ISUZU AXIOM 2002 Service Repair Manual

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.

4B2±103
DRIVE LINE CONTROL SYSTEM (TOD)
Chart 1The tight corner braking is observed.
Function of circuitÐ
Fail conditionWhen the vehicle is subject to full steering in the TOD mode, the drive resistance gets
large or the judder occurs. Otherwise, the above phenomenon is observed only when the
brake is applied.
D04R200021

DRIVE LINE CONTROL SYSTEM (TOD) 4B2±104
StepActionYe sNo
1Are the front and rear tires in specified size?
Go to Step 2
Replace the tires
with specified
ones, and service
the new tires.
Go to
Step 16
2Is the tire pressure correct?
Go to Step 3
Inflate the tires
with specified
pressure.
Go to
Step 16
3Are the tires free from abnormal wear?
Go to Step 4
Replace the tires
with specified
ones, and service
the new tires.
Go to
Step 16
4Are different types of tires used?
Go to Step 5
Replace the tires
with specified
ones, and service
the new tires.
Go to
Step 16
51. Start the engine.
2. Select the TOD switch to the TOD position.
3. Fully turn the steering to the left (or right) end, and select the D
range and start the creep run.
Does the tight corner braking occur? Is the judder with chug-chug
sound observed? * Use caution on the operation.
Go to Step 6 Go to Step 11
61. Select the TOD switch to the 2H position.
2. Fully turn the steering to the left (or right) end, and select the D
range and start the creep run.
Does the tight corner braking occur? Is the judder with chug-chug
sound observed? * Use caution on the operation.
Go to Step 7 Go to Step 14
7Is an LSD mounted to the rear differential? Go to Step 8 Go to Step 9
8Is the genuine LSD oil used in the rear differential?
Go to Step 9
Replace the
differential oil.
Go to
Step 16
9Does the engine output the power correctly?
Go to Step 10
Check the
engine.
Go to
Step 16
10Do the speed sensors work correctly? (Check trouble codes.)The ECU has
failed. Replace
the ECU.
Go to
Step 16
Replace the
speed sensors.
Go to
Step 16
11Is the tight corner braking observed only when the brake is
applied?
Go to Step 12
Conduct full
steering under
WOT.
Go to
Step 5
121. Turn on the starter switch.
Is 8 ~ 10 V observed between terminals 33 and 47?
Go to Step 13
Repair the circuit
of the ECU
connector
terminal 33 (ABS
IN).
Go to
Step 16

4B2±105
DRIVE LINE CONTROL SYSTEM (TOD)
StepNo Ye s Action
131. Apply the brake and fully turn the steering to the left (or right)
end, and start the creep run.
Does the voltage between terminals 11 and 22 range between 0.1
and 1.0V?Repair the
transfer
assembly.
Go to
Step 16
The ECU has
failed. Replace
the ECU.
Go to
Step 16
141. Select the TOD switch to the TOD position.
2. Fully turn the steering to the left (or right) end, and select the D
range and start the creep run.
Does the voltage between terminals 11 and 22 range between 0.1
and 1.0V?
Go to Step 15 Go to Step 10
151. Select the TOD switch to the 2H position.
2. Jack up the right front wheel.
Does the front tire rotate smoothly?The phenomenon
is not
reproduced.
Refer to
ªTroubles
intermittently
observedº
.
Repair the
transfer
assembly.
Go to
Step 16
16Check that all the parts are mounted.
Is this step complete?
Verify the repairGo to Step 16
*NOTE: Before checking this item, run the vehicle more
than 10 meters with the steering wheel in straight position
so that the 4L mechanical lock sleeve can be released
certainly.

