Isuzu D-Max / Isuzu Rodeo (TFR/TFS). Manual - part 843

6E–101

3.2L ENGINE DRIVEABILITY AND EMISSIONS

Diagnostic Trouble Code (DTC) P0118 (Flash DTC=14) ECT Sensor Circuit High

Voltage

060RW072

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. With
a fully warmed-up engine, the ECT signal voltage should
measure about 1.5 to 2.0 volts.

Conditions for Setting the DTC

Ignition SW is ON.

The ECT sensor voltage more than 5000m volts.

Above conditions present for at least 5 second.

Action Taken When the DTC Sets

The ECM will illuminate the malfunction indicator lamp
(MIL) the first time the fault is detected.

The ECM will substitute the ECT reading with a default
engine coolant temperature value. The default value
is based on start-up intake air temperature and running
time.

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

The ECM will turn the MIL “OFF” on the third
consecutive trip cycle during which the diagnostic has
been run and the fault condition is no longer present.

A history DTC P0118 will clear after 40 consecutive
warm-up cycles have occurred without a fault.

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.

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 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.
If it is determined that the DTC occurs intermittently,
performing the DTC P1115 Diagnostic Chart may isolate
the cause of the fault.

6E–102 3.2L ENGINE DRIVEABILITY AND EMISSIONS

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 P0118 can be repeated only by duplicating

the Failure Records conditions, refer to the
“Temperature vs. Resistance Value” 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.

Engine Coolant Temperature Sensor

OHMS

Temperature vs. Resistance Values

(approximate)

100

212

177

176

332

140

667

113

1188

1802

2796

4450

7280

–5

12300

–15

21450

–30

–22

52700

–40

100700

6E–103

3.2L ENGINE DRIVEABILITY AND EMISSIONS

DTC P0118 – ECT Sensor Circuit High 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?

–39

(–38

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 the “ DTC” info for DTC

P0118.

Does the Tech 2 indicate DTC P0118 failed?

—

Refer to

Test

Description

Refer to

Diagnostic

Aids

1. Disconnect the ECT sensor electrical connector.
2. Jumper the ECT signal circuit and the sensor

ground circuit together at the ECT sensor harness
connector.

3. Observe the “Eng Cool Temp” display on the Tech 2.

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

140

(284

Go to

Step 6

Go to

Step 5

1. Jumper the ECT signal circuit at the ECT sensor

harness connector to chassis ground.

2. Observe the “Eng Cool Temp” display on the Tech 2.

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

140

(284

Go to

Step 7

Go to

Step 8

Check for poor connections at the ECT sensor and
replace terminals if necessary.

Did any terminals require replacement?

—

Verify repair

Go to

Step 10

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

ground circuit for an open.

3. If the ECT sensor ground circuit is open, repair it as

necessary.

Was the ECT sensor ground circuit open?

—

Verify repair

Go to

Step 9

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

circuit for an open.

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

necessary.

Was the ECT signal circuit open?

—

Verify repair

Go to

Step 9

Check for a poor sensor ground or ECT 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 ECT sensor.

Is the action complete?

—

Verify repair

—

Replace the ECM.

Is the action complete?

—

Verify repair

—

6E–104 3.2L ENGINE DRIVEABILITY AND EMISSIONS

Diagnostic Trouble Code (DTC) P0121 (Flash DTC=21) TP System Performance

060RW077

Circuit Description

The throttle position (TP) sensor circuit provides a voltage
signal that changes relative to throttle blade angle. The
signal voltage will vary from about 0.6 volts at closed
throttle to about 4.5 volts at wide open throttle (WOT).
The TP signal is one of the most important inputs used by
the Engine Control Module ECM for fuel control and many
of the ECM-controlled outputs. The ECM monitors
throttle position and compares actual throttle position
from the TP sensor to a predicted TP value calculated
from engine speed. If the ECM detects an out-of-range
condition, DTC P0121 will set.

Conditions for Setting the DTC

The engine is running.

No BARO/ECT/MAF/CKP/CMP DTCs, or P0122,
P0123 DTCs are set.

BARO reading is below 3000m volts.

Throttle is steady, throttle angle is changing less than
1%.

ECT reading more than 75

Above conditions present for at least second.

Action Taken When the DTC Sets

The ECM will illuminate the malfunction indicator lamp
(MIL) after the second consecutive trip in which the
fault is detected.

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

The ECM will use a default throttle position based on
mass air flow and RPM.

Conditions for Clearing the MIL/DTC

The ECM will turn the MIL “OFF” on the third
consecutive trip cycle during which the diagnostic has
been run and the fault condition is no longer present.

A history DTC P0121 will clear after 40 consecutive
warm-up cycles have occurred without a fault.

DTC P0121 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:

Skewed BARO signal or faulty BARO sensor – An
incorrect BARO signal may cause the ECM to
incorrectly calculate the predicted TP sensor value
during high engine load situations. Check for an
unusually low BARO reading. This condition can
cause DTC P0121 to be set.

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

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