2002 ISUZU AXIOM wheel

4B1±2
DRIVELINE CONTROL SYSTEM
Shift On The Fly System
Outline of Shift on The Fly System
The shift on the fly system switches between 2 wheel
drive (2WD) and 4 wheel drive (4WD) electronically by the
driver turning the TOD switch on the instrument panel.
This system will control the following operations. (Shifting
between ª4Hº and ª4Lº must be performed by TOD
switch.)
1. Transmitting the torque to the front propeller shaft.
2. Connecting front wheels to, and disconnecting them
from, the front axles by axle motor actuator.
3. Indicating on instrument panel.
4. 4WD out signal to other Electronic Brake Control
Module (EBCM).
System Diagrams
412R200008

4B1±3
DRIVELINE CONTROL SYSTEM
Normal Operation
The axle disconnect controller is driven by the signal from
TOD control unit and the axle motor actuator connects (or
disconnects when the 4WD switch is deactivated) the
front wheels to the front axles.
Time Chart of Shifting Under Normal Condition
F04R200002
4WD out signal to other Electronic Brake Control
Module : TOD Control Unit of shift on the fly sends 4WD
out signal to other Electronic Brake Control Module as
below.
4WD out signal
(Period)
Vehicle ConditionTransfer position switchFront axle switch
120 ms2WD2WD (Open)2WD (Open)
240 ms4WD4WD (Close)4WD (Close)

4B1±4
DRIVELINE CONTROL SYSTEM
Functions of Indicator Lamp
TOD Switch and Indication of Drive Mode
The TOD switch sends signals to the TOD control unit
which selects drive modes and controls the shift on the fly
system (axle disconnect : ADC).
TOD
switch
tt
Drive modeTransfer shift conditionTransfer posi-
tion detectionShift on the flyTOD indicator
state
state4HSW4LSWAxle
SWADC circuit
2HRear-wheel
drive (RWD)Permissible during
driving (less than
100 km/h or 62 mph)OFFOFFOFFTurning on
electricity
TODElectronic
torque split
4WD (HIGH)
OFFOFFONTurning off
electricity
4WD (HIGH)
(TOD)AT: Neutral
Brake: Applied
Th t (l4LLow range
mechanical
direct 4WD
(LOW) (4L)The car stops (less
than 2 km/h or
1.2 mph and less than
1500 rpm)OFFONONTurning off
electricity
ADC: Shift on the fly
SW: Switch
Bulb check :The bulb of indicator lamp is checked for 2
seconds when ignition key is turned on.
Bulb Check
When the starter switch is turned on, the TOD indicator
lamps comes on as shown below.
NOTE: Once the starter switch is turned on, all the TOD
indicator lamps are lit for two seconds even if the transfer
lever is in any position.
C07RW016

DRIVE LINE CONTROL SYSTEM (TOD) 4B2±2
General Description
412R200008
TOD (Torque on Demand) system is traction state control
system to vehicle.
Transfer Position and Drive Mode
Three drive modes can be selected through operation of
TOD switch and transfer lever.
Transfer Position
TOD SWITCHModeDrive mode
HIGH2HRWDRear wheel drive
TOD4WD
(HIGH)Electronically controlled torque split
four wheel drive
LOW4L4WD
(LOW)Low-speed mechanical lock-up four
wheel drive
The electronic control unit (ECU) judges the signals from
the TOD switch and controls the transfer drive mode and
shift-on-the-fly system status.

4B2±3
DRIVE LINE CONTROL SYSTEM (TOD)
TOD Control
The TOD position usually drives the rear wheels, and
transmits the torque to the front wheels with the help of
electronically controlled torque split mechanism
according to running conditions encountered. The driving
force is directly transmitted to the rear wheels. This force
is split by the transfer and delivered to the front wheels.
The magnitude of the torque transmitted to the front
wheels is controlled by changing the pressing force of the
multi plate disk clutch built in the transfer unit. The
pressing force of the clutch is controlled by changing the
duty ratio to the electromagnetic coil mounted to the rear
of the clutch. When the clutch is completely disengaged,
the rear wheels are driven. When the clutch is completely
engaged, a rigid four wheel drive mode is obtained. The
torque split status is controlled continuously between the
rear wheel and four wheel drive modes. This system
includes front and rear speed sensors, and receives
throttle position sensor and engine speed information
from the PCM, ABS control unit signal, brake switch
signal, and shift motor position information.
The control unit receives signals sent from these sensors
and changes the pressing force of the multi-plate disk
clutch to determine the torque distribution on the front and
rear wheels. Therefore, when the slip of the rear wheels is
increased against the current torque level in the normal
rear wheel drive mode, the control unit detects the slip
condition, determines the optimum torque based on the
feedback control logic, and increases the torque to the
front wheels.
The control unit uses the signal from the throttle position
sensor to predict the future vehicle condition and the
intention of the driver with respect to acceleration and
deceleration, and determines the initial torque distribution
using these data and the information from the speed
sensors.
In case of small circle turning in the parking lot, for
example, the control unit minimizes the clutch pressing
force to restrict a braking phenomenon. When the ABS
becomes active, the control unit optimizes the clutch
pressing force to ensure stable braking.
TOD Indicator Control
The TOD indicator on the instrument panel informs the
driver of the current working status of the transfer unit.
The information is the drive mode (2H, TOD, 4L,
transition). The indicator can display occasional errors
and corresponding error codes.
Abbreviations
ABS Anti-lock Brake System
ADC Axle Disconnect
(Shift on the fly system)
VB Battery Voltage
VIGN Ignition Voltage

