sensor ISUZU TROOPER 1998 Service Repair Manual

6E±346
ENGINE DRIVEABILITY AND EMISSIONS

Crankshaft position (58X reference).

Camshaft position (CMP) sensor.

Engine coolant temperature (ECT) sensor.

Throttle position (TP) sensor.

Knock signal (knock sensor).

Park/Neutral position (PRNDL input).

Vehicle speed (vehicle speed sensor).

PCM and ignition system supply voltage.

The crankshaft positron (CKP) sensor sends the
PCM a 58X signal related to the exact position of the
crankshaft.
TS22909

The camshaft position (CMP) sensor sends a signal
related to the position of the camshaft.
TS22910

The knock sensor tells the PCM if there is any
problem with pre-ignition or detonation. This
information allows the PCM to retard timing, if
necessary.
TS24037
Based on these sensor signals and engine load
information, the PCM sends 5V to each ignition coil.
060RW015
The PCM applies 5V signal voltage to the ignition coil
requiring ignition. This signal sets on the power transistor
of the ignition coil to establish a grounding circuit for the
primary coil, applying battery voltage to the primary coil.
At the ignition timing, the PCM stops sending the 5V
signal voltage. Under this condition the power transistor
of the ignition coil is set off to cut the battery voltage to the
primary coil, thereby causing a magnetic field generated
in the primary coil to collapse. On this moment a line of
magnetic force flows to the secondary coil, and when this
magnetic line crosses the coil, high voltage induced by

6E±347 ENGINE DRIVEABILITY AND EMISSIONS
the secondary ignition circuit to flow through the spark
plug to the ground.
TS24047
Ignition Control PCM Output
The PCM provides a zero volt (actually about 100 mV to
200 mV) or a 5-volt output signal to the ignition control (IC)
module. Each spark plug has its own primary and
secondary coil module (ºcoil-at-plugº) located at the spark
plug itself. When the ignition coil receives the 5-volt signal
from the PCM, it provides a ground path for the B+ supply
to the primary side of the coil-at -plug module. This
energizes the primary coil and creates a magnetic field in
the coil-at-plug module. When the PCM shuts off the
5-volt signal to the ignition control module, the ground
path for the primary coil is broken. The magnetic field
collapses and induces a high voltage secondary impulse
which fires the spark plug and ignites the air/fuel mixture.
The circuit between the PCM and the ignition coil is
monitored for open circuits, shorts to voltage, and shorts
to ground. If the PCM detects one of these events, it will
set one of the following DTCs:

P0351: Ignition coil Fault on Cylinder #1

P0352: Ignition coil Fault on Cylinder #2

P0353: Ignition coil Fault on Cylinder #3

P0354: Ignition coil Fault on Cylinder #4

P0355: Ignition coil Fault on Cylinder #5

P0356: Ignition coil Fault on Cylinder #6
Knock Sensor (KS) PCM Input
The knock sensor (KS) system is comprised of a knock
sensor and the PCM. The PCM monitors the KS signals
to determine when engine detonation occurs. When a
knock sensor detects detonation, the PCM retards the
spark timing to reduce detonation. Timing may also be
retarded because of excessive mechanical engine or
transmission noise.
Powertrain Control Module (PCM)
The PCM is responsible for maintaining proper spark and
fuel injection timing for all driving conditions. To provideoptimum driveability and emissions, the PCM monitors
the input signals from the following components in order
to calculate spark timing:

Engine coolant temperature (ECT) sensor.

Intake air temperature (IAT) sensor.

Mass air flow (MAF) sensor.

PRNDL input from transmission range switch.

Throttle position (TP) sensor.

Vehicle speed sensor (VSS) .

