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 provides 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

Signal Performance

IAT Sensor Signal

P0112

P0113

P0113

P0113

P0111

Low Reference

--

--

P0113

--

--

Typical Scan Tool Data

IAT Sensor

Circuit

Short to Ground

Open or High Resistance

Short to Voltage

Operating Conditions: The ignition is ON or the engine is running

Normal IAT Parameter: -39°C to +120°C (-38°F 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 is a variable resistor. The IAT sensor has a signal circuit and a low reference circuit. The IAT sensor 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 P0116, P0117, P0118, P0128, P0608, or P0609 are not set.
    • The ECT sensor is less than 150°C (302°F).
    • The engine run time is more than 10 seconds.
    •  DTC  P0112 runs continuously within the above enable conditions.

P0113

    • DTC P0101, P0102, P0103, P0116, P0117, P0118, P0128, P0608, or P0609 are not set.
    • The ECT sensor is greater than -40°C (-40°F).
    • The mass air flow (MAF) sensor is less than 512 g/s.
    • The engine run time is more than 10 seconds.
    •  DTC  P0113 runs continuously within the above enable conditions.

Conditions for Setting the DTC

P0112

The IAT sensor is more than 148°C (298°F)  for more than 5 seconds.

P0113

The IAT sensor is less than -39°C (-38°F)  for more than 5 seconds.

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, then at ignition ON a properly functioning IAT sensor will gradually increase the scan tool IAT Sensor parameter. This is due to the heat that is generated by the MAF sensor heating elements.

Reference Information

Schematic Reference

Engine Controls Schematics

Connector End View Reference

    •  Engine Controls Connector End 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
    •  Scan Tool Output Controls

Circuit/System Verification

  1. Engine running, observe the scan tool IAT Sensor parameter. The reading should be between -39 to +120°C (-38 to +248°F) depending on the current ambient temperature and the vehicle operating conditions.
  2. Important: 

       • Perform this verification procedure only when the ignition has been OFF for 8 hours or more.
       • The IAT will begin to warm up as soon as the ignition key is turned ON

  3. Ignition ON, observe the scan tool IAT Sensor and ECT Sensor parameters. The readings should be within 15°C (27°F) of each other and also the ambient temperature.
  4. Engine running, observe the DTC information with a scan tool. DTCs P0112 or P0113 should not set.
  5. 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.

Circuit/System Testing

  1. Ignition OFF, disconnect the harness connector at the MAF/IAT sensor.
  2. Ignition OFF, allow sufficient time for the control module to power down. Test for less than 5 ohms of resistance between the low reference circuit terminal D 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 parameter is less than -39°C (-38°F).
  5. If greater than the specified value, test the signal circuit terminal E 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 E and a ground. Verify the scan tool IAT Sensor 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. Refer to Component Testing.

Component Testing

Measure the resistance of the IAT sensor and compare the IAT sensor resistance to the values listed in the Temperature vs. Resistance table. Refer to Temperature Versus Resistance .

If the resistance is not within 9 percent of the range listed in the Temperature vs. Resistance table, replace the IAT sensor.

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