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.