Crankshaft position (CKP) sensor.
Spark Plug
Although worn or dirty spark plugs may give satisfactory
operation at idling speed, they frequency fail at higher
engine speeds. Faulty spark plugs may cause poor fuel
economy, power loss, loss of speed, hard starting and
generally poor engine performance. Follow the
scheduled maintenance service recommendations to
ensure satisfactory spark plug performance. Refer to
Maintenance and Lubrication.
Normal spark plug operation will result in brown to
grayish-tan deposits appearing on the insulator portion of
the spark plug. A small amount of red-brown, yellow, and
white powdery material may also be present on the
insulator tip around the center electrode. These deposits
are normal combustion by-products of fuels and
lubricating oils with additives. Some electrode wear will
also occur. Engines which are not running properly are
often referred to as ªmisfiring.º This means the ignition
spark is not igniting the air/fuel mixture at the proper time.
While other ignition and fuel system causes must also be
considered, possible causes include ignition system
conditions which allow the spark voltage to reach ground
in some other manner than by jumping across the air gap
at the tip of the spark plug, leaving the air/fuel mixture
unburned. Misfiring may also occur when the tip of the
spark plug becomes overheated and ignites the mixture
before the spark jumps. This is referred to as
ªpre-ignition.º
Spark plugs may also misfire due to fouling, excessive
gap, or a cracked or broken insulator. If misfiring occurs
before the recommended replacement interval, locate
and correct the cause.
Carbon fouling of the spark plug is indicated by dry, black
carbon (soot) deposits on the portion of the spark plug in
the cylinder. Excessive idling and slow speeds under
light engine loads can keep the spark plug temperatures
so low that these deposits are not burned off. Very rich
fuel mixtures or poor ignition system output may also be
the cause. Refer to DTC P0172.
Oil fouling of the spark plug is indicated by wet oily
deposits on the portion of the spark plug in the cylinder,
usually with little electrode wear. This may be caused by
oil during break-in of new or newly overhauled engines.
Deposit fouling of the spark plug occurs when the normal
red-brown, yellow or white deposits of combustion by
products become sufficient to cause misfiring. In some
cases, these deposits may melt and form a shiny glaze on
the insulator around the center electrode. If the fouling is
found in only one or two cylinders, valve stem clearances
or intake valve seals may be allowing excess lubricating

6E±349 ENGINE DRIVEABILITY AND EMISSIONS

Damage during re-gapping can happen if the gapping
tool is pushed against the center electrode or the
insulator around it, causing the insulator to crack.
When re-gapping a spark plug, make the adjustment
by bending only the ground side terminal, keeping the
tool clear of other parts.

ºHeat shockº breakage in the lower insulator tip
generally occurs during several engine operating
conditions (high speeds or heavy loading) and may be
caused by over-advanced timing or low grade fuels.
Heat shock refers to a rapid increase in the tip
temperature that causes the insulator material to
crack.
Spark plugs with less than the recommended amount of
service can sometimes be cleaned and re-gapped , then
returned to service. However, if there is any doubt about
the serviceability of a spark plug, replace it. Spark plugs
with cracked or broken insulators should always be
replaced.
A/C Clutch Diagnosis
A/C Clutch Circuit Operation
A 12-volt signal is supplied to the A/C request input of the
PCM when the A/C is selected through the A/C control
switch.
The A/C compressor clutch relay is controlled through the
PCM. This allows the PCM to modify the idle air control
position prior to the A/C clutch engagement for better idle
quality. If the engine operating conditions are within their
specified calibrated acceptable ranges, the PCM will
enable the A/C compressor relay. This is done by
providing a ground path for the A/C relay coil within the
PCM. When the A/C compressor relay is enabled,
battery voltage is supplied to the compressor clutch coil.
The PCM will enable the A/C compressor clutch
whenever the engine is running and the A/C has been
requested. The PCM will not enable the A/C compressor
clutch if any of the following conditions are met:

The throttle is greater than 90%.

The engine speed is greater than 6315 RPM.

The ECT is greater than 119
C (246
F).

The IAT is less than 5
C (41
F).

The throttle is more than 80% open.
A/C Clutch Circuit Purpose
The A/C compressor operation is controlled by the
powertrain control module (PCM) for the following
reasons:

It improvises idle quality during compressor clutch
engagement.

It improvises wide open throttle (WOT) performance.

