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

Open/High Resistance

Short to Voltage

IAT Sensor Signal

P0112

P0113

P0113

Low Reference

--

P0113

P0113

Typical Scan Tool Data

IAT Sensor

Circuit

Short to Ground

Open or High Resistance

Short to Voltage

Operating Conditions: Engine running

Normal IAT Parameter: -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)

-40°C (-40°F)

Circuit/System Description

The intake air temperature (IAT) sensor is a variable resistor that 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 to the low reference circuit.

Conditions for Running the DTC

P0112

    • DTC P0116, P0117, P0118, P0125, P0128, P0608, or P0609 are not set.
    • The ECT sensor is less than 150°C (302°F).
    • The engine run time is greater than 10 seconds.
    •  This DTC runs continuously within the above enable conditions.

P0113

    • DTC P0101, P0102, P0103, P0116, P0117, P0118, P0125, 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 greater than 10 seconds.
    •  This DTC runs continuously within the above enable conditions.

Conditions for Setting the DTC

P0112

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

P0113

The IAT sensor is less than -39°C (-38°F) for greater 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 at the initial 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.
    • Depending on the ambient temperature, an IAT sensor signal circuit or low reference circuit that is shorted to the MAF sensor signal circuit can cause DTC P0113 to set. This condition causes a rapid fluctuation in the IAT Sensor parameter.
    • An IAT sensor signal circuit that is shorted to the MAF sensor ignition circuit can cause DTC P0113 to set.

Reference Information

Schematic Reference

Engine Controls Schematics

Connector End View Reference

Component 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

Control Module References for scan tool information

Circuit/System Verification

Important: 

   • Perform this 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.

  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. Ignition ON, observe the scan tool IAT and ECT Sensor parameters. The readings should be within 15°C (27°F) of each other and the ambient temperature.
  3. Ignition ON, observe the scan tool Start-up ECT and Start-up IAT Sensor parameters. Compare those sensor parameters to each other and also to the ambient temperature to determine if the IAT sensor is within an acceptable operating range.
  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

Important: All electrical components and accessories must be turned OFF and allowed to power down.

  1. Ignition OFF, disconnect the harness connector at the MAF/IAT sensor.
  2. Ignition OFF for 90 seconds, test for less than 5 ohms of resistance between the low reference circuit terminal E and ground.
  3. If greater than the specified range, 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 range, test the signal circuit terminal D for a short to ground. If the circuit tests normal, replace the ECM.
  6. Install a 3A fused jumper wire between the signal circuit terminal D and a good ground. Verify the scan tool IAT Sensor parameter is greater than 149°C (300°F).
  7. If less than the specified range, 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 or replace the IAT sensor.

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 .

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