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 Descriptor

DTC P0111: Intake Air Temperature (IAT) Sensor Performance

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

IAT Sensor Signal

P0110, P0112

P0110, P0113

P0110, P0113

P0111, P011B

Low Reference

--

P0110, P0113, P0115, P0118, P0120, P0123, P0220, P0223, P0450, P0453

--

P0111, P011B

Typical Scan Tool Data

IAT Sensor

Circuit

Short to Ground

Open

Short to Voltage

Operating Conditions: Engine operating in Closed Loop.

Parameter Normal Range: -40 to +140°C (-40 to +284°F) Varies with coolant temperature.

IAT Sensor Signal

140°C (284°F)

-40°C (-40°F)

-40°C (-40°F)

Low Reference

--

-40°C (-40°F)

-40°C (-40°F)

Circuit Description

The intake air temperature (IAT) sensor is a variable resistor that measures the temperature of the engine coolant. The powertrain control module (PCM) supplies 5 volts to the IAT signal circuit and supplies a ground to the low reference circuit. The PCM monitors the mutual performance of the IAT and the engine coolant temperature (ECT) signals. The PCM monitors the warm up and cool down behavior of the sensors, after a vehicle driven at operating temperature is shut down. If the PCM detects that the IAT is not with in a predetermined range of ECT after a long soak, or the IAT and ECT are not within a range of each other, as compared to a previous cold start, this DTC sets.

The following table illustrates the difference between temperature, resistance, and voltage:

Temperature

ECT Resistance

ECT Signal Voltage

Cold

High

High

Warm

Low

Low

Conditions for Running the DTC

    • The engine coolant temperature is at a specified value at engine start up.
    • The engine has been running for greater than 250 seconds.
    • Vehicle speed has exceeded 65 km/h (40 mph).
    • DTC P0111 runs continuously once the above conditions are met.

Conditions for Setting the DTC

The IAT sensor input changes less than a specified value during engine warm up.

Action Taken When the DTC Sets

DTC P0111 is a Type B DTC.

Conditions for Clearing the MIL/DTC

DTC P0111 is a Type B DTC.

Diagnostic Aids

    • Test the IAT sensor at various temperature levels in order to evaluate the possibility of a skewed sensor. A skewed sensor can result in a DTC or a driveability condition. Refer to Temperature Versus Resistance.
    • If the vehicle has sat overnight, the IAT sensor and the ECT sensor values should display within 3°C (5°F).
    • High resistance in the circuit of the ECT sensor could set a DTC.

Reference Information

Schematic Reference

Engine Controls Schematics

Connector End View Reference

    •  Powertrain Control Module Connector End Views
    •  Engine Controls 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

  1. Verify that the following DTCs are not set: P0110, P0112 and P0113.
  2. If any of the DTCs are set, refer to DTC P0110, P0112, or P0113.
  3. Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. 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 MAF/IAT sensor.
  2. Test for less than 10 ohms between the low reference circuit terminal 5 and ground G104.
  3. If greater than the specified range, test the low reference circuit for an open/high resistance, or for a short to voltage. If the circuit tests normal, replace the PCM.
  4. Ignition ON, verify the scan tool IAT sensor parameter is at -40°C (-40°F).
  5. If greater than the specified value, test the signal circuit for a short to ground. If the circuit tests normal, replace the PCM.
  6. Install a 3A fused jumper wire between the signal circuit terminal 4 and the low reference circuit terminal 5. Verify the IAT sensor parameter is greater than 139°C (280°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 PCM.
  8. If all circuits test normal, test or replace the IAT sensor.

Component Testing

  1. Ignition OFF, disconnect the harness connector at the intake air temperature (IAT) sensor.
  2. Important: A thermometer can be used to test the sensor off the vehicle.

  3. Test the IAT sensor by varying the sensor temperature while monitoring the sensor resistance. Compare the readings with the Temperature Versus Resistance table and verify that the resistance is within 5 percent of the specification.
  4. If not within the specified range, replace the IAT sensor.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Intake Air Temperature Sensor Replacement
    •  Control Module References for control module replacement, setup, and programming