Isuzu KB P190. Manual - part 1233

7D1-58  TRANSFER CONTROL SYSTEM 

Transfer cannot shift to another position (Except “Check 4WD” failure). 

When shifting to another position, indicator (4WD, 4Lo, Check4WD, neutral) does not 
respond (Current condition keeping). 

Step Action 

Yes 

No 

1 

Is the ignition switch ON? 

Go to step 2. 

Failed indicator and harness 
(When lighting). 
After repairing, 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. 

All indicators are burnt out 
(Check for GND short circuit 
between the indicator and 
transfer controller). 
Disconnected harness wire. 
After repairing, trace this chart 
from the beginning. 

3 

Press the other positions button. 
Is the sound of relay heard from 
under the seat, and the sound of 
a running motor heard? 

Failed controller. 
After replacing the controller, 
trace this chart from the 
beginning. 

*Failed operation switch.  Or 
harness for the operation switch 
has disconnected or shorted. 

* The operation switch is an analog type switch which reads the internal composite resistance value at the time of 

operation.  If an abnormal value is detected, it is kept at the home position (The position before operating it). 

 
 

TRANSFER CONTROL SYSTEM  7D1-59 

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

Step Action 

Yes 

No 

1 

Check all the tires for air 
pressure and wear.  Is any 
trouble detected? 

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

Go to step 2. 

2 

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

4WD detection switch is closed 
or the GND short of harness. 
The neutral detection switch is 
closed or the harness GND has 
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 axle actuator? 
Has a short or disconnection 
been detected? 
Is the connection incorrect? 

Go to step 4. 

Body short, disconnection or 
incorrect connection of the 
harness between the transfer 
controller and 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? 

GND short of harness 

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

 

*Before determining a trouble (Non-trouble mode) 

 
Note: 
Vehicle 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. 

7D1-60  TRANSFER CONTROL SYSTEM 

Though the indicator responds when shifting from 4H to 2H(or other position), it returns 
to 4H. 

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 if the 
Check4WD lamp lights up. 
Is the Check4WD lamp OFF? 

Go to step 4. 

Failed actuator position detection 
(limit) switch (LS1, LS2, LS3, 
LS4, GND). 
Short or disconnection of harness 
of this detection switch. 
Refer to paragraph of 
Check4WD. 
After repairing, trace this chart 
from the beginning. 

4 

Press the 2H button. 
Is the sound of relay heard from 
the transfer controller? 

Go to step 5. 

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

5 

Is the sound of a running motor 
heart? 

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

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

If the motor does not or cannot run at all (stuck transfer mechanism, disconnected motor, failed drive circuit), the 
lamp blinks at 4Hz when the position is shifted to other position by pressing the button for more 10 seconds (20 
seconds in case of neutral position). 
 
 

TRANSFER CONTROL SYSTEM  7D1-61 

From 4H to 4L; Even after the correction step 3-3(*), 4Lo indicator blinks at 4Hz 

Step Action 

Yes 

No 

1 

Is the ignition switch ON? 

Turn it OFF once. 

Go to step 2. 

2 

Turn ON the ignition switch and 
check the valve.  Do not start 
the engine. 
Has the valve check for 2 
seconds been completed 
normally? 

Go to step 3. 

Refer to the paragraph about the 
indicator when it does not react 
when shifted from 2H to 4H. 
After taking the remedy, trace this 
chart from the beginning. 

3 

Shift to 2H. 
Can be shifted to 2H and then to 
4H? 

Go to step 4. 

Refer to the paragraph about 
shifting from 2H to 4H. 
In particular, check if not at the 
Check4WD condition, return to 
this chart and trace it from the 
beginning. 

4 

Set to N position in case of AT 
and set to the neutral position in 
case of MT and check if the 
lamp blinks at 4Hz after 
operation. 
 

Failed T/M position switch and 
harness (failure of TM1 and TM2 
harness and their related 
switches shown in the figure). 
Incorrect wiring. 
Repair as required and trace this 
chart from the beginning. 

Shift back to 4H and go to step 5.

5 

Start the engine and use the 
vehicle. 
Does the speedometer run at 
this time? 

Go to step 6. 

Failure of speed sensor or 
disconnection or short of harness 
(for the meter). 
After repairing, trace this chart 
from the beginning. 

6 

Check the harness between the 
transfer controller and speed 
sensor. 
(Check the engine rotation 
detection harness at the same 
time.) 
Is any trouble detected? 

Failed harness between the 
transfer controller and speed 
sensor. 
After repairing, trace this chart 
from the beginning. 
(Repair the engine rotation 
detection unit, if required.) 

Go to step 7. 

7 

Run the vehicle for several 
meters, stop it, meet the 
permission requirements for 
operation limits. 
Did you wait for several seconds 
after the requirements were 
met? 

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

You did not wait for enough time.  
Optimum waiting time is 1 second 
or maximum 3 minutes, 
depending on the previous 
conditions. 
Refer to the paragraph about 
operation without failure. 

 

*Before determining a trouble (Non-trouble mode)