Buick Regal: DTC P0112, P0113, or P0114

Diagnostic Instructions

• Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
• Review Strategy Based Diagnosis for an overview of the diagnostic approach.
• Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptors

DTC P0112

Intake Air Temperature (IAT) Sensor 1 Circuit Low Voltage

DTC P0113

Intake Air Temperature (IAT) Sensor 1 Circuit High Voltage

DTC P0114

Intake Air Temperature (IAT) Sensor 1 Circuit Intermittent

Diagnostic Fault Information

IAT Sensor 1

Typical Scan Tool Data

IAT Sensor 1

Circuit/System Description

The intake air temperature (IAT) sensor 1 is a variable resistor that measures the temperature of the air in the sensor bore. The engine control module (ECM) supplies 5 V to the IAT sensor 1 signal circuit and a ground for the IAT sensor 1 low reference circuit. The signal varies with inlet air temperature and is displayed by the scan tool as ºC (ºF).

The multifunction intake air sensor houses the following:

• IAT sensor 1
• IAT sensor 2
• Humidity sensor
• Mass Air Flow (MAF) sensor
• BARO pressure sensor

IAT Sensor 1 - Temperature, Resistance, Voltage Table

Conditions for Running the DTCs

P0112, P0113, and P0114

• The ignition is ON, or the engine is running.
• The DTCs run continuously when the above conditions are met.

Conditions for Setting the DTC

NOTE: The scan tool display range is between -40 and +150ºC (-40 and +302ºF).

P0112

The ECM detects that the IAT sensor signal is warmer than 149ºC (300ºF) for at least 5 s.

P0113

The ECM detects that the IAT sensor signal is colder than -60ºC (-76ºF) for at least 5 s.

P0114

Where this DTC is used, the ECM detects that the IAT sensor signal is intermittent or has abruptly changed for at least 5 s.

Action Taken When the DTCs Set

• DTCs P0112, P0113, and P0114 are Type B DTCs.
• The ECM commands the cooling fans ON.

Conditions for Clearing the DTCs

DTCs P0112, P0113, and P0114 are Type B DTCs.

Diagnostic Aids

With the ignition ON, the engine OFF, if the engine is cold, a properly functioning IAT sensor 1 will gradually increase the scan tool IAT Sensor 1 parameter. This is due to the heat that is generated by the MAF sensor heating elements.

Reference Information

Schematic Reference

Engine Controls Wiring Schematics (LTG)

Connector End View Reference

Component Connector End View Index

Electrical Information Reference

• Circuit Testing
• Connector Repairs
• Testing for Intermittent Conditions and Poor Connections
• Wiring Repairs

Powertrain Component Views

Powertrain Component Views

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification

NOTE: To minimize the effects of residual engine heat and sensor internal heating elements, perform Steps 1 and 2 of this verification procedure only if the ignition has been OFF for 8 hours or more.

1. Ignition ON.

2. Verify the following scan tool parameters are within 30ºC (54ºF) of each other.

• Start-Up IAT Sensor 1
• IAT Sensor 2
• IAT Sensor 3; where equipped
• If not within 30ºC (54ºF)

Refer to Circuit/System Testing.

• Go to next step: If within 30ºC (54ºF)

3. Engine idling, verify the following scan tool parameters are between: -38 and +149ºC (-36 and +300ºF).

• IAT Sensor 1
• IAT Sensor 2
• IAT Sensor 3; where equipped
• If not between: -38 and +149ºC (-36 and +300ºF)

Refer to Circuit/System Testing.

• Go to next step: If between: -38 and +149ºC (-36 and +300ºF)

4. Operate the vehicle within the conditions for running the DTC. You may also operate the vehicle within the conditions that you observed from the freeze frame/failure records data.

5. Verify the DTC does not set.

• If the DTC sets

Refer to Circuit/System Testing.

• Go to next step: If the DTC does not set

6. All OK

Circuit/System Testing

NOTE: You must perform the Circuit/System Verification before proceeding with Circuit/System Testing.

