Isuzu Trooper (1998-2002 year). Manual - part 597

6E–36

4JX1–TC ENGINE DRIVEABILITY AND EMISSIONS

B Group

060RW133

C Group

060RW129

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 (“Check Engine” lamp) should be “ON”

steady with the ignition “ON”/engine “OFF.”  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 (“Check Engine” lamp) and the
MIL (“Check Engine” 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

 

Step

Action

Value(s)

Yes

No

1

1. Ignition “ON,” engine “OFF.”
2. Observe the malfunction indicator lamp (MIL or

“Check Engine” lamp). 

Is the MIL (“Check Engine” lamp)“ON?”

—

Go to 

Step 2

Go to 

No MIL

(“Check

Engine” lamp)

2

1. Ignition “OFF.”
2. Install a Tech 2.
3. Ignition “ON.”
4. Attempt to display ECM engine data with the Tech 2.

Does the Tech 2 display ECM data?

—

Go to 

Step 3

Go to 

Step 8

3

1. Using the Tech 2 output tests function, select MIL

(“Check Engine” lamp) dash lamp control and
command the MIL (“Check Engine” lamp) “OFF.”

2. Observe the MIL (“Check Engine” lamp).

Did the MIL (“Check Engine” lamp) turn “OFF?”

—

Go to 

Step 4

Go to 

MIL

(“Check

Engine” lamp)

On Steady

4

Attempt to start the engine.

Did the engine start and continue to run?

—

Go to 

Step 5

Go to 

Cranks

But Will Not

Run

5

Select “Display DTCs” with the Tech 2.

Are any DTCs stored?

—

Go to 

Step 6

Go to 

Step 7

6

Are 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

—

Go to 

Chart,

“Multiple

ECM

Information

Sensor DTCs

Set”

Go to

applicable
DTC table

7

Compare 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?

—

Go to 

Step 8

Refer to

indicated

Component

System
Checks

8

1. Ignition “OFF,” disconnect the ECM.
2. Ignition “ON,” engine “OFF.”
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?

—

Go to 

Step 2

Go to 

Step 9

9

Check the Tech 2 on other vehicle.

Was Tech 2 abnormal?

—

Go to 

Step 11

Go to 

Step 10

10

Replace the ECM (Refer to the Data Programming in
Case of ECM change).

Is the action complete?

—

Go to 

Step 2

—

11

Repair the Tech 2 or prepare another Tech 2.

Is the action complete?

—

Go to 

Step 2

—

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 “OFF” 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:

D

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.

D

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.

D

There is a shorted solenoid, relay coil, or harness.
Solenoids and relays are turned “ON” and “OFF” 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:

D

The fuel temperature (FT) sensor

D

The engine coolant temperature (ECT) sensor

D

The Intake air temperature (IAT) sensor

The ECM provides the following sensors with a 5-volt
reference and a sensor ground signal:

D

The Intake throttle position sensor

D

The manifold absolute pressure sensor

D

The rail pressure sensor

D

The accelerator position sensor

D

The oil temperature sensor

D

The camshaft position sensor

D

The crankshaft position sensor

D

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:

D

P0337

D

P0342

D

P1193

D

P1404

D

P1405

D

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:

D

P0337

D

P0342

D

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:

D

P0112

D

P0117

D

P0182

D

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:

D

P0107

D

P0405

D

P1194

D

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:

D

P1485

Check for the following conditions:

D

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.

D

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 “ON” and the engine “OFF” while you
move the connectors and the wiring harnesses
related to the following sensors:

D

ECT Sensor