1998 ISUZU TROOPER check engine

6E±35 4JX1±TC ENGINE DRIVEABILITY AND EMISSIONS
Guid to the System

Fuel Injection system is an HEUI (Hydraulically
Actuated, Electronically Controlled, Unit, Injector)
type. In this type of injector system, the oil
pressurized by means of High Pressure Oil Pump
(16) is fed through Rail Pressure Control Valve (10)
and Oil Rail (7) to Injector (29) from which fuel is
injected under this oil pressure.
For diagnosis, therefore, the Rail Pressure as well as
the Electric Circuit must be inspected.
On-Board Diagnostic (OBD) System Check
A Group
060RW135

6E±37 4JX1±TC ENGINE DRIVEABILITY AND EMISSIONS
D Group
060RW134
Circuit Description
The on-board diagnostic system check is the starting
point for any driveability complaint diagnosis. Before
using this procedure, perform a careful visual/physical
check of the ECM and engine grounds for cleanliness and
tightness.
The on-board diagnostic system check is an organized
approach to identifying a problem created by an
electronic engine control system malfunction.
Diagnostic Aids
An intermittent may be caused by a poor connection,
rubbed-through wire insulation or a wire broken inside the
insulation. Check for poor connections or a damaged
harness. Inspect the ECM harness and connector for
improper mating, broken locks, improperly formed or
damaged terminals, poor terminal-to-wire connection,
and damaged harness.
Test Description
Number(s) below refer to the step number(s) on the
Diagnostic Chart:
1. The MIL (ªCheck Engineº lamp) should be ªONº
steady with the ignition ªONº/engine ªOFF.º If not,
Chart A-1 should be used to isolate the malfunction.
2. Checks the Class 2 data circuit and ensures that the
ECM is able to transmit serial data.
3. This test ensures that the ECM is capable of
controlling the MIL (ªCheck Engineº lamp) and the
MIL (ªCheck Engineº lamp) driver circuit is not
shorted to ground.
4. If the engine will not start, the
Cranks But Will Not
Run
chart should be used to diagnose the condition.
7. A Tech 2 parameter which is not within the typical
range may help to isolate the area which is causing
the problem.
9. When the ECM is replaced, the characteristic data of
injector and rail pressure sensor should be inputted.

6E±38
4JX1±TC ENGINE DRIVEABILITY AND EMISSIONS
On- Board Diagnostic (OBD) System Check

StepActionValue(s)Ye sNo
11. Ignition ªON,º engine ªOFF.º
2. Observe the malfunction indicator lamp (MIL or
ªCheck Engineº lamp).
Is the MIL (ªCheck Engineº lamp)ªON?º
ÐGo to Step 2
Go to No MIL
(ªCheck
Engineº lamp)
21. Ignition ªOFF.º
2. Install a Tech 2.
3. Ignition ªON.º
4. Attempt to display ECM engine data with the Tech 2.
Does the Tech 2 display ECM data?
ÐGo to Step 3Go to Step 8
31. Using the Tech 2 output tests function, select MIL
(ªCheck Engineº lamp) dash lamp control and
command the MIL (ªCheck Engineº lamp) ªOFF.º
2. Observe the MIL (ªCheck Engineº lamp).
Did the MIL (ªCheck Engineº lamp) turn ªOFF?º
ÐGo to Step 4
Go to MIL
(ªCheck
Engineº lamp)
On Steady
4Attempt to start the engine.
Did the engine start and continue to run?
ÐGo to Step 5
Go to Cranks
But Will Not
Run
5Select ªDisplay DTCsº with the Tech 2.
Are any DTCs stored?
ÐGo to Step 6Go to Step 7
6Are two or more of the following DTCs stored?
A Group; P0337, P0342, P1193, P1404, P1405,
P1488
B Group; P0337, P0342
C Group; P0112, P0117, P0182, P0197
D Group; P0107, P0405, P1194, P1485
Ð
Go to Chart,
ªMultiple
ECM
Information
Sensor DTCs
Setº
Go to
applicable
DTC table
7Compare ECM data values displayed on the Tech 2 to
the typical engine scan data values.
Are the displayed values normal or close to the typical
values?
ÐGo to Step 8
Refer to
indicated
Component
System
Checks
81. Ignition ªOFF,º disconnect the ECM.
2. Ignition ªON,º engine ªOFF.º
3. Check the Class 2 data circuit for an open, short to
ground, or short to voltage. Also, check the DLC
ignition feed circuit for an open or short to ground
and the DLC ground circuit for an open.
4. If a problem is found, repair as necessary.
Was a problem found?
ÐGo to Step 2Go to Step 9
9Check the Tech 2 on other vehicle.
Was Tech 2 abnormal?
ÐGo to Step 11Go to Step 10
10Replace the ECM (Refer to the Data Programming in
Case of ECM change).
Is the action complete?
ÐGo to Step 2Ð
11Repair the Tech 2 or prepare another Tech 2.
Is the action complete?
ÐGo to Step 2Ð

