connector
contact
NG NG OK
OK

Brake indicator light bulb
continuity


Replace the parking brake
SW.
Continuity between the
parking brake SW. connector
1
C-39 (Lever: 1 R-4) and
the ground when the parking
brake is operated

Parking brake SW.
malfunction
NG OK

ELECTRICAL-BODY AND CHASSIS 8A-261
2. Even when the parking brake lever is pulled, the indicator light does not go off

Checkpoint Trouble Cause Countermeasure

Adjust the SW. installation
position or replace the parking
brake SW. Incorrect the parking brake
SW. adjustment or brake SW.
faulty
NG Thermo unit malfunction
Replace the brake fluid level
SW., or vacuum SW., or
repair a short circuit between
the parking brake SW.
connector 1
C-39
(Lever: 1
R-4) and 9 B-23
or the brake fluid level SW.
connector 2
C-37 and 9
B-23, (or the vacuum SW.
connector 1
C-38 and 9
B-23 : 4JH1-TC ONLY)
Check to see if the indicator
light goes off when the parking
brake SW. connector 1
C-39
(Lever: 1
R-4) is
di t d
Brake fluid level SW. or
vacuum SW. faulty or short
circuit
NG OK

Parking brake SW. installation
position and function




3. Oil pressure warning light does not go off while engine is running


Refer to ENGINE Section

Refer to ENGINE Section
NG Thermo unit malfunction

Repair a short circuit between
1
E-1 and 3 B-24

Check to see the warning light
goes off when the oil pressure
SW. connector
1
E-1 is disconnected


Short circuit


Replace the oil pressure unit
(or the oil pressure SW.)
Continuity between the oil
pressure SW. connector
1
E-1 and the body ground
when the engine is operating


Oil pressure unit (or oil
pressure SW) faulty
NG NG OK
OK

Engine oil pressure

8A-262 ELECTRICAL-BODY AND CHASSIS
REMOVAL AND INSTALLATION

This illustration is based on RHD model
METER ASSEMBLY
Removal
1. Meter Cluster Assembly

Refer to the removal steps of “INSTRUMENT PANEL” in
Section 10 “CAB”
2. Meter Assembly

Remove three screws of the meter assembly.

Disconnect the meter connectors.






Installation
Follow the removal procedure in the reverse order to install the
meter.
Pay close attention to the important points mentioned in the
following paragraphs.



Connector
Be absolutely sure that the meter connectors are securely
connected.
This will prevent a poor contact and an open circuit.



Wire Harness
Do not pinch the wire harness between the cluster and the
meter hood during the meter assembly installation procedure.
Wire damage will result.