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
DTC P0114: Intake Air Temperature (IAT) Sensor Circuit Intermittent

### Diagnostic Fault Information

Circuit | Short to Ground | High Resistance | Open | Short to Voltage | Signal Performance
--- | --- | --- | --- | --- | ---
IAT Sensor Signal | P0112, P0114 | P0113, P0114 | P0113, P0114 | P0113, P0114 | P0114, P2199
Low Reference | -- | P0113, P0114 | P0113, P0114 | P0113, P0114 | P0114, P2199

### Typical Scan Tool Data

#### IAT Sensor

Circuit | Short to Ground | Open | Short to Voltage
--- | --- | --- | ---
Operating Conditions: Engine Running Parameter Normal Range: Varies with ambient temperature
IAT Sensor Signal | 143°C (289°F) | -40°C (-40°F) | -40°C (-40°F)
Low Reference | -- | -40°C (-40°F) | -40°C (-40°F)

### Circuit/System Description

The intake air temperature (IAT) sensor is integrated with the mass air flow (MAF) sensor. The IAT sensor is a variable resistor that measures the temperature of the air when it first enters the induction system. The engine control module (ECM) supplies 5V to the IAT signal circuit and a ground for the IAT low reference circuit.

### Conditions for Running the DTC

#### P0112

• | The ignition is ON or the engine is running.

• | This DTC runs continuously within the enabling conditions.

#### P0113

• | The engine is running.

• | This DTC runs continuously within the enabling conditions.

#### P0114

• | The ignition is ON or the engine is running.

• | This DTC runs continuously within the enabling conditions.

### Conditions for Setting the DTC

#### P0112

The ECM detects that the IAT is warmer than 142°C (288°F) for greater than 15 seconds.

#### P0113

The ECM detects that the IAT is colder than -39°C (-38°F) for greater than 15 seconds at idle.

#### P0114

The ECM detects that the IAT sensor signal is intermittent or has abruptly changed for greater than 4 seconds.

### Action Taken When the DTC Sets

DTCs P0112, P0113, P0114 are Type B DTCs.

### Conditions for Clearing the MIL/DTC

DTCs P0112, P0113, P0114 are Type B DTCs.

### Diagnostic Aids

• | When the engine is cold, at ignition ON, a properly functioning IAT sensor will gradually increase the scan tool IAT Sensor parameter. This is due to the heat that is generated by the MAF sensor heating elements.

• | Depending on the ambient temperature, an IAT sensor signal circuit that is shorted to the MAF sensor signal circuit can cause a DTC P0113 and/or a DTC P0114 to set. This condition may cause either a rapid fluctuation in the IAT Sensor parameter or cause it to become stuck at a given value.

• | An IAT low reference circuit that is open can cause the IAT Sensor parameter response to be sluggish.

• | A MAF sensor ground circuit that is open will cause a DTC P0113 and/or a DTC P0114 to set.

### 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

• | If the ignition has been OFF for 8 hours or greater, the IAT, the IAT 2 and the engine coolant temperature (ECT) should be within 9°C (16°F) of each other. Ignition ON, observe the scan tool IAT Sensor, IAT Sensor 2 and the ECT Sensor parameters. Compare those sensor parameters to each other to determine if the condition is current.

• | Engine running, observe the scan tool IAT Sensor parameter. The reading should be between -39 to +120°C (-38 to +248°F) depending on the current ambient temperature and the vehicle operating conditions.

• | 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 B75B MAF/IAT sensor.
2. Ignition OFF, test for less than 5Ω between the MAF sensor ground circuit terminal B and ground.

⇒ | If greater than the specified range, test the MAF sensor ground circuit for an open/high resistance.

3. Ignition OFF, test for less than 5Ω between the IAT low reference circuit terminal D 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 K20 ECM.

4. Ignition ON, verify the scan tool IAT Sensor parameter is colder than -39°C (-38°F).

⇒ | If warmer than the specified range, test the signal circuit terminal E for a short to ground. If the circuit tests normal, replace the K20 ECM.

5. Install a 3A fused jumper wire between the signal circuit terminal E and ground. Verify the scan tool IAT Sensor parameter is warmer than 142°C (288°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 K20 ECM.

6. If the circuits test normal, test or replace the MAF sensor.

### Component Testing

Measure and record the resistance of the IAT sensor at various ambient temperatures, then compare those measurements to the Temperature Versus Resistance table.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Mass Airflow Sensor Replacement

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