ISUZU AXIOM 2002 Service Repair Manual

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

DRIVE LINE CONTROL SYSTEM (TOD) 4B2±4
System Components
Parts Location
A04R200004
Legend
(1) Mechanical Lock Sleeve
(2) Drive Chain
(3) Clutch Pack
(4) Electromagnetic Clutch Solenoid
(5) Output Shaft
(6) Rear Output Coupling
(7) Rear Speed Sensor
(8) Drive Sprocket
(9) Spring
(10) Return Spring
(11) Lockup Shift Fork
(12) Front Speed Sensor
(13) High-Low Shift Motor
(14) Driven Sprocket(15) Shift Shaft
(16) Front Output Coupling
(17) Front Output Shaft
(18) Shift Cam
(19) Torsional Spring
(20) High-Low Shift Fork
(21) Shift Rod
(22) Input Shaft
(23) Reduction Hub
(24) High-Low Planetary Gear
(25) High Position
(26) Low Position
(27) Oil Pump
(28) Free Position
(29) Lock Position

4B2±5
DRIVE LINE CONTROL SYSTEM (TOD)
Front and Rear Speed Sensors
The sensors are built in the transfer case, and detect the
rotation of rotors directly coupled to the propeller shafts.
Thirty rectangular pulses are output per one rotation of
the propeller shaft.
261RW045
Electromagnetic Coil
Receives the duty signals from the TOD control unit and
controls the pressing force of the clutch pressure cam.
261RW044
Multi Plate Disk Clutch Pack
Transmits the torque determined by the clutch pressing
force to the front propeller shaft via the front drive chain.
262RW029
Mechanical Lock Sleeve
Couples the front and rear propeller shaft mechanically
when the transfer shaft is in the 4L position.
262RW028

DRIVE LINE CONTROL SYSTEM (TOD) 4B2±6
High-Low Planetary Gear Set
Establishes an auxiliary transmission mechanism. When
the TOD switch is set to the 2H or TOD position, the
reduction gear ratio is 1.000 and the corresponding
driving force is generated. When the TOD switch is set to
the 4L position, the reduction gear ratio is 2.480 and the
corresponding driving force is generated.
262RW030
4H and 4L Switch
Detects the shift position of the transfer from the
movement of the shift rod and outputs signals to the TOD
control unit.
261RW002
Transfer Connector (12-pin type)
Transmits the input and output signals of the speed
sensors, electromagnetic coil, and 4H and 4L switche to
the vehicle harness. A waterproof 12-pin type is used.
261RW046
Transfer Connector (8-pin type)
Transmits the output signals of the shift motor position to
the vehicle harness and power for the shift motor to the
transfer. A waterproof 8-pin type is used.
261RY00039

4B2±7
DRIVE LINE CONTROL SYSTEM (TOD)
TOD Indicator Lamps (on the instrument
panel)
Inform the following items.

Bulb check

Drive mode

ABS IN status

BRAKE ON status
821R200016
Check Lamp
Inform the following items.

Bulb check

Fail (fail alarm)

Trouble code
821R200016

DRIVE LINE CONTROL SYSTEM (TOD) 4B2±8
TOD ECU
This control unit is mounted to the clutch pedal position
via a special bracket.
826R200019
Legend
(1) Brake Pedal Bracket

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.

DRIVE LINE CONTROL SYSTEM (TOD) 4B2±10
Motor Position and Encoder Position Code
High-Low Shift Motor PositionHigh-Low shift Motor Encoder SignalState of
MotorPosition aPosition bPosition cPosition dMotor
High EndAOFFOFFOFFONHigh Position
Near High EndBOFFONOFFON
High PositionCONONOFFON
Middle Zone (1)DONONONON
Middle Zone (2)EOFFONONON
Neutral PositionFOFFONONOFF
Middle Zone (3)GONONONOFF
Low PositionHONOFFONOFFLow Position
Low EndIONOFFONON
Encode Position Plate
F04R100005
Legend
(1) OFF Aria
(2) ON Aria(3) Low
(4) High
(5) Earth
Shift High Range and Low Range
When the car is stops (less than 2km/h or 1.2 mph and
less than 1500 rpm), the AT selector position is neutral,
the brake is applied, and the TOD switch is changed to 4L
from TOD (or to TOD from 4L), the high-low shift motor
starts by power applied from the TOD control unit and
turns the shift shaft through the worm gear.
The shift shaft turns the shift cam through the torsional
spring.
The end of the shift cam moves the lockup shift fork and
the spiral groove on the outside of the shift cam slides the
high±low shift fork.

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