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Isuzu Trooper (1998-2002 year). Manual - part 604

6E–64

4JX1–TC ENGINE DRIVEABILITY AND EMISSIONS

DTC P0113 –IAT Sensor Circuit High Voltage

(Cont'd)

Step

Yes

Value(s)

Action

1. Ignition “OFF.”
2. Disconnect the ECM, and check the IAT signal

circuit for an open.

3. If the IAT sensor signal circuit is open, repair it as

necessary.

Was the IAT signal circuit open?

—

Verify repair

Go to

Step 9

Check for a poor sensor ground or IAT signal circuit
terminal connection at the ECM and replace
terminal(s) if necessary.

Did any of the terminals need to be replaced?

—

Verify repair

Go to

Step 11

Replace the IAT sensor.

Is the action complete?

—

Verify repair

—

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

Is the action complete?

—

Verify repair

—

6E–65

4JX1–TC ENGINE DRIVEABILITY AND EMISSIONS

Diagnostic Trouble Code (DTC) P0117 (Flash DTC 14)

ECT Sensor Low Voltage

060RW129

Circuit Description

The engine coolant temperature (ECT) sensor is a
thermistor mounted on a coolant crossover pipe at the
rear of the engine. The Engine Control Module ECM
applies a voltage (about 5 volts) through a pull-up resistor
to the ECT signal circuit. When the engine coolant is cold,
the sensor (thermistor) resistance is high, therefore the
ECM will measure a high signal voltage. As the engine
coolant warms, the sensor resistance becomes lower,
and the ECT signal voltage measured at the ECM drops.

Action Taken When the DTC Sets

The ECM will store conditions which were present
when the DTC was set as Freeze Frame and in the
Failure Records data.

Conditions for Clearing the MIL/DTC

DTC P0117 can be cleared by using the Tech 2 “Clear
Info” function or by disconnecting the ECM battery
feed.

Diagnostic Aids

Check for the following conditions:

Poor connection at ECM – Inspect harness connectors
for backed-out terminals, improper mating, broken

locks, improperly formed or damaged terminals, and
poor terminal-to-wire connection.

Damaged harness – Inspect the wiring harness for
damage. If the harness appears to be OK, observe the
ECT display on the Tech 2 while moving connectors
and wiring harnesses related to the ECT sensor. A
change in the ECT display will indicate the location of
the fault.

If DTC P0117 cannot be duplicated, the information
included in the Failure Records data can be useful in
determining vehicle mileage since the DTC was last set.
If it is determined that the DTC occurs intermittently.

Test Description

Number(s) below refer to the step number(s) on the
Diagnostic Chart.
2. Verifies that the fault is present.

3. If DTC P0117 can be repeated only by duplicating

the Failure Records conditions, refer to the
“Temperature vs. Resistance Values” table. The
table may be used to test the ECT sensor at various
temperatures to evaluate the possibility of a
“shifted” sensor that may be shorted above or below
a certain temperature. If this is the case, replace
the ECT sensor. If the ECT sensor appears to be
OK, the fault is intermittent; refer to

Diagnostic Aids.

6E–66

4JX1–TC ENGINE DRIVEABILITY AND EMISSIONS

Engine Coolant Temperature Sensor

Ohms

Temperature vs. Resistance Values

(approximate)

2796

4450

DTC P0117 – ECT Sensor Low Voltage

Step

Action

Value(s)

Yes

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

—

Go to

Step 2

Go to

OBD

System

Check

1. Ignition “ON,” engine “OFF.”
2. Observe the “Eng Cool Temp” display on the Tech 2.

Is the “Eng Cool Temp” below the specified value?

139

(282

Go to

Step 4

Go to

Step 3

1. Ignition “ON,” engine “OFF.”
2. Review and record Tech 2 Failure Records data.
3. Operate the vehicle within Failure Records

conditions as noted.

4. Using a Tech 2, monitor “ DTC” info for DTC P0117.

Does the Tech 2 indicate DTC P0117 failed this
ignition?

—

Go to

Step 4

Refer to

Diagnostic

Aids

1. Disconnect the ECT sensor electrical connector.
2. Observe the “Eng Cool Temp” display on the Tech 2.

Is the “Eng Cool Temp” at the specified value?

–39

(–38

Go to

Step 6

Go to

Step 5

1. Ignition “OFF.”
2. Disconnect the ECM and check the ECT signal

circuit for a short to ground or a short to the sensor
ground circuit.

3. If the ECT signal circuit is shorted. repair it as

necessary.

Was the ECT signal circuit shorted to ground?

—

Verify repair

Go to

Step 7

Replace the ECT sensor.

Is the action complete?

—

Verify repair

—

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

Is the action complete?

—

Verify repair

—

6E–67

4JX1–TC ENGINE DRIVEABILITY AND EMISSIONS

Diagnostic Trouble Code (DTC) P0118 (Flash DTC 14)

ECT Sensor High Voltage

060RW129

Circuit Description

The engine coolant temperature (ECT) sensor is a
thermistor mounted in on a coolant crossover pipe at the
rear of the engine. The Engine Control Module ECM
applies a voltage (about 5 volts) through a pull-up resistor
to the ECT signal circuit. When the engine coolant is cold,
the sensor (thermistor) resistance is high, therefore the
ECM will measure a high signal voltage. As the engine
coolant warms, the sensor resistance becomes less, and
the ECT signal voltage measured at the ECM drops.

Action Taken When the DTC Sets

The ECM will store conditions which were present
when the DTC was set as Freeze Frame and in the
Failure Records data.

Conditions for Clearing the MIL/DTC

DTC P0118 can be cleared by using the Tech 2 “Clear
Info” function or by disconnecting the ECM battery
feed.

Diagnostic Aids

Check for the following conditions:

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

If DTC P0118 cannot be duplicated, the information
included in the Failure Records data can be useful in
determining vehicle mileage since the DTC was last set.

Content .. 602 603 604 605 ..