2002 ISUZU AXIOM low oil pressure

POWER±ASSISTED STEERING SYSTEM2A±9
The hydraulic pump is vane-type design. The submerged
pump has housing and internal parts that are inside the
reservoir and operate submerged in oil. There are two
bore openings at the rear of the pump housing. The larger
opening contains the cam ring, pressure plate, thrust
plate, rotor and vane assembly, and end plate. The
smaller opening contains the pressure line union, flow
control valve and spring.
The flow control orifice is part of the pressure line union.
The pressure relief valve inside the flow control valve
limits the pump pressure.Pressure Switch
When hydraulic pressure reaches 3430 kPa (500 psi), the
pressure switch of the power steering pump closes
causing the Powertrain Control Module (PCM) to actuate
the throttle valve, which increases the engine rpm to
prevent the overload-induced engine speed slow down.
The switch opens when hydraulic pressure drops to 2940
kPa (430 psi).
Steering Column
431RY00009
WARNING: T O AV O I D D E P L O Y M E N T W H E N
TROUBLE-SHOOTING THE SRS SYSTEM, DO NOT
USE ELECTRICAL TEST EQUIPMENT, SUCH AS
BATTERY-POWERED OR A/C-POWERED
VOLT-METER, OHMMETER, ETC., OR ANY TYPE OF
ELECTRICAL EQUIPMENT OTHER THAN
SPECIFIED IN THIS MANUAL. DO NOT USE A
NON-POWERED PROBE-TYPE TESTER.INSTRUCTION IN THIS MANUAL MUST BE
FOLLOWED CAREFULLY, OTHERWISE PERSONAL
INJURY MAY RESULT.
When servicing a vehicle equipped with Supplemental
Restraint System, pay close attention to all WARNINGS
and CAUTIONS.
For detailed explanation about SRS, refer to
Restraints
section.

2A±10
POWER±ASSISTED STEERING SYSTEM
The steering column has three important features in
addition to the steering function:
1. The column is energy absorbing, designed to
compress in a front-end collision to minimize the
possibility of injury to the driver of the vehicle.
2. The ignition switch and lock are mounted
conveniently on the column.
3. With the column mounted lock, the ignition and
steering operation can be locked to prevent theft of
the vehicle.The column can be disassembled and reassembled.
However, to insure the energy absorbing action, use only
the specified screws, bolts and nuts as designated, and
tighten them to the specified torque.
Handle the column with care when it is removed from the
vehicle. A sharp blow on the end of steering shaft or shift
lever, or dropping the assembly could shear or loosen the
fasteners that maintain column rigidity.
Power Steering System Test
Test Procedure
C02RW001
Legend
(1) Fluid Reservoir(2) Power Steering Unit
(3) Power Steering Pump
Test of fluid pressure in the power steering system is
performed to determine whether or not the oil pump and
power steering unit are functioning normally.
The power steering system test is used to identify and
isolate hydraulic circuit difficulties. Prior to performing
this test, the following inspections and corrections, if
necessary, must be made.

Inspect pump reservoir for proper fluid level.

Inspect pump belt for proper tension.

Inspect pump driver pulley condition. 1. Place a container under the pump to catch the fluid
when disconnecting or connecting the hoses.
2. With the engine NOT running, disconnect the
pressure hose at the power steering pump and install
power steering tester J-29877-A. The gage must be
between the shutoff valve and pump. Open the
shutoff valve.
3. Check the fluid level. Fill the reservoir with power
steering fluid, to the ªFullº mark. Start the engine,
then turn the steering wheel and momentarily hold it
against a stop (right or left). Turn the engine off and
check the connections at tester for leakage.

POWER±ASSISTED STEERING SYSTEM2A±11
4. Bleed the system. Refer to Bleeding the Power
Steering System
in this section.
5. Start the engine and check the fluid level. Add power
steering fluid if required. When the engine is at
normal operating temperature, increase engine
speed to 1500 rpm.
CAUTION: Do not leave shutoff valve fully closed
for more than 5 seconds, as the pump could become
damaged internally.
6. Fully close the shutoff valve. Record the highest
pressures.

If the pressure recorded is within 9300±9800 kPa
(1350±1420 psi), the pump is functioning within its
specifications.

If the pressure recorded is higher than 9800 kPa
(1420 psi), the valve in the pump is defective.

