Diagnostic Instructions

DTC Descriptors

DTC P1111:  Intake Air Temperature (IAT) Sensor Circuit Intermittent High Voltage

DTC P1112:  Intake Air Temperature (IAT) Sensor Circuit Intermittent Low Voltage

Diagnostic Fault Information

Circuit	Short to Ground	Open/High Resistance	Short to Voltage	Signal Performance
IAT Sensor Signal	P0112, P1112	P0113, P1111	P0113, P1111¹	P0110, P0111
Low Reference	--	P0113, P1111	P0113, P1111¹	P0110, P0111
¹ 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: Varies with ambient temperature.
IAT Sensor Signal	130°C (266°F),	20°C (68°F)	20°C (68°F)¹
Low Reference	--	20°C (68°F)	--
¹ Internal ECM or sensor damage may occur if the circuit is shorted to B+.

Circuit Description

The intake air temperature (IAT) sensor is a variable resistor that measures the temperature of the air entering the engine. The IAT sensor has a signal circuit and a low reference circuit. The engine control module (ECM) supplies 5 volts to the IAT signal circuit and a ground for the IAT 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 DTC

P1111

P1112

Conditions for Setting the DTC

P1111

The ECM detects that the IAT sensor parameter is less than -38°C (-36°F) for more than 3 seconds intermittently.

P1112

The ECM detects that the IAT sensor is more than 149°C (300°F) for more than 20 seconds intermittently.

Action Taken When the DTC Sets

DTCs P1111 and P1112 are Type C DTCs.

Conditions for Clearing the MIL/DTC

DTCs P1111 and P1112 are Type C DTCs.

Reference Information

Schematic Reference

Engine Controls Schematics

Connector End View Reference

Electrical Information Reference

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Circuit/System Verification

1. Verify that DTCs P0112 or P0113 are not set.

⇒	If any of the DTCs are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle .

2. 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. DTC P1111 or P1112 should not set.

Circuit/System Testing

1. Start the engine, observe the intake air temperature (IAT) sensor parameter while moving the harness connector of the sensor. The IAT sensor parameter should not change abruptly.

⇒	If the IAT sensor parameter changes abruptly, repair the harness connector of the IAT sensor.

2. Engine running, observe the IAT sensor parameter while moving the harness connector of the engine control module (ECM). The IAT sensor parameter should not change abruptly.

⇒	If the IAT sensor parameter changes abruptly, repair the harness connector of the ECM.

3. Engine running, observe the IAT sensor parameter while moving the wiring harness between the sensor and ECM. The IAT sensor parameter should not change abruptly.

⇒	If the IAT sensor parameter changes abruptly, repair the wiring harness.

Component Testing

1. Ignition OFF, disconnect the harness connector of the intake air temperature (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 table and verify that the resistance is within 5 percent of the specification.

⇒	If the resistance vs. temperature is not within 5 percent, replace the IAT sensor.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.