2002 ISUZU AXIOM ECO mode

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±12
Indication During Transition of Shift Rod
When the TOD switch is turned, and the signals from the
AXLE switch do not comply with the signal conditions of
the 4H and 4L switch, the indicator lamp state selected on
the TOD switch and light-off mode are repeatedly output
at an interval of 1.0 second.NOTE: After the TOD switch is turned to the specified
position and the AXLE switch generates compliant
signals, the normal output status is returned.
C07R100010
Bulb Check
When the starter switch is turned on, the TOD indicator
lamps go 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 TOD
switch is in any position.
C07RW016

DRIVE LINE CONTROL SYSTEM (TOD) 4B2±16
How to Clear The Trouble Code
The trouble codes saved to the control unit can be deleted
by the following procedure if the starter switch is being in
the OFF position.
1. Short-circuit terminal 8 of the self-diagnostic
connector to GND (terminal 4 or 5).
2. Turn on the starter switch while maintaining the state
of step1, and stop short-circuiting terminal 8 to GND
within five seconds.
826R200011
3. If the conditions shown in steps 1 and 2 are met, the
trouble codes saved to the control unit are cleared.
(After the codes are completely deleted, the code 12
that indicates the normal condition is continuously
displayed.)
Precautions on Diagnosis
Replacement of Control Unit
The control unit itself rarely fails. In most cases, the
harnesses have failed (i.e. short-circuit) to cause
secondary troubles. Other cases include that the cause
has been unknown due to intermittent occurrence of
troubles and the troubles are removed accidentally along
with replacement of control unit, resulting in misjudgment
of cause. Therefore, before replacing the control unit,
check the connector joints and whether the unspecified
current flows in the control unit due to short-circuit
between harnesses.
Trouble Intermittently Observed
Troubles intermittently observed are mostly attributable
to temporary imperfect connection of harnesses and
connectors.
When such troubles are found, check the associated
circuit according to the following procedure.
1. Check whether improper connectors are plugged in
or connector terminals are completely engaged.
2. Check whether the terminals are deformed or
damaged. If yes, remove the deformation or damage
and connect the terminals securely.3. It is likely that wires in the harness are falsely broken.
Therefore, in examination of failed harness circuit,
shake the harness for check to such extent that the
harness will not be damaged.
Test Run of Failed TOD Vehicle
If the TOD indicator lamps experienced faulty operation
even once in the past, the failed portion can be identified
by use of the procedure ªDiagnosis from Trouble Codesº
or ªTrouble Diagnosis Depending on the Status of TOD
Indicatorº. If the troubles that are only recognized as
abnormal phenomena of the vehicle by the driver are
observed, conduct the test run in the following procedure
to reproduce the faulty phenomena and diagnose the fault
for each phenomenon.
1. Start the engine, and check that the TOD indicator
lamps are turned on for about two seconds for initial
check; the CHECK lamp goes off; and the TOD
indicator lamps display the specified drive mode. (If
the CHECK lamp starts blinking, read the trouble
codes and identify the failed portion.)
2. While keeping the vehicle standstill, operate the TOD
switch to change the modes: 2H mode"TOD
mode"4L mode"TOD mode"2H mode. Check
that the TOD indicator lamps correctly display the
status whenever the mode is changed. If the
transition status is displayed during the shift
operation, run the vehicle a little to complete shifting.
3. Slowly start the vehicle in the TOD mode, and add the
power to accelerate to at least 40 km/h (25 mph)and
maintain the speed for about two minutes. Apply the
brake to completely stop the vehicle. Repeat this test
pattern at least three times.
4. Turn the steering to the right end (or left end) in the
TOD mode, and slowly start the vehicle and make a
circle five times. Next, conduct the same test in the 2H
mode.
5. Slowly start the vehicle in the TOD mode, and
accelerate to at least 40 km/h (25 mph). Keep the
established speed, carefully change the mode in the
sequence ªTOD mode"2H mode "TOD modeº
while checking that the shift is complete in each mode
change. After the test, apply the brake to completely
stop the vehicle.
6. Slowly start the vehicle in the TOD mode, and
accelerate to at least 40 km/h (25 mph). Apply the
brake strongly so that the ABS works, and completely
stop the vehicle.
7. Slowly start the vehicle in the 4L mode, and
accelerate to at least 20 km/h (13 mph). Apply the
brake to completely stop the vehicle.
If the CHECK lamp starts blinking during the test run, read
the trouble codes and give appropriate maintenance
according to the diagnostic procedure. If the TOD
indicator lamps are lit abnormally during the run, check
the lighting condition and give appropriate maintenance
according to the diagnostic procedure. Even if the
phenomena are not observed, try to reproduce the
abnormal state reported by the customer to the possible
extent.

