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Isuzu Trooper (1998-2002 year). Manual - part 632

6E–176

4JX1–TC ENGINE DRIVEABILITY AND EMISSIONS

Symptom Diagnosis

Preliminary Checks

Before using this section, perform the “On–Board
Diagnostic (OBD) System Check” and verify all of the
following items:

The powertrain control module (ECM) and
malfunction indicator lamp (MIL) (CHECK ENGINE
lamp) are operating correctly.

There are no DTC(s) stored.

Tech–2 data is within normal operating range. Refer
to

Typical Scan Data Values.

Verify the customer complaint and locate the correct
symptom in the table of contents. Perform the
procedure included in the symptom chart.

Visual/Physical Check

Several of the symptom procedures call for a careful
visual/physical check. This can lead to correcting a
problem without further checks and can save valuable
time.
This check should include the following items:

ECM grounds for cleanliness, tightness and proper
location.

Vacuum hoses for splits, kinks, and proper
connections, as shown on the “Vehicle Emission
Control Information” label. Check thoroughly for any
type of leak or restriction.

Air intake ducts for collapsed or damaged areas.

Injector wires for cracking, hardness, and carbon
tracking.

Wiring for proper connections, pinches and cuts.

Intermittents

IMPORTANT:

An intermittent problem may or may not

turn on the malfunction indicator lamp (MIL) or store a
DTC. DO NOT use the Diagnostic Trouble Code (DTC)
charts for intermittent problems. The fault must be
present to locate the problem.
Most intermittent problems are caused by faulty electrical
connections or wiring. Perform a careful visual/physical
check for the following conditions:

Poor mating of the connector halves or a terminal not
fully seated in the connector (backed out).

Improperly formed or damaged terminal.

All connector terminals in the problem circuit should
be carefully checked for proper contact tension.

Poor terminal–to–wire connection. This requires
removing the terminal from the connector body to
check.

Road test the vehicle with a Digital Multimeter
(5-8840-0285-0) connected to a suspected circuit. An
abnormal voltage when the malfunction occurs is a good
indication that there is a fault in the circuit being
monitored.
Use a scan tool to help detect intermittent conditions. The
scan tools have several features that can be used to
locate an intermittent condition. Use the following feature
to find intermittent faults:

Using a Tech–2 “Freeze Frame” buffer or “Failure
Records” buffer can aid in locating an intermittent
condition. Review and record the information in the
freeze frame or failure record associated with the
intermittent DTC being diagnosed. The vehicle can
be driven within the conditions that were present
when the DTC originally set.

To check for loss of diagnostic code memory, disconnect
the MAP sensor and idle the engine until the MIL (CHECK
ENGINE lamp) comes on. DTC P0107 should be stored
and kept in memory when the ignition is turned “OFF.” If
not, the ECM is faulty. When this test is completed, make
sure that you clear the DTC P0107 from memory.
An intermittent MIL (CHECK ENGINE lamp) with no
stored DTC may be caused by the following:

MIL (CHECK ENGINE lamp) wire to ECM shorted to
ground.

Poor ECM grounds. Refer to the ECM wiring
diagrams.

Check for improper installation of electrical options such
as lights, cellular phones, etc.
Check for an open diode across the A/C compressor
clutch and check for other open diodes (refer to wiring
diagrams in

Electrical Diagnosis).

If problem has not been found, refer to

ECM Connector

Symptom tables.

6E–177

4JX1–TC ENGINE DRIVEABILITY AND EMISSIONS

Hard Start Symptom

Step

Action

Value(s)

Yes

DEFINITION:
Engine cranks, but does not start for a long time. Does
eventually run, or may start but immediately stalls.

Was the “On-Board Diagnostic (OBD) System Check”
performed?

—

Go to

Step 2

Go to

OBD

System

Check

1. Perform a bulletin search.
2. If a bulletin that addresses the symptom is found,

correct the condition as instructed in the bulletin.

Was a bulletin found that addresses the symptom?

—

Verify repair

Go to

Step 3

Was a visual/physical check performed?

—

Go to

Step 4

Go to

Visual/Physic

al Check

Check engine coolant temperature (ECT) sensor for
shift in value. After 8 hours with the hood up and the
engine not running, connect the scan tool. With the
ignition “ON” and the engine not running, compare
engine coolant temperature to manifold air
temperature.

Are ECT and MAT within the specified value of each
other?

C (

Go to

Step 8

Go to

Step 5

1. Using Tech–2, display the engine coolant

temperature and note the value.