If the pressure recorded is lower than 9300 kPa
(1350 psi), the valve or the rotating group in the
pump is defective.
7. If the pump pressures are within specifications, leave
the valve open and turn (or have someone else turn)
the steering wheel fully in both directions. Record the
highest pressures and compare with the maximum
pump pressure recorded in step 6. If this pressure
cannot be built in either side of the power steering
unit, the power steering unit is leaking internally and
must be replaced.
8. Shut the engine off, remove the testing gauge.
9. Reconnect the pressure hose, check the fluid level
and make the needed repairs.
10. If the problem still exists, the steering and front
suspension must be thoroughly examined.
Maintenance
The hydraulic system should be kept clean and fluid level
in the reservoir should be checked at regular intervals and
fluid added when required. Refer to
Recommended
Fluids and Lubricants in General Information
section for
the type of fluid to be used and the intervals for filling.
If the system contains some dirt, flush it as described in
this section. If it is exceptionally dirty, the pump must be
completely disassembled before further usage. (The
steering unit cannot be disassembled.)
All tubes, hoses, and fittings should be inspected for
leakage at regular intervals. Fittings must be tight. Make
sure the clips, clamps and supporting tubes and hoses
are in place and properly secured.
Power steering hoses and lines must not be twisted,
kinked or tightly bent. Air in the system will cause spongy
action and noisy operation. When a hose is disconnected
or when fluid is lost, for any reason, the system must be
bled after refilling. Refer to
Bleeding the Power Steering
System
in this section.

Inspect belt for tightness.

Inspect pulley for looseness or damage. The pulley
should not wobble with the engine running.

Inspect hoses so they are not touching any other
parts of the vehicle.

Inspect fluid level and fill to the proper level.
Fluid Level
1. Run the engine until the power steering fluid reaches
normal operating temperature, about 55
C (130
F),
then shut the engine off.
2. Check the level of fluid in the reservoir.
3. If the fluid level is low, add power steering fluid as
specified in General Information to the proper level
and install the receiver cap.
4. When checking the fluid level after the steering
system has been serviced, air must be bled from the
system. Refer to
Bleeding the Power Steering
System
in this section.
Bleeding The Power Steering System
When a power steering pump or unit has been installed,
or an oil line has been disconnected, the air that has
entered the system must be bled out before the vehicle is
operated. If air is allowed to remain in the power steering
fluid system, noisy and unsatisfactory operation of the
system may result.
Bleeding Procedure
When bleeding the system, and any time fluid is added to
the power steering system, be sure to use only power
steering fluid as specified in General Information.
1. Fill the pump fluid reservoir to the proper level and let
the fluid settle for at least two minutes.
2. Start the engine and let it run for a few seconds. Do
not turn the steering wheel. Then turn the engine off.
3. Add fluid if necessary.
4. Repeat the above procedure until the fluid level
remains constant after running the engine.
5. Raise and support the front end of the vehicle so that
the wheels are off the ground.
6. Start the engine. Slowly turn the steering wheel right
and left, lightly contacting the wheel stops.
7. Add power steering fluid if necessary.
8. Lower the vehicle, set the steering wheel at the
straight forward position after turning it to its full steer
positions 2 or 3 times, and stop the engine.
9. Check the fluid level and refill as required.
10. If the fluid is extremely foamy, allow the vehicle to set
a few minutes, then repeat the above procedure.
Flushing The Power Steering System
1. Raise and support the front end of the vehicle off the
ground until the wheels are free to turn.
2. Remove the fluid return line at the pump inlet
connector and plug the connector port on the pump.
Position the line toward a large container to catch the
draining fluid.
3. While running the engine at idle, fill the reservoir with
new power steering fluid. Turn the steering wheel in
both directions. Do not contact or hold the steering
wheel to the wheel stops. This will cause the pump to
go to pressure relief mode, which may cause a
sudden fluid overflow at the reservoir.

