GM Service Manual Online
For 1990-2009 cars only

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 provide an overview of each diagnostic category.

DTC Descriptors

DTC P0112: Intake Air Temperature (IAT) Sensor Circuit Low Voltage

DTC P0113: Intake Air Temperature (IAT) Sensor Circuit High Voltage

Diagnostic Fault Information

Circuit

Short to Ground

High Resistance

Open

Short to Voltage

IAT Sensor Signal

P0112

P0113

P0113

P0113

IAT Low Reference

--

P0113

P0113

--

Typical Scan Tool Data

IAT Sensor 1

Circuit

Short to Ground

Open or High Resistance

Short to Voltage

Operating Conditions: Engine Running

Normal Range: Varies between -39 to +120°C (-38 to +248°F)

IAT Sensor Signal

149°C (300°F)

-40°C (-40°F)

-40°C (-40°F)

IAT Low Reference

--

-40°C (-40°F)

--

Circuit/System Description

The intake air temperature (IAT) sensor 1 is a variable resistor. The IAT sensor 1 measures the temperature of the air entering the engine. The engine control module (ECM) supplies 5 volts to the IAT signal circuit, and a ground for the IAT low reference circuit. When the IAT sensor is cold, the sensor resistance is high. When the air temperature increases, the sensor resistance decreases. With high sensor resistance, the ECM detects a high voltage on the IAT signal circuit. With lower sensor resistance, the ECM detects a lower voltage on the IAT signal circuit.

Conditions for Running the DTC

P0112

    • DTC P0113 is not set.
    • Battery voltage is more than 7 V.
    • Key switch is ON.

P0113

    • DTC P0112 is not set.
    • Battery voltage is between 10-16 V.
    • Key switch is ON.
    • Engine is running for more than 10 seconds.

Conditions for Setting the DTC

P0112

IAT sensor voltage is less than 0.1 V.

P0113

IAT sensor voltage is more than 4.9 V.

Action Taken When the DTC Sets

DTCs P0112 and P0113 are Type B DTCs.

Conditions for Clearing the MIL/DTC

DTCs P0112 and P0113 are Type B DTCs.

Diagnostic Aids

    • If the engine is cold and the ignition is turned ON, a properly functioning IAT sensor 1 will gradually increment to a higher value. This is due to the heat that is generated by the MAF sensor heating elements.
    • Depending on the ambient temperature, an IAT sensor 1 signal circuit or low reference circuit that is shorted to the MAF sensor signal circuit can cause a DTC P0113 to set.
    • An IAT sensor 1 signal circuit that is shorted to the MAF sensor ignition circuit can cause a DTC P0113 to set.
    • Verify that any electrical aftermarket devices are properly connected and grounded. Refer to Checking Aftermarket Accessories .

Reference Information

Schematic Reference

Engine Controls Schematics

Connector End View Reference

    •  Engine Controls Component Views
    •  Engine Control Module Connector End Views

Electrical Information Reference

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

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

    •  Scan Tool Data List
    •  Scan Tool Data Definitions

Circuit/System Verification

Important: Perform this verification procedure only if the ignition has been OFF for 8 hours or more.

Ignition ON, observe the scan tool IAT Sensor 1, IAT Sensor 2, and ECT Sensor parameters. The readings should be within 8°C (15°F) of each other and also the ambient temperature.

Circuit/System Testing

  1. Ignition OFF, disconnect the harness connector at the mass air flow (MAF)/IAT sensor.
  2. Ignition OFF, test for less than 5 ohms of resistance between the low reference circuit terminal 1 and ground.
  3. If greater than the specified value, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the ECM.
  4. Ignition ON, verify the scan tool IAT Sensor 1 parameter is less than -39°C (-38°F).
  5. If greater than the specified value, test the signal circuit terminal 2 for a short to ground. If the circuit tests normal, replace the ECM.

    Important: If a short to voltage is found on the IAT signal circuit, the 3A fuse in the jumper wire will open.

  6. Install a 3A fused jumper wire between the signal circuit terminal 2 and a ground. Verify the scan tool IAT Sensor 1 parameter is greater than 149°C (300°F).
  7. If less than the specified value, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the ECM.
  8. If all circuits test normal, test the MAF/IAT sensor.

Component Testing

    • Ignition OFF, disconnect the harness connector at the MAF/IAT sensor.
    • Measure the resistance between the signal terminal 2 and the low reference circuit terminal 1 at the sensor. Compare the value to the Temperature Vs Resistance table. Verify the resistance is within 5 percent of the specification. Refer to Temperature Versus Resistance .

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Mass Airflow Sensor/Intake Air Temperature Sensor Replacement
    •  Control Module References for ECM replacement, setup, and programming