1. Ignition OFF, and all vehicle systems OFF, it may take up to 2 min. for all vehicle systems to power down. Disconnect the harness connector at the B75C Multifunction Intake Air sensor.

2. Test for less than 5 Ω between the low reference circuit terminal 3 and ground.

• If 5 Ω or greater

1. Ignition OFF, disconnect the harness connector at the K20 engine control module.
2. Test for less than 2 Ω in the low reference circuit end to end.
   • If 2 Ω or greater, repair the open or high resistance in the circuit.
   • If less than 2 Ω replace the K20 engine control module.

• Go to next step: If less than 5 Ω

3. Ignition ON, test for 4.8 - 5.2 V between the intake air temperature sensor 1 signal circuit terminal 1 and ground.

• If less than 4.8 V

1. Ignition OFF, disconnect the harness connector at the K20 engine control module.
2. Test for infinite resistance between the signal circuit and ground.
   • If less than infinite resistance, repair the short to ground on the circuit.
   • Go to next step: If infinite resistance
3. Test for less than 2 Ω in the signal circuit end to end.
   • If 2 Ω or greater, repair the open/high resistance in the circuit.
   • If less than 2 Ω, replace the K20 engine control module.

• If greater than 5.2 V

NOTE: If the signal circuit is shorted to a voltage the engine control module or the sensor may be damaged.

1. Ignition OFF, disconnect the harness connector at the K20 engine control module.
2. Ignition ON, test for less than 1 V between the signal circuit and ground.
   • If 1 V or greater, repair the short to voltage on the circuit.
   • If less than 1 V, replace the K20 engine control module.

• Go to next step: If between 4.8 - 5.2 V

4. Ignition ON, verify the scan tool IAT Sensor 1 parameter is colder than -39ºC (-38ºF).

• If warmer than -39ºC (-38ºF).

1. Ignition OFF, disconnect the harness connector at the K20 Engine Control Module.
2. Test for infinite resistance between the signal circuit terminal 1 and ground.
   • If less than infinite resistance, repair the short to ground on the circuit.
   • Go to next step: If infinite resistance
3. Test for less than 2 Ω in the signal circuit end to end.
   • If 2 Ω or greater, repair the open/high resistance in the circuit.
   • If less than 2 Ω, replace the K20 Engine Control Modul

• Go to next step: If colder than -39ºC (-38ºF).

5. Ignition OFF, install a 3 A fused jumper wire between the signal circuit terminal 1 and the low reference circuit terminal 3.

6. Verify the scan tool IAT Sensor 1 parameter is warmer than 148ºC (298ºF).

• If colder than 148ºC (298ºF).

1. Ignition OFF, remove the jumper wire, disconnect the harness connector at the K20 Engine Control Module, ignition ON.
2. Test for less than 1 V between the signal circuit and ground.
   • If 1 V or greater, repair the short to voltage on the circuit.
   • Go to next step: If less than 1 V
3. Ignition OFF.
4. Test for less than 2 Ω in the signal circuit end to end.
   • If 2 Ω or greater, repair the open/high resistance in the circuit.
   • If less than 2 Ω, replace the K20 Engine Control Module.

• Go to next step: If warmer than 148ºC (298ºF).

7. Test or replace the B75C Multifunction Intake Air sensor.

Component Testing

Multifunction Intake Air Sensor

1. Ignition OFF, disconnect the harness connector at the B75C Multifunction Intake Air Sensor.

NOTE: A thermometer can be used to test the sensor off the vehicle.

2. Test the IAT sensor 1 by varying the sensor temperature while monitoring the sensor resistance.

Compare the readings with the Temperature Versus Resistance - Intake Air Temperature Sensor table for Hitachi Sensors. The resistance values should be in range of the table values.

• If not within the specified range

Replace the B75C Multifunction Intake Air Sensor.

• Go to next step: If within the specified range

3. All OK.

Repair Instructions

• Perform the Diagnostic Repair Verification after completing the repair.
• Mass Airflow Sensor with Intake Air Temperature Sensor Replacement for multifunction intake air sensor replacement
• Control Module References for engine control module replacement, programming, and setup.

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