Isuzu Amigo / Axiom / Trooper / Rodeo / VehiCross. Manual - part 1312

6E1–324

RODEO Y22SE 2.2L ENGINE DRIVEABILITY AND EMISSION

DIAGNOSTIC TROUBLE CODE (DTC) P1112 INTAKE AIR TEMPERATURE (IAT)

SENSOR CIRCUIT INTERMITTENT LOW VOLTAGE

060R100027

Circuit Description

The intake air temperature (IAT) sensor is a thermistor
which measures the temperature of the air entering the
engine. The powertrain control module (PCM) 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
PCM will monitor a high signal voltage on the IAT signal
circuit. If the intake air is warm, the sensor resistance
becomes lower, causing the PCM to monitor a lower
voltage. Diagnostic Trouble Code P1112 will set when the
PCM intermittently detects an excessively low signal
voltage on the intake air temperature sensor signal
circuit.  DTC P1112 is a type D code.

Conditions for Setting the DTC

D

The engine has been running for over 2 minutes.

D

Vehicle speed is greater than 48 km/h (30 mph).

D

IAT signal voltage is greater than 148

°

C (298

°

F)

(about 0.10 volt). The above conditions are met for 20
test failures within 200 test samples.

Action Taken When the DTC Sets

D

The PCM will not illuminate the malfunction indicator
lamp (MIL).

D

The PCM will store conditions which were present
when the Diagnostic Trouble Code set as Failure

Records data only. This information will not be stored
as Freeze Frame data.

D

The PCM will substitute a default value for intake air
temperature.

Conditions for Clearing the DTC

D

A history Diagnostic Trouble Code P1112 will clear
after 40 consecutive warm–up cycles have occurred
without a fault.

D

Diagnostic Trouble Code P1112 can be cleared by
using the Scan Tool’s ”Clear Info” function.

Diagnostic Aids

Check for the following conditions:

D

Poor connection at PCM – 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; shorts to ground, shorts to battery positive,
and open circuits. 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.

Reviewing the Failure Records vehicle mileage since the
diagnostic test last failed may help determine how often
the condition that caused the Diagnostic Trouble Code to

6E1–325

RODEO Y22SE 2.2L ENGINE DRIVEABILITY AND EMISSION

be set occurs. This may assist in diagnosing the
condition.

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 P1112 can be repeated only by duplicating

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

The chart may be used to test the IAT 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
IAT sensor.

Intake Air Temperature Sensor

°

C

°

F

W

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

DTC P1112 – IAT Sensor Circuit Intermittent 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

Is DTC P0112 also set?

—

Go to DTC

P0112 chart

first 

Go to Step  3 

3

1. Check the IAT signal circuit between the IAT sensor

connector and the PCM for an intermittent short to
ground.

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

Was a problem found?

—

Verify repair

Refer to

Diagnostic

Aids 

6E1–326

RODEO Y22SE 2.2L ENGINE DRIVEABILITY AND EMISSION

DIAGNOSTIC TROUBLE CODE (DTC) P1114 ENGINE COOLANT 

TEMPERATURE (ECT) SENSOR CIRCUIT INTERMITTENT LOW VOLTAGE

060R100028

Circuit Description

The engine coolant temperature (ECT) sensor is a
thermistor mounted in the engine coolant stream. The
powertrain control module (PCM) applies a voltage
(about 5.0 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 PCM will
measure a high signal voltage. As the engine coolant
warms, the sensor resistance becomes less, and the
ECT signal voltage measured at the PCM drops. With a
fully warmed up engine, the ECT signal voltage should
measure about 1.5 to 2.0 volts. If the PCM detects an
ECT signal that is intermittently below the range of the
ECT sensor, Diagnostic Trouble Code P1114 will set.
DTC P1114 is a type D code.

Conditions for Setting the DTC

D

Engine run time longer than 2 minutes.

D

The ECT sensor signal is intermittently greater than
150

°

C (302

°

F) (about 0.10 volt). The above conditions

are met for 20 test failures within 200 test samples.

Action Taken When the DTC Sets

D

The PCM will not illuminate the malfunction indicator
lamp (MIL).

D

The PCM will store conditions which were present
when the Diagnostic Trouble Code set as Failure

Records data only. This information will not be stored
as Freeze Frame data.

Conditions for Clearing the DTC

D

A history Diagnostic Trouble Code P1114 will clear
after 40 consecutive warm–up cycles have occurred
without a fault.

D

Diagnostic Trouble Code P1114 can be cleared by
using the Scan Tool’s ”Clear Info” function.

Diagnostic Aids

Check for the following conditions:

D

Poor connection at PCM – 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; shorts to ground, shorts to battery positive,
and open circuits. 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.

Reviewing the Failure Records vehicle mileage since the
diagnostic test last failed may help determine how often
the condition that caused the Diagnostic Trouble Code to
be set occurs. This may assist in diagnosing the
condition.

6E1–327

RODEO Y22SE 2.2L ENGINE DRIVEABILITY AND EMISSION

Engine Coolant Temperature Sensor

°

C

°

F

W

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

DTC P1114 – ECT Sensor Circuit Intermittent 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

Is DTC P0117 also set?

—

Go to DTC

P0117 first 

Go to Step  3 

3

1. Check the ECT signal circuit between the ECT

sensor connector and the PCM for an intermittent
short to ground.

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

Was a problem found?

—

Verify repair

Refer to

Diagnostic

Aids