4B2±9
DRIVE LINE CONTROL SYSTEM (TOD)
High-Low Shift Motor
F07R200002
Legend
(1) Reduction Hub
(2) Mechanical Lock Sleeve (Including the built-in
Spring)
(3) Lockup Shift Fork
(4) Return Spring
(5) To TOD Control Unit
(6) Fixed Contact Point
(7) Encoder
(8) Worm gear
(9) Rotate
(10) Shift Motor
(11) The shift cam (12) can be turned freely around
the shift shaft (14).(12) Shift Cam
(13) Torsional Spring
(14) Shift Shaft
(15) Shift Rod
(16) High-Low Shift Fork
(17) High
(18) Low
(19) 2H and TOD Position
(20) Direct Four Wheel Drive (4L Position)
(21) Earth
(22) High
(23) Low
(24) High
(25) Low
When the TOD switch is changed to the 4L (or TOD)
position from the TOD (or 4L) position, the TOD control
unit drives the high±low shift motor according to the
signal. The transfer is shifted to low range from high range
(or to high range from low range) by the shift motor.
The high-low shift motor can run, only when the operation
meets the following conditions to prevent an unexpected
shift between high and low range by a operation error.
1. The car stops. (less than 2 km/h or 1.2 mph and less
than 1500 rpm.)2. The AT selector position is neutral.
3. The brake is applied. (brake switch is on.)
The shift motor has a built-in encoder which watches
motor rotation position. The control unit controls the
rotation of the shift motor based on the position code
detected by the encoder.
The encoder position plate turns together with the shift
shaft and switches on or off the current from the 4 (four)
fixed contact points on the case, then the control unit
recognizes the rotation position of the shift motor.

4B2±11
DRIVE LINE CONTROL SYSTEM (TOD)
Functions of TOD Switch and
Indicator Lamp
TOD Switch and Indication of Drive Mode
The TOD switch sends signals to the TOD control unit
which selects drive modes and controls the shift on the fly
system (axle disconnect : ADC).
TOD
switch
state
Drive modeTransfer shift conditionTransfer
position
detectionShift on the flyTOD indicator
state
4HSW4LSWAxle
SWADC circuit
2HRear-wheel
drive (RWD)Permissible during
driving (less than
100 km/h or 62 mph)OFFOFFOFFTurning on
electricity
TODElectronic
torque split
4WD (TOD)OFFOFFONTurning off
electricity
AT: Neutral
Brake: Applied
The car stops4LLow range
mechanical
direct 4WD
(4L)The car sto s
(less than 2 km/h or
1.2 mph and less than
1500 rpm)OFFONONTurning off
electricity
ADC: Shift on the fly
SW: Switch
TOD
Switch
TOD control unit terminal No.TOD indicator
stateSwitch
stateTOD indicatorTOD switchstate
state
7(Front)8(Rear)19(Auto)30(2H)43(4L)
2HOFFONOFFONOFF
TODONONONOFFOFF
4LONONOFFOFFON

DRIVE LINE CONTROL SYSTEM (TOD) 4B2±42
StepActionYe sNo
11. Connect TECH 2.
While running in TOD mode, does TECH±2's front speed sensor
indication change with vehicle speed?
Go to Step 2
Repair and
inspection front
speed sensor
tone wheel.
Go to
Step 6
21. Clear the trouble code.
While running at 40 km/h or 25 mph in TOD mode for 30
consecutive sec, is the trouble code reissued?
Go to Step 3
The trouble is not
reproduced.
Refer to
ªTroubles
intermittently
observedº.
31. Turn off the starter switch.
2. Disconnect the ECU connector (C±38) and (C±37).
Is there the continuity between the connector (C±37) terminal 10
and 25?
Repair the circuit.
Go to
Step 6Go to Step 4
41. Disconnect the transfer connector (A±1).
Is there the continuity between the connector (C±37) terminal 10
and the connector (A±1) terminal 6, the connector (C±38) terminal
12 and connector (A±1) terminal 2, and the connector (C±38)
terminal 13 and connector (A±1) terminal 10?
Replace the front
speed sensor.
Go to
Step 5
Repair the circuit.
Go to
Step 5
51. Clear the trouble code.
While running at 40 km/h or 25 mph in TOD mode for 30
consecutive sec, is the trouble code reissued?
Replace ECU.
Go to
Step 6Go to Step 6
61. Check that all the parts are mounted.
2. Clear the trouble code.
Is this step complete?
Repeat the
ªDiagnosis Flowº.
Return to Step 6