reset ISUZU TROOPER 1998 Service Owner's Manual

6E±343 ENGINE DRIVEABILITY AND EMISSIONS
constant measuring and adjusting of the air/fuel ratio, the
fuel injection system is called a ªclosed loopº system.
The PCM monitors signals from several sensors in order
to determine the fuel needs of the engine. Fuel is
delivered under one of several conditions called ªmodes.º
All modes are controlled by the PCM.
Fuel Pressure Regulator
The fuel pressure regulator is a diaphragm-operated
relief valve mounted on the fuel rail with fuel pump
pressure on one side and manifold pressure on the other
side. The fuel pressure regulator maintains the fuel
pressure available to the injector at three times
barometric pressure adjusted for engine load. It may be
serviced separate.
If the pressure is too low, poor performance and a DTC
P0131, DTC P0151,DTC P0171 or DTC P1171 will be the
result. If the pressure is too high, excessive odor and/or a
DTC P0132, DTC P0152,DTC P0172 or DTC P0175 will
be the result. Refer to
Fuel System Diagnosis for
information on diagnosing fuel pressure conditions.
0011
Fuel Pump Electrical Circuit
When the key is first turned ªON,º the PCM energizes the
fuel pump relay for two seconds to build up the fuel
pressure quickly. If the engine is not started within two
seconds, the PCM shuts the fuel pump off and waits until
the engine is cranked. When the engine is cranked and
the 58 X crankshaft position signal has been detected by
the PCM, the PCM supplies 12 volts to the fuel pump relay
to energize the electric in-tank fuel pump.
An inoperative fuel pump will cause a ªno-startº condition.
A fuel pump which does not provide enough pressure will
result in poor performance.
Fuel Rail
The fuel rail is mounted to the top of the engine and
distributes fuel to the individual injectors. Fuel is
delivered to the fuel inlet tube of the fuel rail by the fuel
lines. The fuel goes through the fuel rail to the fuel
pressure regulator. The fuel pressure regulator maintainsa constant fuel pressure at the injectors. Remaining fuel
is then returned to the fuel tank.
055RW009
Idle Air Control (IAC) Valve
The purpose of the idle air control (IAC) valve is to control
engine idle speed, while preventing stalls due to changes
in engine load. The IAC valve, mounted in the throttle
body, controls bypass air around the throttle plate. By
moving the conical valve (pintle) in (to decrease air flow)
or out (to increase air flow), a controlled amount of air can
move around the throttle plate. If the RPM is too low, the
PCM will retract the IAC pintle, resulting in more air
moving past the throttle plate to increase the RPM. If the
RPM is too high, the PCM will extend the IAC pintle,
allowing less air to move past the throttle plate,
decreasing the RPM.
The IAC pintle valve moves in small steps called counts.
During idle, the proper position of the IAC pintle is
calculated by the PCM based on battery voltage, coolant
temperature, engine load, and engine RPM. If the RPM
drops below a specified value, and the throttle plate is
closed, the PCM senses a near-stall condition. The PCM
will then calculate a new IAC pintle valve position to
prevent stalls.
If the IAC valve is disconnected and reconnected with the
engine running, the idle RPM will be wrong. In this case,
the IAC must be reset. The IAC resets when the key is
cycled ªONº then ªOFF.º When servicing the IAC, it
should only be disconnected or connected with the
ignition ªOFF.º
The position of the IAC pintle valve affects engine start-up
and the idle characteristics of the vehicle. If the IAC pintle
is fully open, too much air will be allowed into the manifold.
This results in high idle speed, along with possible hard
starting and a lean air/fuel ratio. DTC P0507 or DTC
P1509 may set. If the IAC pintle is stuck closed, too little
air will be allowed in the manifold. This results in a low idle
speed, along with possible hard starting and a rich air/fuel
ratio. DTC P0506 or DTC P1508 may set. If the IAC
pintle is stuck part-way open, the idle may be high or low
and will not respond to changes in the engine load.