2. Check the resistance of the engine coolant

temperature sensor.

3. Refer to

Engine Coolant Temperature Sensor

Temperature vs. Resistance chart on DTC P0118
Diagnostic Support for resistance specifications.

Is the resistance value near the resistance for the
temperature noted?

—

Go to

Step 7

Go to

Step 6

Replace the ECT sensor.

Is the action complete?

—

Verify repair

—

Locate and repair high resistance or poor connection in
the ECT signal circuit or the ECT sensor ground.

Is the action complete?

—

Verify repair

—

1. Injector Test

Operate the each injector by Tech 2 with the
ignition “ON” and check if the working noise
confirm.

2. If a problem is found, check the harness or replace

the injector.

Is the action complete?

—

Verify repair

Go to

Step 9

Check the oil rail pressure by Tech 2 at the cranking.

Is the pressure near the specified value?

Less than 3

MPa

Go to

Step 10

Go to

Step 11

Check the oil leakage on the high oil pressure line.
If the oil leakage is found, repair as necessary.

Was the oil leakage found?

—

Verify repair

Go to

Step 11

1. Check for water-or alcohol-contaminated fuel.
2. If a problem is found, repair as necessary.

Was a problem found?

—

Verify repair

Go to

Step 12

6E–178

4JX1–TC ENGINE DRIVEABILITY AND EMISSIONS

Hard Start Symptom

(Cont'd)

Step

Yes

Value(s)

Action

1. Check the battery voltage.
2. If a problem is found, repair as necessary.

Was a problem found?

—

Verify repair

Go to

Step 13

1. Check for the following engine mechanical

problems (Refer to

Engine Mechanical):

Low compression

Leaking cylinder head gaskets

Worn or incorrect camshaft

Camshaft drive belt slipped or stripped

2. If a problem is found, repair as necessary.

Was a problem found?

—

Verify repair

Go to

Step 14

1. Review all diagnostic procedures within this table.
2. If all procedures have been completed and no

malfunctions have been found, review/inspect the
following:

Visual/physical inspection

Tech–2 data

Freeze Frame data/Failure Records buffer

All electrical connections within a suspected
circuit and/or system.

3. If a problem is found, repair as necessary.

Was a problem found?

—

Verify repair

Contact

Technical

Assistance

6E–179

4JX1–TC ENGINE DRIVEABILITY AND EMISSIONS

Surges and/or Chuggles Symptom

Step

Action

Value(s)

Yes

DEFINITION:
Engine power variation under steady throttle or cruise.
Feels like the vehicle speeds up and slows down with
no change in the accelerator pedal.

Was the “On-Board Diagnostic (OBD) System Check”
performed?

—

Go to

Step 2

Go to

OBD

System

Check

1. Perform a bulletin search.
2. If a bulletin that addresses the symptom is found,

correct the condition as instructed in the bulletin.

Was a bulletin found that addresses the symptom?

—

Verify repair

Go to

Step 3

Was a visual/physical check performed?

—

Go to

Step 4

Go to

Visual/

Physical

Check

Be sure that the driver understands transmission
torque converter clutch and A/C compressor operation
as explained in the owner’s manual.
Inform the customer how the TCC and the A/C clutch
operate.

Is the customer experiencing a normal condition?

—

System OK

Go to

Step 5

1. Check the priming pump. Refer to

Fuel System.

2. If a problem is found, operate the priming pump.

Was a problem found?

—

Verify repair

Go to

Step 6

1. Injector Test

Operate the each injector by Tech 2 with the
ignition “ON” and check if the working noise
confirm.

2. If a problem is found, check the harness and repair

as necessary.

Is the action complete?

—

Verify repair

Go to

Step 7

1. Check ECM grounds for the cleanliness, tightness

and proper locations. Refer to the ECM wiring
diagrams in

Electrical Diagnosis.

2. If a problem is found, repair as necessary.

Was a problem found?

—

Verify repair

Go to

Step 8

1. Check AP sensor connections.
2. If a problem is found, replace the faulty terminals as

necessary. Refer to

Electrical Diagnosis for wiring

repair procedures.

Was a problem found?

—

Verify repair

Go to

Step 9

1. Visually/physically check vacuum hoses for splits,

kinks, and proper connections and routing as
shown on the “Vehicle Emission Control
Information” label.

2. If a problem is found, repair as necessary.

Was a problem found?

—

Verify repair

Go to

Step 10

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