POWER±ASSISTED STEERING SYSTEM2A±25
Inspection and Repair
Make all necessary adjustments, repairs, and part
replacements if wear, damage, or other problems are
discovered during inspection.
Rotor
442RS002Check that the groove in the vane is free from excessive
wear and that the vane slides smoothly. When part
replacement becomes necessary, the pump cartridge
should be replaced as a subassembly.
Vane
442RS003
Sliding faces of the vane should be free from wear.
(Particularly the curved face at the tip that contact with the
cam should be free from wear and distortion). When part
replacement becomes necessary, the pump cartridge
should be replaced as a subassembly.
Cam
The inner face of the arm should have a uniform contact
pattern without a sign of step wear. When part
replacement becomes necessary, the pump cartridge
should be replaced as a subassembly.
Side Plate
The sliding faces of parts must be free from step wear
(more than 0.01 mm), which can be felt by the finger nail.
The parts with minor scores may be reused after lapping
the face.
Relief Valve
The sliding face of the valve must be free from burrs and
damage. The parts with minor scores may be reused after
smoothing with emery cloth (#800 or finer).
Shaft
Oil seal sliding faces must be free from a step wear which
can be felt by the finger nail. Bushing fitting face must be
free from damage and wear.
O-ring, Oil Seal, Snap Ring
Be sure to discard used parts, and always use new parts
for installation. Prior to installation, lubricate all seals and
rings with power steering fluid.
Pressure Switch
Check the switch operation as follows:
With engine idling and A/C on, turn the steering wheel
fully to the left; compressor should interrupt and engine
idle speed will increase. Shut off A/C and again turn
steering fully to the left; engine idle will increase. If system
fails to function properly, disconnect connector at the
pressure switch and repeat system check while testing
continuity across disconnected SW connector.
Reassembly
1. Install oil seal to front housing. Be sure to discard
used oil seal, and always use new parts for
installation.
CAUTION: When installing the oil seal, be careful
not to damage the oil seal contacting surface of the
housing.
2. Install shaft assembly.

4A2±16DIFFERNTIAL (REAR)
16. Remove exciter ring.

Remove the exciter ring from the differential using a
mallet or a brass hammer if it is required.
NOTE: Discard the exciter ring after removal.
425RS097
Cleaning
Do not steam clean drive parts which have ground and
polished surfaces such as gears, bearings, and shafts.
These parts should be cleaned in a suitable solvent. All
parts should be disassembled before cleaning.
Parts should be thoroughly dried immediately after
cleaning. Use soft, clean, lintless rags. Parts may be dried
with cimpressed air. Do not allow the bearings to spin
while drying them with compressed air.
Inspection and Repair
It is very important to carefully and thoroughly inspect all
drive unit parts before reassembly.
Thorough inspection of the drive parts for wear or stress
and subsequent replacement of worn parts will eliminate
costly drive component repair after reassembly.
Axle Housing

The carrier bore for nicks or burrs that would prevent
the outer diameter of the pinion seal from sealing,
Remove any burrs that are found.

The bearing cap bores for nicks or burrs.
Remove any burrs that are found.

The housing for cracks. Replace the housing if any
cracks are found.

The housing for foreign material such as metal chips,
dirt, or rust.
Pinion and Ring Gear

Pinion and ring gear teeth for cracking, chipping,
scoring, or excessive wear.

Pinion splines for wear.

Pinion flange splines for wear.
The sealing surface of the pinion flange for nicks,
burrs, or rough tool marks which would cause
damage to the seal's inside diameter and result in an
oil leak.

Replace all worn or broken parts.

Ring and pinion gears are matched sets and are both
replaced anytime a replacement of either is
necessary.
Bearings

Bearings visually and by feel.

The bearings should feel smooth when oiled and
rotated while applying as much hand pressure as
possible.
The large end of the bearing rollers for wear.
This is where tapered roller bearing wear is most
evident.

Bearing cups for wear, cracks, brinelling and scoring.

Bearing and cups are only replaced as sets.

If the rear axle was operated for an extended period of
time with very loose bearings, the ring gear and drive
pinion will also require replacement.

Low mileage bearings may have minute scratches
and pits on the rollers and the bearing cups from the
initial pre-load. Do not replace a bearing for this
reason.

Bearing cups for cracks or chips.
Shims

Shims for cracks and chips. Damaged shims should
be replaced with an equally sized service shim.
Reassembly
1. Install pinion bearing races and baffle plate using
outer bearing race installer J±8611±01 / inner bearing
race installer J±42836 and drive handle J±8592.
NOTE: Baffle plate must be installed, when install the
inner pinion bearing race.
425RW019