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.

6D6 Ð 4 QOS III PREHEATING SYSTEM
QOS III BLOCK CHART
“ST” detection“ST”
Indicator timer
11
1“ON”
“ST” “ON”13
tdDelay timer
¡C
td
¡CResetReset5
ta
Afterglow timer
Coolant temperature sensor
70¡CAll reset
12
Vehicle speed detection
9 Km/h18 Km/h
Complete combustion detection
STALLRUN
Set 8
4
9
6
10
Thermo-sensor
Speed sensor
Generator
Charge relay
Glow relay No. 1
Glow lamp
(12V, 3.4 W)
Glow relay No. 2
Glow plug
Battery 12VStarter SW
“OFF” “ST” “ACC” “ON”
: Indicator lamp light – up time
: Quick afterglow time
: Afterglow time ti
td
ta7
2
3
Dropping
register

ENGINE MECHANICAL 6A – 13
VALVE CLEARANCE ADJUSTMENT
1. Install 2.80 mm valve adjuster (shim) first when
reassembling the engine.
Thickness mark faces down.
2. Measure the valve clearance after installing cam
carrier assy with camshafts.
3. Change the adjuster using a special tool when the
clearance is out of tolerance.
Valve Clearance Adjusting Tool: 5-8840-2590-0
VALVE CLEARANCE (When cold condition)
Inlet 0.15 ± 0.05 mm
Exh 0.25 ± 0.05 mm
COMPRESSION PRESSURE
MEASUREMENT
1. Start the engine and allow it to idle until the coolant
temperature reaches 70 – 80°C (158 – 176°F).
2. Remove the following parts.
•Glow plugs
•Fuel cut solenoid connector
•QOS (Quick-On Start System) fuse in the fuse
box.
3. Set the adapter and compression gauge to the No.
1 cylinder glow plug hole.
Compression Gauge
(with Adapter): 5-8840-2008-0
4. Turn the engine over with the starter motor and take
the compression gauge reading.
Compression Pressure at 200 rpm
Standard: 3040 kPa (31 kg/cm
2/441 psi)
Limit: 2160 kPa (22 kg/cm
2/313 psi)
5. Repeat the procedure (Steps 3 and 4) for the
remaining cylinders.
QUICK-ON START 4 SYSTEM
Quick-On Start System Inspection Procedure
1. Disconnect the ECT-sensor connection around the
thermostat outlet pipe.
2. Turn the starter switch to the “ON” position.
If the Quick-On Start 4 System is operating
properly, the glow relay will make a clicking sound
within seven seconds after the starter switch is
turned on.
3. Measure the glow plug terminal voltage with a
circuit tester immediately after turning the starter
switch to the “ON” position.
Glow Plug Terminal Voltage: approx. 12V
NOTE: Electrical power to the quick-on start system will
be cut after the starter has remained in the “ON”
position for twenty seconds.
Turn the starter switch to the “OFF” position and back
to the “ON” position.
This will reset the Quick-On Start 4 System.
014RW150

6E±28
4JX1±TC ENGINE DRIVEABILITY AND EMISSIONS
in the ECM's memory, the DTC(s) will be output from the
lowest to the highest, with each DTC being displayed
three times.
The DTC display will continue as long as the DLC is
shorted.
Reading Diagnostic Trouble Codes Using
a TECH 2
The procedure for reading diagnostic trouble code(s) is to
used a diagnostic Tech 2. When reading DTC(s), follow
instructions supplied by Tech 2 manufacturer.
For the 1998 model year, Isuzu dealer service
departments will continue to use Tech 2.
Clearing Diagnostic Trouble Codes
IMPORTANT:Do not clear DTCs unless directed to do
so by the service information provided for each diagnostic
procedure. When DTCs are cleared, the Freeze Frame
and Failure Record data which may help diagnose an
intermittent fault will also be erased from memory.
If the fault that caused the DTC to be stored into memory
has been corrected, the Diagnostic Executive will begin to
count the ªwarm-upº cycles with no further faults
detected, the DTC will automatically be cleared from the
ECM memory.To clear Diagnostic Trouble Codes (DTCs), use the Tech
2 ªclear DTCsº or ªclear informationº function. When
clearing DTCs follow instructions supplied by the Tech 2
manufacturer.
When a Tech 2 is not available, DTCs can also be cleared
by disconnecting
one of the following sources for at least
thirty (30) seconds.
NOTE: To prevent system damage, the ignition key must
be ªOFFº when disconnecting or reconnecting battery
power.