It provides A/C compressor protection from operation
with incorrect refrigerant pressures.
The A/C electrical system consists of the following
components:

The A/C control head.

The A/C refrigerant pressure switches.

The A/C compressor clutch.

The A/C compressor clutch relay.
The PCM.
A/C Request Signal
This signal tells the PCM when the A/C mode is selected
at the A/C control head. The PCM uses this to adjust the
idle speed before turning on the A/C clutch. The A/C
compressor will be inoperative if this signal is not
available to the PCM.
Refer to
A/C Clutch Circuit Diagnosis for A/C wiring
diagrams and diagnosis for A/C electrical system.
General Description (Exhaust Gas
Recirculation (EGR) System)
EGR Purpose
The exhaust gas recirculation (EGR) system is use to
reduce emission levels of oxides of nitrogen (NOx). NOx
emission levels are caused by a high combustion
temperature. The EGR system lowers the NOx emission
levels by decreasing the combustion temperature.
057RW002
Linear EGR Valve
The main element of the system is the linear EGR valve.
The EGR valve feeds small amounts of exhaust gas back
into the combustion chamber. The fuel/air mixture will be
diluted and combustion temperatures reduced.
Linear EGR Control
The PCM monitors the EGR actual positron and adjusts
the pintle position accordingly. The uses information from
the following sensors to control the pintle position:

Engine coolant temperature (ECT) sensor.

Throttle position (TP) sensor.

Mass air flow (MAF) sensor.
Linear EGR Valve Operation and Results
of Incorrect Operation
The linear EGR valve is designed to accurately supply
EGR to the engine independent of intake manifold
vacuum. The valve controls EGR flow from the exhaust

6E±350
ENGINE DRIVEABILITY AND EMISSIONS
to the intake manifold through an orifice with a PCM
controlled pintle. During operation, the PCM controls
pintle position by monitoring the pintle position feedback
signal. The feedback signal can be monitored with Tech 2
as ªActual EGR Pos.º ªActual EGR Pos.º should always
be near the commanded EGR position (ºDesired EGR
Pos.º). If a problem with the EGR system will not allow the
PCM to control the pintle position properly, DTC P1406
will set. The PCM also tests for EGR flow. If incorrect flow
is detected, DTC P0401 will set. If DTCs P0401 and/or
P1406 are set, refer to the DTC charts.
The linear EGR valve is usually activated under the
following conditions:

Warm engine operation.

Above-idle speed.
Too much EGR flow at idle, cruise or cold operation may
cause any of the following conditions to occur:

Engine stalls after a cold start.

Engine stalls at idle after deceleration.

Vehicle surges during cruise.

Rough idle.
Too little or no EGR flow may allow combustion
temperatures to get too high. This could cause:

Spark knock (detonation).

Engine overheating.

Emission test failure.

DTC P0401 (EGR flow test).

Poor fuel economy.
0017
EGR Pintle Position Sensor
The PCM monitors the EGR valve pintle position input to
endure that the valve responds properly to commands
from the PCM and to detect a fault if the pintle position
sensor and control circuits are open or shorted. If the
PCM detects a pintle position signal voltage outside the
normal range of the pintle position sensor, or a signal
voltage that is not within a tolerance considered
acceptable for proper EGR system operation, the PCM
will set DTC P1406.
General Description (Positive
Crankcase Ventilation (PCV) System)
Crankcase Ventilation System Purpose
The crankcase ventilation system is use to consume
crankcase vapors in the combustion process instead of
venting them to the atmosphere. Fresh air from the
throttle body is supplied to the crankcase and mixed with
blow-by gases. This mixture is then passed through the
positive crankcase ventilation (PCV) valve into the
common chamber.
Crankcase Ventilation System Operation
The primary control is through the positive crankcase
ventilation (PCV) valve. The PCV valve meters the flow at
a rate that depends on the intake vacuum. The PCV valve
restricts the flow when the inlet vacuum is highest. In
addition, the PCV valve can seal the common chamber
off in case of sudden high pressure in the crankcase.
028RV002
While the engine is running, exhaust fuses and small
amounts of the fuel/air mixture escape past the piston