5A±10BRAKE CONTROL SYSTEM
System Components
Electronic Hydraulic Control Unit (EHCU), three Wheel
Speed Sensors, Warning Light, and G-sensor.
Electronic Hydraulic Control Unit (EHCU)
The EHCU consists of ABS control circuits, fault detector,
and a fail-safe. The signal received from each sensor
activates the hydraulic unit accordingly and cancels the
ABS to return to normal braking if a malfunction occurs in
the ABS system.
The EHCU has a self-diagnosing function which can
indicate faulty circuits during diagnosis.
The EHCU is mounted on the engine compartment rear
right side. It consists of a Motor, Plunger Pump, Solenoid
Valves.
Solenoid Valves: Reduces or holds the caliper fluid
pressure for each front disc brake or both rear disc brakes
according to the signal sent from the EHCU.
Reservoir: Temporarily holds the brake fluid that returns
from the front and rear disc brake caliper so that pressure
of front disc brake caliper can be reduced smoothly.
Plunger Pump: Feeds the brake fluid held in the reservoir
to the master cylinder.
Motor: Drives the pump according to the signal from
EHCU.
Check Valve: Controls the brake fluid flow.
ABS Warning Light
821R200015Vehicles equipped with the Anti-lock Brake System have
an amber ªABSº warning light in the instrument panel.
The ªABSº warning light will illuminate if a malfunction in
the Anti-lock Brake System is detected by the Electronic
Hydraulic Control Unit (EHCU).In case of an electronic
malfunction, the EHCU will turn ªONº the ªABSº warning
light and disable the Anti-lock braking function.
The ªABSº light will turn ªONº for approximately three
seconds after the ignition switch is turned to the ªONº
position.If the ªABSº light stays ªONº after the ignition switch is
turned to the ªONº position, or comes ªONº and stays
ªONº while driving, the Anti-lock Brake System should be
inspected for a malfunction according to the diagnosis
procedure.
Wheel Speed Sensor
It consists of a sensor and a rotor. The sensor is attached
to the knuckle on the front wheels and to the rear axle
case on the rear differential.
The front sensor rotor is attached to the each brake rotor
by bolts.
The rear rotor is press-fit in the differential case.
The magnetic flux generated from electrodes magnetized
by a magnet in the sensor varies due to rotation of the
rotor, and the electromagnetic induction generates
alternating voltage in the coil. This voltage draws a ªsine
curveº with the frequency proportional to rotor speed and
it allows detection of wheel speed.
G-Sensor
The G-sensor installed inside the EHCU detects the
vehicle deceleration speed and sends a signal to the
EHCU. In 4WD operation, all four wheels may be
decelerated in almost the same phase, since all wheels
are connected mechanically.
This tendency is noticeable particularly on roads with low
friction coefficient, and the ABS control is adversely
affected.
The G-sensor judges whether the friction coefficient of
road surface is low or high, and changes the EHCU's
operating system to ensure ABS control.
Normal and Anti-lock Braking
Under normal driving conditions, the Anti-lock Brake
System functions the same as a standard power assisted
brake system. However, with the detection of wheel
lock-up, a slight bump or kick-back will be felt in the brake
pedal. This pedal ªbumpº will be followed by a series of
short pedal pulsations which occurs in rapid succession.
The brake pedal pulsation will continue until there is no
longer a need for the anti-lock function or until the vehicle
is stopped. A slight ticking or popping noise may be heard
during brake applications when the Anti-lock features is
being used.
When the Anti-lock feature is being used, the brake pedal
may rise even as the brakes are being applied. This is
also normal. Maintaining a constant force on the pedal
will provide the shortest stopping distance.
Brake Pedal Travel
Vehicles equipped with the Anti-lock Brake System may
be stopped by applying normal force to the brake pedal.
Although there is no need to push the pedal beyond the
point where it stops or holds the vehicle, by applying more
force the pedal will continue to travel toward the floor.
This extra brake pedal travel is normal.

5C±4
POWER±ASSISTED BRAKE SYSTEM
Disc Brake
Front Disc Brake
A05RW001
Rear Disc Brake (4y4 Model)
A05RW002
The disc brake assembly consists of a caliper, piston,
rotor, pad assembly and support bracket. The caliper
assembly has a single bore and is mounted to the support
bracket with two mounting bolts. The support bracket
allows the caliper to move laterally against the rotor. The
caliper is a one±piece casting with the inboard side
containing the piston bore. A square cut rubber seal is
located in a groove in the piston bore which provides the
hydraulic seal between the piston and the cylinder wall.
NOTE:
1. Replace all components included in repair kits used to
service this caliper.
2. Lubricate rubber parts with clean brake fluid to ease
assembly.3. If any hydraulic component is removed or
disconnected, it may be necessary to bleed all or part
of the brake system.
4. Replace pads in axle sets only.
5. The torque values specified are for dry, unlubricated
fasteners.
6. Perform the service operation on a clean bench free
from all mineral oil materials.
Operation
Hydraulic pressure, created by applying the brake pedal,
is converted by the caliper to a stopping force. This force
creates a clamping action of the piston pressing towards
the rotors (outward) and the caliper slides inward toward
the vehicle. This clamping action forces the linings
against the rotor, creating friction to stop the vehicle.