The power source to the control module. Examples:
fuse, pigtail at battery ECM connectors etc.

The negative battery cable. (Disconnecting the
negative battery cable will result in the loss of other
on-board memory data, such as preset radio tuning).
060RW169

6E±41 4JX1±TC ENGINE DRIVEABILITY AND EMISSIONS
EGR (Exhaust Gas Recirculation)
Diagnosis

A diagnosis of the EGR system is covered by DTC
P1403.

EGR VSV circuit diagnosis is covered by DTC P1404.

EGR pressure sensor diagnosis is covered by DTC
P405 and/or P406.

EGR EVRV circuit diagnosis is covered by DTC
P1405. Refer to the DTC charts.
Tech 2 Data Definitions and Ranges
A/C CLUTCH±Tech 2 Displays ON or OFF±
Indicates whether the A/C has commanded the A/C
clutch ON.
MAP kPa Ð Tech 2 Range 10-105 kPa/0.00-5.00
Volts Ð
The manifold absolute pressure reading is determined
from the MAP sensor signal monitored during key up and
wide open throttle (WOT) conditions. The manifold
absolute pressure is used to compensate for altitude
differences and is normally displayed around ª61-104º
depending on altitude and manifold absolute pressure.
CMP ACT. COUNTER ±Cam Position
DESIRED IDLE Ð Tech 2 Range 0-3187 RPM Ð
The idle speed that the ECM is commanding. The ECM
will compensate for various engine loads based on engine
coolant temperature, to keep the engine at the desired
speed.
ECT Ð (Engine Coolant Temperature) Tech 2
Range ±40
C to 151
C (±40
F to 304
F) Ð
The engine coolant temperature (ECT) is mounted in the
coolant stream and sends engine temperature
information to the ECM. The ECM applies 5 volts to the
ECT sensor circuit. The sensor is a thermistor which
changes internal resistance as temperature changes.
When the sensor is cold (high resistance), the ECM
monitors a high signal voltage and interprets that as a cold
engine. As the sensor warms (decreasing resistance),
the voltage signal will decrease and the ECM will interpret
the lower voltage as a warm engine.
ENGINE RUN TIME Ð Tech 2 Range
00:00:00-99:99:99 Hrs:Min:Sec Ð
Indicates the time elapsed since the engine was started.
If the engine is stopped, engine run time will be reset to
00:00:00.
ENGINE SPEED Ð Range 0-9999 RPM Ð
Engine speed is computed by the ECM from the 57X
reference input. It should remain close to desired idle
under various engine loads with engine idling.Air Intake Valve meter POSITION Ð Tech 2 Range
0-100 % Ð
IAT (INTAKE AIR TEMPERATURE)Ð Tech 2 Range
±40
C to 151
C (±40
F to 304
F) Ð
The ECM converts the resistance of the intake air
temperature sensor to degrees. Intake air temperature
(IAT) is used by the ECM to adjust fuel delivery and spark
timing according to incoming air density.
MAP Ð Tech 2 Range 10-105 kPa (0.00-4.97 Volts)Ð
The manifold absolute pressure (MAP) sensor measures
the change in the boost pressure.
MIL Ð Tech 2 Displays ON or OFF Ð
Indicates the ECM commanded state of the malfunction
indicator lamp.
AP Ð Tech 2 Range 0%-100% Ð
AP (Accelerator position) angle is computed by the ECM
from the AP sensor voltage. AP angle should display
ª0%º at idle and ª100%º at wide open throttle.
AP SENSOR Ð Tech 2 Range 0.00-5.00 Volts Ð
The voltage being monitored by the ECM on the AP
sensor signal circuit.
VEHICLE SPEEDÐTech 2 Range 0-255 km/h (0-155
mph)±
The vehicle speed sensor signal is converted into km/h
and mph for display.
Typical Scan Data Values
Use the Typical Scan Data Values Table only after the
On-Board Diagnostic System Check has been
completed, no DTC(s) were noted, and you have
determined that the on-board diagnostics are functioning
properly. Tech 2 values from a properly-running engine
may be used for comparison with the engine you are
diagnosing. The typical scan data values represent
values that would be seen on a normally-running engine.
NOTE: A Tech 2 that displays faulty data should not be
used, and the problem should be reported to the Tech 2
manufacturer. Use of a faulty Tech 2 can result in
misdiagnosis and unnecessary replacement of parts.
Only the parameters listed below are referred to in this
service manual for use in diagnosis. For further
information on using the Tech 2 to diagnose the ECM and
related sensors, refer to the applicable reference section
listed below. If all values are within the typical range
described below, refer to the
Symptoms section for
diagnosis.
Test Conditions
Engine running, lower radiator hose hot, transmission in
park or neutral, accessaries off, brake not applied and air
conditioning off.

