Isuzu KB P190. Manual — part 1230

7D1-46 TRANSFER CONTROL SYSTEM

Diagnosis

Before determining a trouble (Non-trouble mode)

1. When shifting from 2H to 4H:

1-1-1 When the flashing frequency of the 4WD indicator is changed from 2Hz to 4Hz (Shift on the fly)

If the load is too large to shift the gears synchronously, the operation is repeated up to 3 times. If the shifting
is not effected after being repeated 3 times, the indicator frequency is changed from 2Hz to 4Hz. At the same
time, the actuator condition is changed to 2H, indicator flashes at 4Hz for 10 seconds, and then goes out.
Cause of excessive synchronous shifting load
• Extremely low temperature (the oil viscosity of the front differential increases requiring a large load for

synchronization).

• High speed (since the difference of relative revolutions of gears to be shifted synchronously is too large,

required work load per unit time becomes larger).

Step 1-1-1:

Stop the vehicle or decrease the speed and operate as required again.

1-1-2 When the flashing frequency of the 4WD indicator is changed from 2Hz to 4Hz (Rigid and free wheel

Hub) / Block out of meshing spline in transfer case.

Step 1-1-2:

Run the vehicle forward and backward several meters and operate as required again.

1-2 When the flashing of 4WD indicator at 2Hz continues more than 11.5 seconds (repetition of 3 times of

above No.1 is counted) (Shift on the fly)

If there is difference of revolutions and phases between the front wheel and the axle, connecting the front
wheel and axle is difficult.
Until shifting in the transfer and connection of the front wheel and axle are completed

∗

, the indicator flashes at

a frequency of 2Hz. In the above case, the indicator continues flashing at a frequency of 2Hz until the
connection of the front axle is completed. (If the shifting in the transfer is not completed, the flashing
frequency is changed to 4Hz (above No.1).)
By correcting the difference of relative revolutions and deviation of phases, the shifting can be completed.

Step 1-2:

While the vehicle is running, check it is safe around the vehicle and then accelerate or decelerate the

vehicle while going straight.

When the vehicle is at a stop, run the vehicle forward and backward several meters.

2. When shifting from 4H to 2H

2-1 When 4WD indicator continues flashing at 2Hz

When shifting from 4H to 2H, the 4WD indicator continues flashing at 2Hz until separation in the transfer and

the separation of the front wheel axle are completed

∗

. When torsional torque is accumulated in the drive

system, separation in the transfer and separation of the front axle

∗

is difficult. In such a case, they can be

separated by removing the torsional torque of the drive system.

Step 2-1:

While the vehicle is running, check it is safe around the vehicle and then accelerate or decelerate the

vehicle while going straight.

When the vehicle is in stop, run the vehicle several meters forward and backward.

∗: Shift on the fly only.

TRANSFER CONTROL SYSTEM 7D1-47

3. Shifting from 4H to 4L

3-1 When the 4L indicator flashes at 2Hz

When shifting from 4H to 4L, the 4L indicator continues flashing at 2Hz until shifting in the transfer case is

completed. The phases of the engaged splines may sometimes deviate preventing completion of shifting. By

correcting the deviation of phases, shifting is completed.

Step 3-1:

(In case of AT):

Set the select bar of the transmission to the D position.

(In case of MT): Set the lever of the transmission to a position allowing running and engage the clutch

gently.

At this time, some rotating force acts on the engaged splines, phase is corrected and the engagement is

completed.

3-2 When the 4L indicator flashes at 2Hz for 10 seconds and then keeps ON again (AT vehicle)

This condition occurs when torsional torque has been generated between the transmission and road surface

and the transfer standby mechanism cannot absorb it completely.

Step 3-2:

Set the select lever of the transmission to the N position. (Stepping on the brake pedal is effective at

this time.)

3-3 When the 4L indicator flashes at a frequency of 4Hz

Shifting from 4H to 4L is restricted.

When the vehicle is running, the transmission lever is at the running range and the engine speed is high (L4:

3000rpm or more V6: 2000rpm), the transfer cannot be shifted from 4H to 4L (restriction on operation).

Restriction on operation (Except 4JA1-T)

The 4H, neutral and 4L shifting mechanism has no synchronization function. Therefore, if relative rotations in the
mechanism become excessive, shifting exerts adverse influence on the internal mechanism of the transfer. To
avoid such a trouble, vehicle condition is detected to restrict the operation (vehicle speed, engine speed and TM
position).

Requirement to restrict the speed: Vehicle should be in stop.

Due to the detection logic, time to wait for start of operation may be required.

A/T: If the vehicle is in stop for a long time at the TM running range (D, 1, 2) before operating the AT, waiting
time becomes longer (from 1 second to 3 minutes at the maximum).

M/T: If the vehicle is at stop with the clutch stepped on at the T/M running position (1 – R), the time to wait
becomes longer.

Waiting time means the time commencing from when other requirements (engine speed and T/M position) are
met to permission of the speed restriction. Operation during the waiting time is not permissible.

The waiting time is 1 second at the minimum and increases up to 5 seconds if the above condition continues for
3 minutes. After that, the waiting time increases up to 3 minutes in 2 minute intervals.