6E±39 4JX1±TC ENGINE DRIVEABILITY AND EMISSIONS
Engine Control Module ECM
Diagnosis
To read and clear diagnostic trouble codes, use a Tech 2.
IMPORTANT:Use of a Tech 2 is recommended to clear
diagnostic trouble codes from the ECM memory.
Diagnostic trouble codes can also be cleared by turning
the ignition ªOFFº and disconnecting the battery power
from the ECM for 30 seconds. Turning off the ignition and
disconnecting the battery power from the ECM will cause
all diagnostic information in the ECM memory to be
cleared. Therefore, all the diagnostic tests will have to be
re-run.
Since the ECM can have a failure which may affect only
one circuit, following the diagnostic procedures in this
section will determine which circuit has a problem and
where it is.
If a diagnostic chart indicates that the ECM connections
or the ECM is the cause of a problem, and the ECM is
replaced, but this does not correct the problem, one of the
following may be the reason:

There is a problem with the ECM terminal
connections. The terminals may have to be removed
from the connector in order to check them properly.

The problem is intermittent. This means that the
problem is not present at the time the system is being
checked. In this case, refer to the
Symptoms portion
of the manual and make a careful physical inspection
of all components and wiring associated with the
affected system.

There is a shorted solenoid, relay coil, or harness.
Solenoids and relays are turned ªONº and ªOFFº by
the ECM using internal electronic switches called
drivers. A shorted solenoid, relay coil, or harness will
not damage the ECM but will cause the solenoid or
relay to be inoperative.
Multiple ECM Information Sensor
DTCS Set
Circuit Description
The Engine Control Module ECM monitors various
sensors to determine the engine operating conditions.
The ECM controls fuel delivery, spark advance,
transmission operation, and emission control device
operation based on the sensor inputs.
The ECM provides a sensor ground to all of the sensors.
The ECM applies 5 volts through a pull-up resistor, and
determines the status of the following sensors by
monitoring the voltage present between the 5-volt supply
and the resistor:

The fuel temperature (FT) sensor

The engine coolant temperature (ECT) sensor

The Intake air temperature (IAT) sensor
The ECM provides the following sensors with a 5-volt
reference and a sensor ground signal:

The Intake throttle position sensor

The manifold absolute pressure sensor

The rail pressure sensor

The accelerator position sensor

The oil temperature sensor
The camshaft position sensor

The crankshaft position sensor

The EGR pressure sensor
The ECM monitors the signals from these sensors in
order to determine their operating status.
Diagnostic Aids
IMPORTANT:Be sure to inspect ECM and engine
grounds for being secure and clean.
A short to voltage in one of the sensor input circuits may
cause one or more of the following DTCs to be set:

P0337

P0342

P1193

P1404

P1405

P1488
IMPORTANT:If a sensor input circuit has been shorted
to voltage, ensure that the sensor is not damaged. A
damaged sensor will continue to indicate a high or low
voltage after the affected circuit has been repaired. If the
sensor has been damaged, replace it.
An open in the sensor ground circuit between the ECM
and the splice will cause one or more of the following
DTCs to be set:

P0337

P0342

P0117
A short to ground in the 5-volt reference A or B circuit will
cause one or more of the following DTCs to be set:

P0112

P0117

P0182

P0197
An open in the 5-volt reference circuit A, between the
ECM and the splice will cause one or more of the following
DTCs to be set:

P0107

P0405

P1194

P0122
An open in the 5-volt reference circuit B, between the
ECM and the splice will cause one or more of the following
DTCs to be set:

P1485
Check for the following conditions:

Poor connection at ECM. Inspect the harness
connectors for backed-out terminals, improper
mating, broken locks, improperly formed or damage
terminals, and a poor terminal-to-wire connection.

Damaged harness. Inspect the wiring harness for
damage. If the harness is not damaged, observe an
affected sensor's displayed value on the Tech 2 with
the ignition ªONº and the engine ªOFFº while you
move the connectors and the wiring harnesses
related to the following sensors:

ECT Sensor

6E±40
4JX1±TC ENGINE DRIVEABILITY AND EMISSIONS

MAP Sensor

CMP Sensor

CKP Sensor

EGR Pressure Sensor

EGR VSV

RPCV

IAT Sensor
Intake Throttle Motor

Fuel Temperature Sensor

Oil Temperature Sensor

Rail Pressure Sensor
Multiple ECM Information Sensor DTCs Set

StepActionValue(s)Ye sNo
1Was the ªOn-Board Diagnostic (OBD) System Checkº
performed?
ÐGo to Step 2
Go to OBD
System
Check
21. Turn the ignition ªOFF,º disconnect the ECM.
2. Turn the ignition ªON,º check the 5 volt reference D
circuit for the following conditions:

D poor connection at the ECM.

