park assist ISUZU TROOPER 1995 Workshop Manual

DIAGNOSIS 3-5
POWER STEERING SYSTEM DIAGNOSIS
HISSING NOISE
There is some noise in all power steering systems. One of the most common is a hissing sound when the steering
wheel is fully turned and the car is not moving. This noise will be most evident when the wheel is operated while
the brakes are applied. There is no relationship between this noise and steering performance. Do not replace the
valve unless the "hissing" noise is extremely objectionable. A replacement valve will also have a slight noise, and
is
not always a cure for the condition.
Condition
Possible Cause Correction
Rattle or Chucking 1. Pressure
hose touching other parts of vehicle. Adjust hose position. Do not
Noise bend
tubing by hand.
2. Tie rod ends loose. Tighten or replace tie rod
end.
3. Loose steering gear mounting. Tighten
steering gear
mounting.
4. Steering gear misadjustment. Check and adjust steering
gear
preload.
Poor Return of Steering 1. Improper front wheel alignment. Adjust front wheel
Wheel
to Center alignment.
2. Wheel bearing worn. Replace front wheel
bearing.
3. Tie rod end binding. Replace tie rod end.
4. Ball joint binding. Replace ball joint.
5. Tight or frozen steering shaft bearing. Replace steering assembly.
6. Steering gear misadjustment. Adjust the steering gear.
7. Sticky or plugged steering gear valve. Repair or replace steering
gear
valve.
8. Entry of air in the power steering system. Bleed the system.
Momentary Increase In 1. High internal leakage. Repair steering gear.
Effort When Turning
2. Power steering fluid level low. Replenish
fluid.
Wheel
Fast To Right or
Left
Steering
Wheel Surges 1. Insufficient pump pressure. Repair pump assembly.
or Jerks
When Turning 2. Sticky steering gear valve. Repair or replace steering
Especially During gear.
Parking
3. Power steering fluid level low. Replenish
fluid.
Excessive Wheel Kick 1. Air in system. Bleed hydraulic system.
Back
or Loose Steering 2. Tie rod end loose. Tighten tie rod end.
3. Wheel bearing worn. Replace wheel bearing.
Hard Steering
or Lack 1. Sticky steering gear valve. Repair or replace steering
or Power Assist gear valve.
2. Insufficient pump pressure.
Repair pump assembly.
3. Excessive internal pump leakage. Repair
pump assembly.
4. Excessive internal steering gear leakage. Repair steering gear
5. Power steering fluid level low. Replenish
fluid.

6E2-12 DRIVEABILITY AND EMISSIONS
L-LITER
A metric unit of capacity.
MALFUNCTION
A problem that causes the system to operate
incorrectly. Typical malfunctions are wiring harness
opens
or shorts, failed sensors or circuit components.
MAP-MANIFOLD ABSOLUTE PRESSURE
Air pressure in the intake manifold with reference to
zero or absolute vacuum.
MPH-MILE PER HOUR
A unit measuring speed needed to travel distance of
one mile (5280 feet) in one hour.
MIT -MANUAL TRANSMISSION
N.C.-NORMALLY CLOSED
State of relay contacts or solenoid plunger is close
when voltage is not applied.
N·m-NEWTON METER (Torque)
A metric unit describing force.
N.M.-NORMALLY OPEN
State of relay contacts or solenoid plung&r' is open
when voltage is applied.
NOx-NITROGEN OXIDES
One of the pullutants found in engirie exhaust.
02-0XYGEN (Sensor)
Monitors the oxygen contel)f of the exhaust system
and generates a
voltage signal to the Engine Control
Module (ECM).
OUTPUT
Result of a functi typically controlled by the ECM.
OXYGEN SE OR
Device that etects the amount of oxygen (02) in the
exhaust
stfeam. /
PCV-~OSITIVE CRANKCASE VENTILATION
Prey£nt fumes in crankcase from passing into
atmosphere.
PNP-PARK/NEUTRAL POSITION
PORT-EXHAUST OR INTAKE PORT
PWM-PULSE WIDTH MODULATE
RPM-REVOLUTION PER MINUTE
A measure of rotational speed.
SELF-DIAGNOSTIC TROl)SLE CODE
The ECM can detect malfunctions in the system. If a
malfunction occurs, the ECM turns on the malfunction
indicator lamp. A OTC can be obtained from the ECM
through the malfunction indicator lamp. This DTC will
indicate the area of the malfunction.
TACH-TACHOMETER
TB-THROTTLE BODY
TBI-THROTTLE BODY FUEL INJECTION
Computer Command Control using throttle body fuel
injection
TP SENSOR-THROTTLE POSITION SENSOR
VACUUM
Negative pressure; less than atmospheric pressure.
VIN-VEHICLE IDENTIFICATION NUMBER
VSS-VEHICLE SPEED SENSOR
Sensor which sends vehicle speed information to the
ECM.
VSV-VACUUM SWITCH VALVE
(Electronically Controlled)
VSV-VACUUM SWITCH VALVE
Temperature controlled vacuum switch, that is used to
route or exhaust vacuum at various engine
temperatures.
WOT -WIDE OPEN THROTTLE
DRIVEABILITV AND EMISSION SECTION SUMMARY
The Driveability and Emissions Sections are sub­
divided into three sub sections:
SECTION A: CIRCUIT INFORMATION &
DIAGNOSIS
• Component Locations
• Wiring Diagrams
• ECM Terminal End View and Terminal
Definitions
• On-Board Diagnostic System Check. This
must be the first step of any diagnostic
procedure.
• DTC Charts with facing pages containing
circuit diagrams, circuit operation
information, and
helpful diagnostic
information.
SECTION B: DRIVEABILITY & EMISSIONS
SYMPTONS
• This sub-section assists in diagnosis of
intermittent problems or problems which
don't result in the storing of DTC(s). It is
arranged
by symptoms of poor driveability
and emissions and lists possible causes of
the problems.
SECTION C: COMPONENT CHECKS &
SERVICE
• Component and Circuit Descriptions
• On-Vehicle Service
• Functional
Checks/Diagnostic Charts
•