Opel Frontera UBS. Manual - part 1188

6E–118

ENGINE DRIVEABILITY AND EMISSIONS

Diagnostic Trouble Code (DTC) P0112 IAT Sensor Circuit Low Voltage

D06RW026

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 is
lower, causing the PCM to monitor a lower voltage.  DTC
P0112 will set when the PCM detects an excessively low
signal voltage on the intake air temperature sensor signal
circuit.

Conditions for Setting the DTC

D

The engine has been running for over 2 minutes.

D

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

D

IAT signal voltage indicates and intake air temperature
greater than 148

°

C (298

°

F) (about 5 volts) for a total

of 12.5 seconds over a 25-second period of time.

Action Taken When the DTC Sets

D

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

D

The PCM 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

DTC P0112 can be cleared by using the Tech 2 “Clear
Info” function or by disconnecting the PCM battery
feed.

Diagnostic Aids

Check for the following conditions:

D

Poor connection at PCM – Inspect harness connectors
for backed-bout 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.

Test Description

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

6E–119

ENGINE DRIVEABILITY AND EMISSIONS

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–120

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 “Specific 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 PCM 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 PCM.

IMPORTANT: The replacement PCM must be
programmed.  Refer to 

UBS 98model year Immobilizer

Workshop Manual.

Is the action complete?

—

Verify repair

—

6E–121

ENGINE DRIVEABILITY AND EMISSIONS

Diagnostic Trouble Code (DTC) P0113 IAT Sensor Circuit High Voltage

D06RW026

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 is
lower causing the PCM to monitor a lower voltage.  DTC
P0113 will set when the PCM detects an excessively high
signal voltage on the intake air temperature sensor signal
circuit.

Conditions for Setting the DTC

D

The engine has been running for over 4 minutes.

D

Vehicle speed is less than  20 mph (32 km/h). 

D

ECT signal temperature is above 60

°

C (140

°

F).

D

Mass air flow is less then 20 g/second.

D

IAT signal voltage indicates an intake air temperature
less than –39

°

C (–38

°

F) for total of 12.5 seconds over

a 25-second period.

Action Taken When the DTC Sets

D

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

D

The PCM 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

DTC P0113 can be cleared by using the Tech 2 “Clear
Info” function or by disconnecting the PCM battery
feed.

Diagnostic Aids

Check for the following conditions:

D

The  IAT sensor shares a ground with the EGR position
sensor and the TP sensor.  Check the ground if these
DTC’s are set.

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.  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.

Test Description

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