Isuzu D-Max / Isuzu Rodeo (TFR/TFS). Manual - part 841

6E–93

3.2L ENGINE DRIVEABILITY AND EMISSIONS

Diagnostic Trouble Code (DTC) P0112 (Flash DTC=23) IAT Sensor Circuit Low

Voltage

060RW057

Circuit Description

The intake air temperature (IAT) sensor is a thermistor
which measures the temperature of the air entering the
engine.  The Engine Control Module ECM applies 5 volts
through a pull-up resistor to the IAT sensor.  When the
intake air is cold, the sensor resistance is high and the
ECM will monitor a high signal voltage on the IAT signal
circuit.  If the intake air is warm, the sensor resistance is
lower, causing the ECM to monitor a lower voltage.  DTC
P0112 will set when the ECM detects an excessively low
signal voltage on the intake air temperature sensor signal
circuit.

Conditions for Setting the DTC

D

Ignition SW is ON.

D

IAT signal voltage is under 160m volts.

D

Above conditions present for at least 5 second.

Action Taken When the DTC Sets

D

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

D

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

D

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.

D

A history DTC P0112 will clear after 40 consecutive
warm-up cycles have occurred without a fault.

D

DTC P0112 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:

D

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.

D

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

If DTC P0112 cannot be duplicated, the information
included in the Failure Records data can be useful in
determining vehicle mileage since the DTC was last set.

6E–94

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 P0112 can be repeated only by duplicating

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

Diagnostic Aids.

Intake Air Temperature Sensor

°

C

°

F

OHMS

Temperature vs. Resistance Values

(approximate)

100

212

177

80

176

332

60

140

667

45

113

1188

35

95

1802

25

77

2796

15

59

4450

5

41

7280

–5

23

12300

–15

5

21450

–30

–22

52700

–40

–40

100700

6E–95

3.2L ENGINE DRIVEABILITY AND EMISSIONS

DTC P0112 – IAT Sensor Circuit  Low Voltage

 

Step

Action

Value(s)

Yes

No

1

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

—

Go to 

Step 2

Go to 

OBD

System

Check

2

1. Ignition “ON,” engine “OFF.”
2. Using a Tech 2, monitor the intake air temperature

(IAT).

Is the intake air temperature greater than the specified
value?

148

°

C

(283

°

F)

Go to 

Step 4

Go to 

Step 3

3

1. Ignition “ON,” engine “OFF.”  Review and record

Tech 2 Failure Records data.

2. Operate the vehicle within Failure Records

conditions as noted.

3. Using a Tech 2, monitor the “ DTC” info for DTC

P0112.

Does the Tech 2 indicate DTC P0112 failed this
ignition?

—

Refer to 

Test

Description

Refer to

Diagnostic

Aids

4

1. Ignition “OFF.”
2. Disconnect the IAT sensor electrical connector.
3. Ignition “ON.”
4. Observe the intake air temperature on the Tech 2.

Is the intake air temperature below the specified value?

–38

°

C

(–36

°

F)

Go to 

Step 6

Go to 

Step 5

5

1. Ignition “OFF.”
2. Disconnect the ECM electrical connectors.
3. Check the IAT sensor signal circuit for a short to

ground.

Is the IAT sensor signal circuit shorted to ground?

—

Verify repair

Go to 

Step 7

6

Replace the IAT sensor.

Is the action complete?

—

Verify repair

—

7

Replace the ECM.

Is the action complete?

—

Verify repair

—

6E–96

3.2L ENGINE DRIVEABILITY AND EMISSIONS

Diagnostic Trouble Code (DTC) P0113 (Flash DTC=23) IAT Sensor Circuit High

Voltage

060RW057

Circuit Description

The intake air temperature (IAT) sensor is a thermistor
which measures the temperature of the air entering the
engine. The Engine Control Module ECM applies 5 volts
through a pull-up resistor to the IAT sensor.  When the
intake air is cold, the sensor resistance is high and the
ECM will monitor a high signal voltage on the IAT signal
circuit.  If the intake air is warm, the sensor resistance is
lower causing the ECM to monitor a lower voltage.  DTC
P0113 will set when the ECM detects an excessively high
signal voltage on the intake air temperature sensor signal
circuit.

Conditions for Setting the DTC

D

Ignition SW is ON.

D

The ECT sensor voltage more than 5000m volts.

D

Above conditions present for at least 5 second.

Action Taken When the DTC Sets

D

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

D

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

D

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.

D

A history DTC P0113 will clear after 40 consecutive
warm-up cycles have occurred without a fault.

D

DTC P0113 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:

D

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.

D

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

If DTC P0113 cannot be duplicated, the information
included in the Failure Records data can be useful in
determining vehicle mileage since the DTC was last set.