4B2±59
DRIVE LINE CONTROL SYSTEM (TOD)
Check flowTrouble codePhenomenonStandard
1233 (P1762)The ADC line is short-circuited to
GND.Ð
NOTE:

The on/off signal line of the shift on the fly system is
short±circuited to GND.

The system enters into the fail-safe mode because of
fusing or system protection.
(If a short±circuit is observed on GND, the output to
the on/off signal line becomes 0V.)
D04R200023

DRIVE LINE CONTROL SYSTEM (TOD) 4B2±88
StepActionYe sNo
11. Turn on the starter switch.
2. The car stops, the AT selector is the N position, and the brake
is applied.
When the TOD switch is changed to the TOD (or 2H) position, is
12V observed between terminals 44 and 47 (4L switch)?
Go to Step 2Go to Step 4
21. The car stops, the AT selector is the N position, and the brake
is applied.
When the TOD switch is changed to the 4L position, does the
transfer become the 4L state?
Go to Step 3
Refer to
ªDiagnosis from
symptomº.
3Is 0V observed between the terminal 44 and 47?The ECU has
failed.Replace
the ECU.
Go to
Step 10Go to Step 10
41. The car stops, the AT selector is the N position, and the brake
is applied.
When the TOD switch is changed to the TOD (or 2H) position, is
12V observed between the connector (C±37) terminal 22 and 25?
Go to Step 5Go to Step 6
51. Turn off the starter switch and connect the EUC connector.
2. The car stops, the AT selector is the N position, and the brake
is applied.
When the TOD switch is changed to the 4L position, is 0V
observed between terminals (C±37) 22 and (C±37) 25 (4L
switch)?The phenomenon
is not
reproduced.
Refer to
ªTrouble
intermittently
observedº.
Go to Step 6
61. Turn off the starter switch and connect ECU connector.
2. Turn on the starter switch.
3. The car stops, the AT selector is the N position, and the brake
is applied.
4. Change the TOD switch to the TOD (or 2H) position.
5. After the transfer has changed to the TOD (or 2H) mode, turn
off the starter switch and disconnect the ECU connector
(C±37).
Is there the continuity between the connector (C±37) terminal 22
and 25?
Go to Step 9Go to Step 7
71. Turn off the starter switch and connect the ECU connector.
2. Turn on the starter switch.
3. The car stops, the AT selector is the N position, and the brake
is applied.
4. Change the TOD switch to the 4L position.
5. After the transfer has changed to the 4L mode, turn off the
starter switch.
6. Disconnect the ECU connector.
Is there the continuity between the connector (C±37) terminal 22
and 25?
The phenomenon
is not
reproduced.
Refer to
ªTrouble
intermittently
observedº.
Go to Step 8
81. Turn off the starter switch and connect the ECU connector.
2. Turn on the starter switch.
3. The car stops, the AT selector is the N position, and the brake
is applied.
4. Change the TOD switch to the TOD (or 2H) position.
5. After the transfer has changed to the TOD (or 2H) mode, turn
off the starter switch.
6. Disconnect the transfer connector (A±1).
Is there the continuity between the connector terminal (A±1) 12
and GND?
Repair the
transfer.
Go to
Step 10
Repair the circuit
between (C±37)
22 and (A±1) 12.
Go to
Step 10