6E±353 ENGINE DRIVEABILITY AND EMISSIONS
ILLUSTRATIONTOOL NO.
TOOL NAME
5-8840-0285-0
(J 39200)
High Impedance
Multimeter (Digital
Voltmeter ± DVM)
(1) PCMCIA Card
(2) RS232 Loop Back
Connector
(3) SAE 16/19 Adapter
(4) DLC Cable
(5) TECH±2
5-8840-0607-0
(J 34142-B)
Unpowered Test Light
5-8840-0385-0
(J 35616-A/BT-8637)
Connector Test
Adapter Kit
5-8840-0383-0
(J 26792/BT-7220-1)
Spark Tester
5-8840-0279-0
(J 23738-A)
Vacuum Pump with
Gauge common tool
ILLUSTRATIONTOOL NO.
TOOL NAME
BT-8515
Exhaust Back Pressure
Tester or common tool
5-8840-2640-0
(J 39194-B)
Heated Oxygen Sensor
Wrench
5-8840-0632-0
(J 35689-A)
Terminal Remover
5-8840-0388-0
(J 28742-A)
Weather Pack II
Terminal Remover
5-8840-2635-0
(J 39021-90)
Injector Switch Box
5-8840-2636-0
(J 39021-65)
Injector Test Light

6F±4ENGINE EXHAUST
Front Exhaust Pipe
Front Exhaust Pipe and Associated Parts
150RW063
Legend
(1) Front Exhaust Pipe RH Fixing Nuts
(2) Front Exhaust Pipe RH Fixing Bolts and Nuts
(3) O
2 Sensor Terminal Connector (for IGM)
(4) Front Exhaust Pipe LH Fixing Nuts(5) Front Exhaust Pipe LH Fixing Bolts and Nuts
(6) Front Exhaust Pipe LH
(7) Front Exhaust Pipe RH
(8) Three way Exhaust Pipe Fixing Bolts and Nuts
Removal
1. Disconnect battery ground cable.
2. Raise the vehicle and support with suitable safety
stands.
3. Disconnect O
2 sensor harness connector (3).
4. Remove front exhaust pipe fixing nuts and three way
Exhaust Pipe Fixing Bolts and Nuts (2)(5)(8).
5. Remove front exhaust pipe fixing three stud nuts from
exhaust manifold (1)(4).
6. Remove front exhaust pipe (6)(7).
Installation
1. Install front exhaust pipe (6)(7) and tighten three stud
nuts (1)(4) and nuts (2)(5)(8) to the specified torque.
Torque
Stud Nuts : 67 N´m (6.8 Kg´m/49 lb ft)
Nuts : 43 N´m (4.3 Kg´m/32 lb ft)
2. Reconnect O
2 sensor harness connector (3).

6J±2
INDUCTION
Air Cleaner Element
Removal
1. Remove positive ventilation hose from connector(1).
2. Remove intake air temperature sensor(2).
3. Remove air flow sensor(3).
4. Remove air cleaner duct cover(4).
5. Remove air cleaner element(5).
130RW003
Inspection
Check the air cleaner element for damage or dust
clogging. Replace if it is damaged, or clean if it is clogged.
Cleaning Method
Tap the air cleaner element gently so as not to damage
the paper element, or clean the element by blowing with
compressed air of about 490 kPa (71 psi) from the clean
side if it is extremely dirty.
130RW002
Installation
1. Install air cleaner element(5).
2. Attach the air cleaner duct cover (4) to the body
completely, then clamp it with the clip.
3. Install mass air flow sensor(3).
4. Install air temperature sensor(2).
5. Connect positive crankcase ventilation hose to
connector(1).
For General Export Model
130RW003
For Isuzu General Motors (IGM) Model
130RW006