When it is clear that the above condition has continued and reduction of waiting time is required, turn on or off
the ignition or start and stop the vehicle several meters.

Requirements for permission of restriction on engine speed: Engine speed should be decreased.

The engine speed of 3000rpm (V6: 2000rpm) or below is advisable.

Requirements for permission of restriction on T/M position restriction:

(AT) N range is recommended

(MT) should be at the neutral.

These requirements for permission should all be met before the switch is operated. If the requirements are met
after operation, operation is not automatically effected but re-operation is required after permission is given.

7D1-48 TRANSFER CONTROL SYSTEM

Restriction on operation (4JA1-T)

The 4H, neutral and 4L shifting mechanism has no synchronization function. Therefore, if relative rotations in the
mechanism become excessive, shifting exerts adverse influence on the internal mechanism of the transfer. To
avoid such a trouble, vehicle condition is detected to restrict the operation (vehicle speed, and TM position).

Requirement to restrict the speed: Vehicle should be in stop.

Requirements for permission of restriction on engine speed: Engine speed should be decreased.

The engine speed of 3000rpm or below is advisable.

Requirements for permission of restriction on T/M position restriction:

should be at the neutral.

These requirements for permission should be all met before the switch is operated. If the requirements are met
after operation, operation is not automatically effected but re-operation is required after permission is given.

Note: Don’t’ accelerate engine speed a the time of this operation.

Step 3-3:

Stop the vehicle. (Close the accelerator and decrease the engine speed to below L4: 3000rpm, V6:

2000rpm.)

(In case of AT):

Set the transmission select lever to the N position.

(In case of MT): Set the transmission lever to the neutral position. (Stepping on the clutch is

recommended.) Push the 4L button.

If shifting operation is not completed (the lamp flashes at 2Hz), perform step 3-1.

4. Shifting from 4L to 4H

4-1 When 4L indicator continues flashing at 2Hz

When shifting from 4L to 4H, the 4L indicator continues flashing at 2Hz until the shifting in the transfer case is

completed. Phases of engaged splines may deviate and the operation may not be completed in some cases.

Shifting is completed by correcting the deviation of the splines.

Step 4-1: (same as step 3-1)

(In case of AT):

Set the transmission select lever to the D position.

(In case of MT):

Shift the transmission lever to a position allowing running and engage the clutch

gently.

4-2 When the indicator continues flashing at 2Hz for 10 seconds and then keeps on at 4L again (AT

vehicle)

This condition occurs when torsional torque has been generated between the transmission and the road

surface (use of the parking position on a slope). Resistance against the separation of the driving force cannot

be completed by the waiting mechanism of the transfer.

Shifting is also possible by using the brake at the neutral position of the transmission

Step 4-2: (Same procedure as the step 3-2)

Set the transmission select lever to the N position.

(Leaving the brake lever and stepping on it again is recommended.)

4-3 When the 4L indicator flashes at 4Hz

Shifting from 4L to 4H is restricted.

When the vehicle is running, the transmission lever is at the running range, and the engine speed is high, the

transfer 4L cannot be shifted to 4H.

TRANSFER CONTROL SYSTEM 7D1-49

Step 4-3: (Same procedure as the step 3-3)

Stop the vehicle (close the accelerator and decrease the engine speed to L4: 3000rpm V6: 2000rpm or

below).

(In case of AT):

Set the transmission select lever to the N position.

(In case of MT):

Set the transmission lever to the neutral position (stepping on the clutch lever is

recommended).

Push the 4H button.

If shifting is not complete (indicator flashes at 2Hz), go to step 4-1.

5. When shifting from 4H or 4L to neutral

(Same procedure is required when shifting from 2H but in such a case, requirements for shifting from

2H to 4H are also applied.)

5-1 Neutral indicator continues flashing at 2Hz

The neutral indicator continues flashing at 2Hz until 4H (4L) is completely separated in the transfer. If torsional

torque has accumulated between the transmission and road surface, separation may be difficult.

Step 5-1:

If the operation is not complete, execute step 7 for confirmation.

(In case of AT):

Set the transmission select lever to the D position.
After confirming that the gears are at the neutral position, return the lever to the N
position.

(In case of MT):

Set the transmission lever to a vehicle running position and engage the clutch gently.
After confirming that the gears are at the neutral position, return the lever to the
neutral position

5-2 When the neutral indicator flashes at 4Hz

As in the case of shifting from 4L to 4H, restriction is imposed to the operation from 4L or 4H (including 2H). If

the transmission lever is at a running range and engine speed is high (L4: 3000rpm, V6: 2000rpm or more)

while the vehicle is running, operation from the 4L or 4H (including 2H) of the transfer to the neutral is

impossible (restriction on operation).

Step 5-2:

Stop the vehicle.

(In case of AT):

Set the transmission select lever to the N (or P) position.

(In case of MT):

Set the transmission lever to the neutral position (at this time, stepping on the clutch
is recommended).

Keep pushing the 2H and 4L button for 10 seconds.

Follow the start procedure for confirmation. (Confirmation of drive force is not transferred; same as in
step 5-1)

After the confirmation, set the transmission to the neutral position in the case of MT or to the neutral
position in the case of AT.