For 1990-2009 cars

### 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 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 | P0114
Low Reference | -- | P0113 | P0113 | P0114

### 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 | 150°C (302°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 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

#### P0112

• | DTCs P0116, P0117, P0118, or P0502 are not set.

• | The engine run time is greater than 10 seconds.

• | The engine coolant temperature (ECT) is less than 150°C (302°F).

• | The vehicle speed is greater than 0 km/h (0 mph).

• | The DTC runs continuously once the above conditions are met.

#### P0113

• | DTCs P0106, P0107, P0108, P0116, P0117, P0118, or P0502 are not set.

• | The engine run time is greater than 10 seconds.

• | The airflow into the engine is less than 512 g/s.

• | The ECT sensor is greater than -40°C (-40°F).

• | The vehicle speed is less than 512 km/h (318 mph).

• | The DTC runs continuously once the above conditions are met.

### Conditions for Setting the DTC

#### P0112

The ECM detects that the IAT sensor is greater than 149°C (300°F) for greater than 6 seconds.

Note: The scan tool only displays to -40°C (-40°F).

#### P0113

The ECM detects that the IAT sensor parameter is colder than -60°C (-76°F) for greater than 6 seconds.

### Action Taken When the DTC Sets

• | DTC P0112 and P0113 are Type B DTCs.

• | The ECM commands the cooling fans ON.

### Conditions for Clearing the MIL/DTC

DTC P0112 and P0113 are Type B DTCs.

### 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, observe the DTC information with a scan tool. 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 you observed from the Freeze Frame/Failure Records data.

### Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the MAF/IAT sensor.
2. Ignition OFF for 1 minute, test for less than 5 Ω between the low reference circuit terminal 1 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 warmer than the specified range, test the signal circuit terminal 3 for a short to ground. If the circuit tests normal, replace the ECM.

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

4. Install a 1 A fused jumper wire between the signal circuit terminal 3 and ground. Verify the scan tool IAT sensor parameter is greater than 149°C (300°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 MAF/IAT sensor.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Mass Airflow Sensor with Intake Air Temperature Sensor Replacement

• | Control Module References for ECM replacement, setup, and programming.