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 P0111: Intake Air Temperature (IAT) Sensor Circuit Performance

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

Signal Performance

IAT Sensor Signal

P0112

P0111, P0113

P0113*

P0111

Low Reference

--

P0111, P0113

P0113*

P0111

* Internal ECM or sensor damage may occur if the circuit is shorted to B+

Typical Scan Tool Data

IAT Sensor

Circuit

Short to Ground

Open

Short to Voltage

Operating Conditions: Engine operating in Closed Loop.

Parameter Normal Range: -39° to +134°C (-38° to +274°F) Varies with ambient temperature.

IAT Sensor Signal

135°C (275°F)

-40°C (-40°F)

-40°C (-40°F)*

Low Reference

--

-40°C (-40°F)

-40°C (-40°F)*

* Internal ECM or sensor damage may occur if the circuit is shorted to B+

Circuit Description

The intake air temperature (IAT) sensor is an integral part of the mass air flow (MAF) sensor. The IAT sensor is a variable resistor that measures the temperature of the intake air. The engine control module (ECM) supplies 5 volts to the IAT signal circuit and supplies a ground to the low reference circuit.

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

IAT

IAT Resistance

IAT Signal Voltage

Cold

High

High

Warm

Low

Low

Conditions for Running the DTCs

P0111 Idle Test

    • Before the ECM can report DTC P0111 failed, DTC P0101 must run and pass.
    • DTC P0112, P0113, P0116, P0117, P0118, P0119, or P0128 is not set.
    • The engine coolant temperature (ECT) at engine start is less than 60°C (140°F).
    • The ECT is greater than 65°C (149°F).
    •  The vehicle speed is less than 11 km/h (7 mph).
    • The idle test consists of 5 idle periods when the vehicle speed was previously greater than 11 km/h (7 mph).
    •  DTC P0111 runs continuously once the above conditions are met for greater than 2 seconds in each sample period.

P0111 Cruise Test

    • Before the ECM can report DTC P0111 failed, DTC P0101 must run and pass.
    •  DTC P0112, P0113, P0116, P0117, P0118, P0119, or P0128 is not set.
    • The ECT at engine start is less than 60°C (140°F).
    • The vehicle speed is greater than 39 km/h (24 mph).
    • The MAF is between 11-42 g/s.
    • Decel fuel cut-off (DFCO) is not active.
    • The cruise test consists of 16 cruise periods when the vehicle speed was previously less than 39 km/h (24 mph).
    • DTC P0111 runs continuously once the above conditions are met for greater than 2 seconds in each sample period.

P0112 and P0113

    • The engine run time is greater than 18 seconds.
    • The engine is idling for greater than 10 seconds.
    • The DTCs runs continuously once the above conditions are met.

Conditions for Setting the DTC

P0111

The ECM detects that the IAT remains steady within 2°C (4°F) during the idle test. Or, the ECM detects that the IAT decreased less than 2°C (4°F) during the cruise test. The condition exists for greater than 4 seconds or for a cumulative of 50 seconds.

P0112

The ECM detects that the intake air temperature is greater than 132°C (270°F) for greater than 4 seconds or cumulative of 50 seconds.

P0113

The ECM detects that the intake air temperature is less than -42°C (-44°F) and remains steady within 3°C (5°F) during an air flow increase of greater than 999 grams. The scan tool is limited to -40°C (-40°F), so the diagnostic procedure uses -39°C (-38°F) to determine if there is an IAT condition. The condition exists for greater than 4 seconds or cumulative of 50 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

The following table illustrates the ECM connector locations:

ECM Connector Location

X2

X1

Front of Vehicle

    • If the vehicle has sat overnight, the IAT sensor and the ECT sensor values should display within 3°C (5°F).
    • High resistance on either the IAT sensor signal circuit or the IAT sensor low reference circuit could set a DTC.

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

  1. Engine idling for 1 minute, observe the scan tool DTC information. DTCs P0112, or P0113 should not set.
  2. 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 are captured in the Freeze Frame/Failure Records Data List.

Circuit/System Testing

  1. Ignition OFF, disconnect the harness connector at the MAF/IAT sensor.
  2. Remove the fuse that supplies B+ to circuit terminal X2-36 of the engine control module (ECM).
  3. Notice: Do NOT use a test lamp to test the continuity of the circuit. Damage to the control module may occur due to excessive current draw.

  4. Test for less than 5 ohms between the low reference circuit terminal 3 and ground.
  5. 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/connections test normal, replace the ECM.
  6. Install the fuse that supplies B+ to circuit terminal X2-36 of the ECM.
  7. Ignition ON, verify the scan tool IAT sensor parameter is at -40°C (-40°F).
  8. If greater than the specified range, test the signal circuit for a short to ground. If the circuit/connections test normal, replace the ECM.

    Important: If the fuse in the jumper wire opens, the signal circuit is shorted to a voltage and the sensor may be damaged.

  9. Ignition ON, install a 3A fused jumper wire between the signal circuit terminal 1 and low reference circuit terminal 3. Verify the IAT sensor parameter is greater than 134°C (274°F).
  10. If less than the specified range, test the signal circuit for a short to voltage or an open/high resistance. If the circuit/connections test normal, replace the ECM.
  11. If all circuits/connections test normal, test or replace the MAF/IAT sensor.

Component Testing

  1. Ignition OFF, disconnect the harness connector of the MAF/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 - Intake Air Temperature Sensor 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.

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