4B2±95
DRIVE LINE CONTROL SYSTEM (TOD)
StepActionYe sNo
1Start the engine.
When the TOD switch is selected to the TOD position, is 0V
observed between terminals 42 and 47?
Go to Step 2Go to Step 4
21. The car stops, the AT selector is N position, and the brake is
applied.
2. Select the TOD switch to the 4L position.
Is 0V observed between terminals 42 and 47?
Go to Step 3Go to Step 4
31. The car stops, the AT selector is N position, and the brake is
applied.
When the TOD switch is selected to the 4L position, is 12V
observed between the terminal 19 and 47?The phenomenon
is not
reproduced.
Refer to
ªTroubles
intermittently
observedº.
The ECU has
failed.Replace
the ECU.
Go to
Step 8
41. The car stops, the AT selector is N position, and the brake is
applied.
When the TOD switch is selected to the 2H position, is the battery
voltage observed between the terminal 23 and 47.
Go to Step 5Go to Step 7
5When the TOD switch is selected to the TOD position (TOD
mode), is 0 ~ 1V observed between terminals 23 and 47?
Go to Step 6Go to Step 7
61. The car stops, the AT selector is N position, and the brake is
applied.
When the TOD switch is selected to the 4L position, is 0V
observed between terminals 23 and 47?Repair the circuit
or check the
ªFront Axle
Disconnectº.
(Refer to
section
4B
)
Go to
Step 8Go to Step 7
7Is any of the trouble codes 28 (P1760), 32 (P1761) and 33
(P1762) recorded?Examine the
trouble based on
ªDiagnosis from
Trouble Codesº.The ECU has
failed. Replace
the ECU.
Go to
Step 8
8Check that all the parts are mounted.
Is this step complete?
Verify the repair.Go to Step 8

DRIVE LINE CONTROL SYSTEM (TOD) 4B2±102
Diagnosis from Symptom
Troubles that are not indicated by the warning lamp are
listed in the table below. These troubles are caused by the
faults that cannot be detected by the self-diagnostic
function of the control unit.
If this type of trouble is observed, interview the customer
and conduct test runs to reproduce the trouble,
cross-check the reported trouble with the listed
phenomena, and diagnose and analyze the trouble on the
item by item basis.
PhenomenaMajor causeCorrective action
1The tight corner braking is
observed when the vehicle is
subject to full steering.
The standard tires are not used.

The tire pressure is incorrect.

The tires are worn inuniformity.

The transfer or wiring is
imperfect.

The limited slip differential is
failed.Check and recondition the
vehicle according to Chart 1.
2Even if the TOD switch is selected
to the TOD position, the F4WD
mode is not active, resulting in
remarkable rear wheel spin.
The transfer or wiring is
imperfect.

The shift on the fly system is
failed.Check and recondition the
vehicle according to Chart 2.
3
When the TOD switch is
selected to the TOD position,
the drive resistance of the
F4WD system is too large to get
sufficient running speed.

Noised drive line.
The standard tires are not used.

The tires are worn inuniformity.

The transfer or wiring is
imperfect.

The limited slip differential is
failed. Check and recondition the
vehicle according to Chart 1.
4The shift on the fly system (front
axle disconnect) generates gear
noises.
The wiring is imperfect.

The shift on the fly system is
failed.Check and recondition the
vehicle according to Chart 3.
5The braking distance gets long
even when the ABS is active.
The wiring is imperfect.

The ABS is failed.Check and recondition the
vehicle according to Chart 4.
6The transfer does not change to the
low range from the high range.
The transfer or wiring is
imperfect.

The TOD switch is imperfect.

The AT inhibitor switch is
imperfect.
Check and recondition the
vehicle according to chart 5.
7The transfer does not change to the
high range from the low range.
im erfect.

The brake switch is imperfect.

The engine speed signal is
imperfect.

The speed sensor is imperfect.
Check and recondition the
vehicle according to chart 6.
8The transfer stays neutral and the
vehicle does not run.
The transfer is imperfect.Check and recondition the
vehicle according to chart 7.

DRIVE LINE CONTROL SYSTEM (TOD) 4B2±108
Chart 3The shift on the fly system generates gear noises.
(The fuel economy is bad in the 2H mode.)
Function of circuitÐ
Fail conditionWhen the vehicle is run in the 2H mode, the shift on the fly system generates gear
noises or the front wheel gears are engaged to generate a shock.
D04R200021