6E±100
4JX1±TC ENGINE DRIVEABILITY AND EMISSIONS
DTC P0201 ± Injector # 1 Circuit Fault

StepActionValue(s)Ye sNo
1Was the ªOn-Board Diagnostic (OBD) System Checkº
performed?
ÐGo to Step 2
Go to OBD
System
Check
2Will the engine start?
ÐGo to Step 3
Go to Engine
Cranks But
Will Not Run
chart
31. Install the Tech 2. Clear the DTC.
2. Idle the engine for one minute.
Does DTC P0201 reset?
ÐGo to Step 5Go to Step 4
41. Review the Freeze Frame data with the ignition
ªONº and the engine ªOFFº and note the
parameters.
2. Operate the vehicle within the Freeze Frame
conditions as noted.
Does P0201 reset?
ÐGo to Step 5Ð
5Check the Injector test.
Does the working noise confirm?
ÐGo to Step 6Go to Step 7
61. Install the Tech 2. Clear the DTC.
2. Idle the engine for one minute.
Dose DTC P0201 reset?
ÐVerify repairGo to Step 7
7Check for an open circuit between the injector
connector and the ECM.
Was there an open circuit?
ÐGo to Step 8Go to Step 9
8Repair the open circuit.
Is the action complete?
ÐVerify repairÐ
9Replace the ECM (Refer to the Data Programming in
Case of ECM change).
Is the action complete?
ÐVerify repairGo to Step 10
10Replace the Injector (Refer to the Injector Group Sign
Programming).
Is the action complete?
ÐVerify repairÐ

6E±102
4JX1±TC ENGINE DRIVEABILITY AND EMISSIONS
DTC P0202 ± Injector # 2 Circuit Fault