SERVICE INFORMATION 00 Ð 5
Idling improperly adjusted Adjust the idling Idling system
Checkpoint Possible cause Correction
Defective fast idling speed control device Repair or replace the fast idling
speed control device Fast idling speed
control device
Accelerator control system improperly
adjustedAdjust the accelerator control
system Accelerator control
system
2. UNSTABLE IDLING
4. QUICK-ON START SYSTEM (QOS III)
PREPARATION
1. Disconnect the thermoswitch connector.
2. Determine whether or not the glow plugs are receiving power.
a) Make sure that the starter switch is "OFF"
b) Connect a voltmeter between one of the glow plugs and the cylinder wall.
c) Move the starter switch to the "ON" position.
The voltmeter needle will show the souse voltage (12V) if the glow plugs are receiving power.
If the voltmeter needle does not move, the glow plugs are not receiving power.
3. Perform the troubleshooting procedure.
1.
2.
3.Replace the fusible link wire
Replace the indicator light fuse
Replace the indicator light bulb Glow plug indicator
light does not turn
on.Defective Fusible link wire
Broken indicator light fuse
Defective indicator light bulb
1.
2.
3.
4.Replace the fusible link wire
Replace or Repair glow plug relay
connector
Replace or Repair glow plug
connector
Replace or Repair quick-on start
timer connector Preheating system
does not workDefective Fusible link wire shorted
Defective glow plug relay connector
Defective glow plug connector
Defective quick-on start timer connector
1.
2.
3.Replace thermo sensor or repair
wiring harness.
Replace glow plug
Replace timer unit Preheating time to
long or to shortDefective thermo sensor include
defective wiring harness
Defective glow plug
Defective timer unit

SERVICE INFORMATION 00 Ð 29
FUEL SYSTEM
Fuel Filter
Replacement Procedure
1. Loosen the used fuel filter by turning it counterclock-
wise with the filter wrench.
Filter Wrench: 5-8840-0253-0 (J-22700)
2. Remove the level sensor from the filter by turning it
counterclockwise with a wrench.
3. Install the level sensor to the new fuel filter with a
wrench.
5. Apply a light coat of engine oil to the O-ring.
6. Turn in the fuel filter until the sealing face comes in
contact with the O-ring.
7. Turn in the fuel filter an additional 2/3 of a turn with a
filter wrench.
Filter Wrench: 5-8840-0253-0 (J-22700)
8. Loosen the bleeder plug on the injection pump overflow
valve.
9. Operate the priming pump until fuel begins to flow from
the fuel filter.
10. Retighten the bleeder plug.
11. Operate the priming pump several times and check for
fuel leakage.
NOTE:
The use of an ISUZU genuine fuel filter is strongly recom-
mended.
13 (1.3/9)
N·m (Kg·m/lb·ft) Level Sensor Torque
4. Clean the filter cover fitting faces.
This will allow the new fuel filter to seat properly.

SERVICE INFORMATION 00 Ð 37
3. Measure the glow plug terminal voltage with a circuit
tester immediately after turning the starter switch to the
ÒONÓ position.
8 – 9
V Glow Plug Terminal Voltage
QUICK-ON START III SYSTEM
Quick-On Start System Inspection Procedure
1. Disconnect the thermo-sensor connection on the ther-
mostat outlet pipe.
2. Turn the starter switch to the ÒONÓ position.
If the Quick-On Start III System is operating properly,
the glow relay will make a clicking sound within seven
seconds after the starter switch is turned on.
NOTE:
Electrical power to the quick-on start system will be cut
after the starter has remained in the ÒONÓ position for ten
seconds.
Turn the starter switch to the ÒOFFÓ position and back to
the ÒONÓ position.
This will reset the Quick-On Start III System.
Nut and Bolt Angular Tightening Method
(Using The Special Tool)
1. Carefully wash the nuts and bolts to remove all oil and
grease.
2. Apply engine oil to the threads and setting faces of the
nuts and bolts.
3. Use a torque wrench to tighten the nuts and bolts to the
specified torque (snug torque).
4. Attach the angle gauge to the socket wrench.
Angle Gauge: 5-88400-266-0
5. Attach a magnet to some part to hold the angle gauge
stationary.
6. Tighten the nuts and bolts to the specified angle, noting
the angle gauge indication.