DRIVE LINE CONTROL SYSTEM (TOD) 4B2±106
Chart 2The TOD mode is not active.
Function of circuitÐ
Fail conditionThe rear wheels spin in the TOD mode, so the driving torque is not transmitted to the
front wheels. The indicator lamps will not show the 4L and TOD status.
D04R200021

4B2±107
DRIVE LINE CONTROL SYSTEM (TOD)
StepActionYe sNo
1Is the trouble code 31(P1721) recorded?Examine the
trouble based on
ªDiagnosis from
Trouble Codesº.
Go to Step 2
2Is any of the trouble codes 28(P1760), 32(P1761) and 33(P1762)
recorded?Examine the
trouble based on
ªDiagnosis from
Trouble Codesº.
Go to Step 3
3When the TOD switch is selected to the specified position, do the
TOD indicator lamps show the correct status?
Go to Step 4
Examine the
trouble based on
ªTrouble
Diagnosis
Depending on
The Status of
TOD Indicatorº.
4Select the TOD switch to the 4L position, fully turn the steering to
the left (or right) end, and start the creep run. Does the tight corner
braking occur?
Go to Step 5
Repair the
transfer
assembly.
Go to
Step 7
51. Select the TOD switch to the TOD position.
2. Turn on the starter switch.
Does the voltage between terminals 11 and 22 indicate at least 3V
while the throttle is completely open?
Go to Step 6
The ECU has
failed. Replace
the ECU.
Go to
Step 7
6Does the voltage between terminals 11 and 22 indicate at least
0.1V while the throttle is completely closed?The TOD clutch
is worn. Repair
the transfer
assembly.
Go to
Step 7
The ECU has
failed. Replace
the ECU.
Go to
Step 7
7Check that all the parts are mounted.
Is this step complete?
Verify the repair.Go to Step 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

4B2±109
DRIVE LINE CONTROL SYSTEM (TOD)
StepActionYe sNo
1Do the indicator lamps show the correct status?
Go to Step 2
Examine the
trouble based on
ªTrouble
Diagnosis
Depending on the
Status of TOD
Indicatorº.
2Is any of the trouble codes 28(P1760), 32(P1761) and 33(P1762)
recorded?Examine the
trouble based on
ªDiagnosis from
Trouble Codesº.
Go to Step 3
3Turn on the starter switch.
Is the battery voltage observed between terminals 14 and 47?
Go to Step 4Go to Step 5
4When the TOD Switch is selected to the 2H position, are the front
axle gears correctly disengaged (and when the left front tire is
jacked up and turned, is the front propeller shaft standstill)?The phenomenon
is not
reproduced.
Refer to
ªTrouble
intermittently
observedº
.
The shift on the
fly system is
failed (refer to
Section 4B1 and
4C
).
5Does the battery voltage maintain the correct level?
Repair the battery
circuit.
Go to
Step 6
Repair the battery
and charging
system.
Go to
Step 6
6Check that all the parts are mounted.
Is this step complete?
Verify the repair.Go to Step 6

DRIVE LINE CONTROL SYSTEM (TOD) 4B2±110
Chart 4The braking distance gets long even when the ABS is active.
Function of circuitÐ
Fail conditionEnough deceleration is not obtained and the braking distance gets long even when the
ABS is active in the 2H mode.
D04R200021

DRIVE LINE CONTROL SYSTEM (TOD) 4B2–111
Step Action Yes No
1 Are the brake and ABS systems healthy?
Go to
Step 2
Repair the brake
and ABS. (Refer to
section 5A and 5B)
2 Turn on the star ter switch.
Is the battery voltage observed between terminals 14 and 47?
Go to
Step 3
Repair the
battery system.
Go to
Step 5
3 1. Select the TOD switch to the 2H position.
Does the voltage between terminals 36 and 47 range between
7.5 and 16V (0.12 seconds make a cycle)? Go to
Step 4
The ECU has
failed. Replace
the ECU.
Go to
Step 5
4 1. Turn off the starter switch.
2. Disconnect the connector (C–37).
Is there the continuity between the connector terminal (C–37) 14
and (C–6) 8?The
phenomenon is
not reproduced.
Refer to
“Trouble
intermittently
observed".
Repair the
harness.
Go to Step 5
5 Check that all the par ts are mounted.
Is this step complete? Verify the repair. Go to
Step 5