StepActionValue(s)Ye sNo
1Was the ªOn-Board Diagnostic (OBD) System Checkº
performed?
ÐGo to Step 2
Go to OBD
System
Check
2Will the engine start?
ÐGo to Step 3
Go to Engine
Cranks But
Will Not Run
chart
31. Install the Tech 2. Clear the DTC.
2. Idle the engine for one minute.
Does DTC P0202 reset?
ÐGo to Step 5Go to Step 4
41. Review the Freeze Frame data with the ignition
ªONº and the engine ªOFFº and note the
parameters.
2. Operate the vehicle within the Freeze Frame
conditions as noted.
Does P0202 reset?
ÐGo to Step 5Ð
5Check the Injector test.
Does the working noise confirm?
ÐGo to Step 6Go to Step 7
61. Install the Tech 2. Clear the DTC.
2. Idle the engine for one minute.
Dose DTC P0202 reset?
ÐVerify repairGo to Step 7
7Check for an open circuit between the injector
connector and the ECM.
Was there an open circuit?
ÐGo to Step 8Go to Step 9
8Repair the open circuit.
Is the action complete?
ÐVerify repairÐ
9Replace the ECM (Refer to the Data Programming in
Case of ECM change).
Is the action complete?
ÐVerify repairGo to Step 10
10Replace the Injector (Refer to the Injector Group Sign
Programming).
Is the action complete?
ÐVerify repairÐ

6E±104
4JX1±TC ENGINE DRIVEABILITY AND EMISSIONS
DTC P0203 ± Injector # 3 Circuit Fault

StepActionValue(s)Ye sNo
1Was the ªOn-Board Diagnostic (OBD) System Checkº
performed?
ÐGo to Step 2
Go to OBD
System
Check
2Will the engine start?
ÐGo to Step 3
Go to Engine
Cranks But
Will Not Run
chart
31. Install the Tech 2. Clear the DTC.
2. Idle the engine for one minute.
Does DTC P0203 reset?
ÐGo to Step 5Go to Step 4
41. Review the Freeze Frame data with the ignition
ªONº and the engine ªOFFº and note the
parameters.
2. Operate the vehicle within the Freeze Frame
conditions as noted.
Does P0203 reset?
ÐGo to Step 5Ð
5Check the Injector test.
Does the working noise confirm?
ÐGo to Step 6Go to Step 7
61. Install the Tech 2. Clear the DTC.
2. Idle the engine for one minute.
Dose DTC P0203 reset?
ÐVerify repairGo to Step 7
7Check for an open circuit between the injector
connector and the ECM.
Was there an open circuit?
ÐGo to Step 8Go to Step 9
8Repair the open circuit.
Is the action complete?
ÐVerify repairÐ
9Replace the ECM (Refer to the Data Programming in
Case of ECM change).
Is the action complete?
ÐVerify repairGo to Step 10
10Replace the Injector (Refer to the Injector Group Sign
Programming).
Is the action complete?
ÐVerify repairÐ

6E±106
4JX1±TC ENGINE DRIVEABILITY AND EMISSIONS
DTC P0204 ± Injector #4 Circuit Fault

StepActionValue(s)Ye sNo
1Was the ªOn-Board Diagnostic (OBD) System Checkº
performed?
ÐGo to Step 2
Go to OBD
System
Check
2Will the engine start?
ÐGo to Step 3
Go to Engine
Cranks But
Will Not Run
chart
31. Install the Tech 2. Clear the DTC.
2. Idle the engine for one minute.
Does DTC P0204 reset?
ÐGo to Step 5Go to Step 4
41. Review the Freeze Frame data with the ignition
ªONº and the engine ªOFFº and note the
parameters.
2. Operate the vehicle within the Freeze Frame
conditions as noted.
Does P0204 reset?
ÐGo to Step 5Ð
5Check the Injector test.
Does the working noise confirm?
ÐGo to Step 6Go to Step 7
61. Install the Tech 2. Clear the DTC.
2. Idle the engine for one minute.
Dose DTC P0204 reset?
ÐVerify repairGo to Step 7
7Check for an open circuit between the injector
connector and the ECM.
Was there an open circuit?
ÐGo to Step 8Go to Step 9
8Repair the open circuit.
Is the action complete?
ÐVerify repairÐ
9Is the action complete?ÐVerify repairGo to Step 10
10Replace the Injector (Refer to the Injector Group Sign
Programming).
Is the action complete?
ÐVerify repairÐ