Diagnostic Instructions

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

P0111 Cruise Test

P0112 and P0113

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

Reference Information

Schematic Reference

Engine Controls Schematics

Connector End View Reference

Component Connector End Views

Electrical Information Reference

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).

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.

3. Test for less than 5 ohms between the low reference circuit terminal 3 and ground.

⇒	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.

4. Install the fuse that supplies B+ to circuit terminal X2-36 of the ECM.
5. Ignition ON, verify the scan tool IAT sensor parameter is at -40°C (-40°F).

⇒	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.

6. 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).

⇒	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.

7. 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.

Important: A thermometer can be used to test the sensor off the vehicle.

2. 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.

⇒	If not within the specified range, replace the IAT sensor.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.