Diagnostic Instructions

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	Signal Performance
IAT Sensor Signal	P0112	P0113	P0113*	--
Low Reference	--	P0113	P0113**	--
* Sensor damage may occur if the circuit is shorted to B+. ** Internal ECM 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	129°C (264°F), 0.0 Volts	-40°C (-40°F), 5.0 Volts	-40°C (-40°F), 5.0 Volts
Low Reference	--	-40°C (-40°F), 5.0 Volts	-40°C (-40°F), 5.0 Volts*
* Internal ECM damage may occur if the circuit is shorted to B+.

Circuit/System 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

Conditions for Setting the DTC

P0112

The ECM detects that the IAT sensor voltage is less than 0.01 volt for more than 3 seconds.

P0113

The ECM detects that the IAT sensor voltage is greater than 4.99 volts for more than 3 seconds.

Action Taken When the DTC Sets

DTC P0112 and P0113 are Type B DTCs.

Conditions for Clearing the MIL/DTC

DTC P0112 and P0113 are Type B DTCs.

Diagnostic Aids

Reference Information

Schematic Reference

Engine Controls Schematics

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 running for 1 minute, observe the DTC information with a scan tool. DTCs P0112 and 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 you observed from the Freeze Frame/Failure Records data.

Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the IAT sensor.
2. Ignition OFF, test for less than 5 ohms of resistance between the low reference circuit terminal 2 and ground.

⇒	If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the ECM.

3. Ignition ON, verify the scan tool IAT sensor parameter is at -40°C (-40°F).

⇒	If greater than the specified value, test the signal circuit for a short to ground. If the circuit tests normal, replace the ECM.

4. Install a 3A fused jumper wire between the signal circuit terminal 1 and the low reference circuit terminal 2. Verify the scan tool IAT sensor parameter is greater than 129°C (264°F).

⇒	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.

5. If all circuits test normal, test or replace the IAT sensor.

Component Testing

1. Ignition OFF, disconnect the harness connector at the 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 not within the specified range, replace the IAT sensor.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.