5C±10
POWER±ASSISTED BRAKE SYSTEM
Hydraulic Brakes
Filling Master Cylinder Reservoir
CAUTION: Use only specified brake fluid. Do not
use any fluid which contains a petroleum base. Do
not use a container which has been used for
petroleum based fluids or a container which is wet
with water. Petroleum based fluid will cause swelling
and distortion of rubber parts in the hydraulic brake
system. Water mixed with brake fluid lowers the fluid
boiling point. Keep all fluid containers capped to
prevent contamination.
Always fill the master cylinder reservoir when the en-
gine is cold.
Never allow the brake fluid to come in contact with
the painted surfaces.
The master cylinder reservoir must be kept properly
filled to ensure adequate reserve and to prevent air
and moisture from entering the hydraulic system.
However, because of expansion due to heat ab-
sorbed from the brakes and the engine, the reservoir
must not be overfilled. The brake fluid reservoir is on
the master cylinder, which is located under the hood
on the left side of the cowl. Thoroughly clean reser-
voir cap before removal to avoid getting dirt into res-
ervoir. Remove the diaphragm. Add fluid as required
to bring level to the ªMAXº mark on the reservoir
tank. Use ªDOT 3º Hydraulic Brake Fluid. If the fluid
cap diaphragm is stretched, return it to the original
position before installing.
Deterioration of Brake Fluid
Using any other brake fluid than specified or brake fluid
with mineral oil or water mixed in will drop the boiling point
of brake fluid. It may, in turn, result in vapor lock or
deteriorated rubber parts of the hydraulic system. Be sure
to change the brake fluid at specified intervals.
If the rubber parts are deteriorated, remove all the system
parts and clean them with alcohol. Prior to reassembly,
dry the cleaned parts with air to remove the alcohol.
Replace all the hoses and rubber parts of the system.
Leakage of Brake Fluid
With engine idling, set shift lever in the neutral position
and continue to depress brake pedal at a constant pedal
application force.
Should the pedal stroke become deeper gradually,
leakage from the hydraulic pressure system is possible.
Perform visual inspection for any signs of leakage.
Bleeding Brake Hydraulic System
A bleeding operation is necessary to remove air from the
hydraulic brake system whenever air is introduced into
the hydraulic system. It may be necessary to bleed the
hydraulic system at all four brakes if air has been
introduced through a low fluid level or by disconnecting
brake pipes at the master cylinder. If a brake pipe is
disconnected at one wheel, only that wheel
cylinder/caliper needs to be bled. If the pipes aredisconnected at any fitting located between the master
cylinder and brakes, then the brake system served by the
disconnected pipe must be bled.
1. For 4±Wheel Antilock Brake System (ABS) equipped
vehicle, be sure to remove the ABS main fuse 60A
located at the relay and fuse box before bleeding air. If
you attempt to bleed air without removing the main
fuse, air cannot be let out thoroughly, and this may
cause damage to the hydraulic unit. After bleeding air,
be sure to replace the ABS main fuse back to its
original position.
2. Set the parking brake completely, then start the
engine.
NOTE: The vacuum booster will be damaged if the
bleeding operation is performed with the engine off.
3. Remove the master cylinder reservoir cap.
4. Fill the master cylinder reservoir with brake fluid.
Keep the reservoir at least half full during the air
bleeding operation
5. Always use new brake fluid for replenishment.
6. When replenishing the brake fluid reservoir, carefully
pour in the brake fluid to prevent air bubbles from
entering the brake system.
When the master cylinder is replaced or overhauled,
first bleed the air from the master cylinder, then from
each wheel cylinder and caliper following the
procedures described below.
Bleeding the Master Cylinder
7. Disconnect the rear wheel brake pipe (1) from the
master cylinder.
Check the fluid level and replenish as necessary. If
replenished, leave the system for at least one minute.
8. Depress the brake pedal slowly once and hold it
depressed.
9. Completely seal the delivery port of the master
cylinder with your finger, where the pipe was
disconnected then release the brake pedal slowly.
10. Release your finger from the delivery port when the
brake pedal returns completely.
11. Repeat steps 8 through 10 until the brake fluid comes
out of the delivery port during step 8.
NOTE: Do not allow the fluid level in the reservoir to go
below the half±way mark.
12. Reconnect the brake pipe (1) to the master cylinder
and tighten the pipe.
13. Depress the brake pedal slowly once and hold it
depressed.
14. Loosen the rear wheel brake pipe (1) at the master
cylinder.
15. Retighten the brake pipe, then release the brake
pedal slowly.
16. Repeat steps 13 through 15 until no air comes out of
the port when the brake pipe is loosened
NOTE: Be very careful not to allow the brake fluid to come
in contact with painted surfaces.