An open between the ECM connector and the
splice.

D short to ground.

D short to voltage.
Is there an open or short?
ÐGo to Step 3Go to Step 4
3Repair the open or short.
Is the action complete?
ÐVerify repairÐ
4Check the sensor ground circuit for the following
conditions:

A poor connection at the ECM or the affected
sensors.

An open between the ECM connector and the
affected sensors.
Is there an open or a poor connection?
ÐGo to Step 5Go to Step 6
5Repair the open or the poor connection.
Is the action complete?
ÐVerify repairGo to Step 6
6Replace the ECM (Refer to the Data Programming in
Case of ECM change).
Is the action complete?
Ð
Go to OBD
System
Check
Ð

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±44
4JX1±TC ENGINE DRIVEABILITY AND EMISSIONS
No Malfunction Indicator Lamp (MIL)
060RW136
Circuit Description
The ªCheck Engineº lamp (MIL) should always be
illuminated and steady with the ignition ªONº and the
engine stopped. Ignition feed voltage is supplied to the
MIL bulb through the meter fuse. The Engine Control
Module ECM turns the MIL ªONº by grounding the MIL
driver circuit.
Diagnostic Aids
An intermittent MIL may be cause by a poor connection,
rubbed-through wire insulation, or a wire broken inside
the insulation. Check for the following items:

Inspect the ECM harness and connections for
improper mating, broken locks, improperly formed or
damaged terminals, poor terminal-to-wire
connection, and damaged harness.

If the engine runs OK, check for a faulty light bulb, an
open in the MIL driver circuit, or an open in the
instrument cluster ignition feed.
If the engine cranks but will not run, check for an open
ECM ignition or battery feed, or a poor ECM to engine
ground.
Test Description
Number(s) below refer to the step number(s) on the
Diagnostic Chart.
2. A ªNo MILº condition accompanied by a no-start
condition suggests a faulty ECM ignition feed or
battery feed circuit.
9. Using a test light connected to B+, probe each of the
ECM ground terminals to ensure that a good ground
is present. Refer to
ECM Terminal End View for
terminal locations of the ECM ground circuits.
12.In this step, temporarily substitute a known good
relay for the ECM relay. The horn relay is nearby,
and it can be verified as ªgoodº simply by honking
the horn. Replace the horn relay after completing
this step.

6E±45 4JX1±TC ENGINE DRIVEABILITY AND EMISSIONS
No Malfunction Indicator Lamp (MIL)

StepActionValue(s)Ye sNo
1Was the ªOn-Board Diagnostic (OBD) System Checkº
performed?
ÐGo to Step 2
Go to OBD
System
Check
2Attempt to start the engine.
Does the engine start?
ÐGo to Step 3Go to Step 6
3Check the meter fuse for the instrument cluster ignition
feed circuit.
Is the fuse OK?
ÐGo to Step 4Go to Step 16
4Ignition ªON,º probe the ignition feed circuit at the
cluster connector with a test light to ground.
Is the test light ªON?º
ÐGo to Step 5Go to Step 13
51. Ignition ªOFF.º
2. Disconnect the ECM.
3. Jumper the MIL driver circuit at the ECM connector
to ground.
4. Ignition ªON.º
Is the MIL ªON?º
ÐGo to Step 10Go to Step 11
6Check the ECM ignition feed and battery feed fuses (15
A engine fuse and 15 A ECM fuse).
Are both fuses OK?
ÐGo to Step 7Go to Step 15
71. Ignition ªOFF.º
2. Disconnect the ECM.
3. Ignition ªON.º
4. Probe the ignition feed circuit at the ECM harness
connector with a test light to ground.
Is the test light ªON?º
ÐGo to Step 8Go to Step 12
8Probe the battery feed circuit at the ECM harness
connector with a test light to ground.
Is the test light ªON?º
ÐGo to Step 9Go to Step 14
9Check for a faulty ECM ground connection.
Was a problem found?
ÐVerify repairGo to Step 10
10Check for damaged terminals at the ECM.
Was a problem found?
ÐVerify repairGo to Step 17
11Check for an open MIL driver circuit between the ECM
and the MIL.
Was a problem found?
ÐVerify repairGo to Step 18
12Substitute a known ªgoodº relay for the ECM main
relay.
Was the malfunction fixed?
ÐVerify repairGo to Step 13
13Repair the open in the ignition feed circuit.
Is the action complete?
ÐVerify repairÐ
14Locate and repair the open ECM battery feed circuit.
Is the action complete?
ÐVerify repairÐ