Isuzu KB P190. Manual — part 1232

7D1-54 TRANSFER CONTROL SYSTEM

Diagnosis from symptom

Check4WD lighting up

Step Action

Yes

No

1

Check what was done before the
trouble occurred.
Was the harness between the
transfer controller and actuator
disconnected with the ignition
kept ON for the purpose of
servicing the vehicle?
Or, was the ignition turned ON
(power supplied to the transfer
controller) with the harness of
the actuator removed?

If the power is supplied with the
actuator not connected, a faulty
position detection switch is
considered.
Clear the memory and trace this
chart from the beginning.

Go to step 2.

2

Is the ignition switch ON?

Go to step 3.

Turn the ignition switch ON and
trace this chart from the
beginning.

3

Does the transfer-related
indicators (4WD, 4Lo, Check
4WD, neutral) light up for 2
seconds when the ignition switch
is turned ON?

Go to step 4.

Indicator lamp burnt out.
Disconnected harness wire.
After repairing, trace this chart
from the beginning.

4

Has the harness between the
Check4WD indicator and
transfer controller GND shorted?

GND (body) short of the indicator
harness.
After repairing, trace this chart
from the beginning.

Go to step 5.

5

Check the continuity of harness
between the transfer controller
and transfer actuator. Check
the power short and GND short.
Check the GND harness of the
transfer actuator.
Is a trouble noticed?

Repair the harness, clear the
memory and trace this chart from
the beginning.

Go to step 6.

6

Check the limit switch of the
actuator.
Is a trouble noticed?

Failed actuator. Replace the
actuator, clear the memory and
trace this chart from the
beginning.

Clear the memory and trace this
chart from the beginning.
Failed controller.
Replace the controller, clear the
memory and trace this chart from
the beginning.

To check the operation after completing the repair and clearing the memory, shift between 2H and 4L at least 5
times.
To judge the condition more quickly, ask the customer what happens when the Check4WD lamp lights up.
When the position indicator blinks at a frequency of 4Hz immediately after trouble occurs, the position of failure
which the indicator shows may be limited.
(Since it indicates the situation immediately before detection of failure, whether the vehicle is running or at a
standstill, the possibility of failure around that point is high.)
Status of the transfer when the Check4WD lights up is not always the same. Immediately after failure occurs, 2H
can be operated.

TRANSFER CONTROL SYSTEM 7D1-55

Cannot shift from 2WD to 4H or 4L.
When shifting from 2H to other position, the indicator (4WD, 4Lo, Check4WD, neutral)
does not respond.

Step Action

Yes

No

1

Is the ignition switch ON?

Go to step 2.

Turn the ignition switch ON and
trace this chart from the
beginning.

2

Does the transfer-related
indicators (4WD, 4Lo, Check
4WD, neutral) light up for 2
seconds when the ignition switch
is turned ON?

Failed operation switch. Or,
Failed controller.

Indicator lamp burnt out.
Disconnected harness wire.
After repairing, trace this chart
from the beginning.

Even after correction step 1-1(*), 4WD indicator blinks at 4Hz and changes to 2H after 10
seconds.

Step Action

Yes

No

1

Is the ignition switch ON?

Go to step 2.

Turn the ignition switch ON and
trace this chart from the
beginning.

2

Does the transfer-related
indicators (4WD, 4Lo, Check
4WD, neutral) light up for 2
seconds when the ignition switch
is turned ON?

Go to step 3.

Indicator lamp burnt out.
Disconnected harness wire.
After repairing, trace this chart
from the beginning.

3

After 2 seconds, check that the
Check4WD lamp is ON or OFF.
Is the Check4WD lamp OFF?

Go to step 4.

Failed actuator position detection
switch (LS1, LS2, LS3, LS4,
GND).
Short or disconnection of harness
of this detection switch.
After repairing, trace this chart
from the beginning.

4

Press the 4H button.
Is sound of relay heard from the
transfer control?

Go to step 5.

Failed controller.
Replace the controller and trace
this chart from the beginning.

5

Is the sound of a running motor
heard?

Failed control system of the
transfer mechanism. Check and
repair and trace this chart from
the beginning.

Failed actuator motor.
Disconnected controller motor
drive output circuit, GND short
circuit. +B fuse blown out.
Disconnection of that harness.
After repairing, trace this chart
from the beginning.

*Before determining a trouble (Non-trouble mode)

7D1-56 TRANSFER CONTROL SYSTEM

Even after the correction step 1-2(*), the 4WD indicator still blinks at 2Hz when shifting
from 2H to 4H.

Step Action

Yes

No

1

Check the air pressure and wear
of all the tires. Is any trouble
noticed?

After adjusting the air pressure
and repairing the worn tires, try
the correction step 1-2(*).

Go to step 2.

2

Check the 4WD detection switch
on the transfer case, neutral
detection switch and each
harness. Is a trouble noticed?

4WD detection switch is open or
the harness failed.
The neutral detection switch is
closed or the harness GND is
shorted.
Replace or repair and then trace
this chart from the beginning.

Go to step 3.

3

Is there continuity in the harness
between the transfer controller
and front axle actuator? Has a
body short or disconnection
been detected?

Go to step 4.

Body short or disconnection of
the harness between the transfer
controller and front axle actuator.
After repairing, trace this chart
from the beginning.

4

Is trouble detected in the axle
detection harness between the
axle actuator and transfer
controller?

Disconnected harness.
After repairing trace this chart
from the beginning.

Malfunction of axle actuator.
Refer to the paragraph of the axle
disconnect.
After repairing, trace this chart
from the beginning.

*Before determining a trouble (Non-trouble mode)

Note:
Vehicles with manual hub and rigid hub don’t have axle actuator.
When the above-mentioned procedure is followed, check the harness between the axle dummy output terminal and
the axle switch input terminal of the transfer controller, instead of axle actuator.

TRANSFER CONTROL SYSTEM 7D1-57

After operation, indicator of target position blinks for 1.5 sec. at 2Hz, return to 2H
condition (4WD indicator going out)

Step Action

Yes

No

1

Keep pressing the 4H button
(about 10 seconds).
Does the 4WD indicator blink at
2Hz for 15 seconds and then
blink at 4Hz?

Failed actuator motor.
Disconnection of controller motor
drive output circuit, or GND short.
+B fuse blown out.
Disconnection of that harness.
After repairing, trace this chart
from the beginning.

Go to step 2.

2

Press the 4H button.
Is the sound of relay heard from
the transfer controller?

Go to step 3.

Failed controller.
Replace the controller and trace
this chart from the beginning.

3

Is the sound of running motor
heard?

Failed control system of the
transfer mechanism. Check and
repair and trace this chart from
the beginning.

Failed actuator motor.
Disconnection or GND short of
controller motor drive output
circuit.
After repairing, trace this chart
from the beginning.