For 1990-2009 cars
Engine Controls Components
Cell 20: Engine Data Sensors
OBD II Symbol Description Notice
Handling ESD Sensitive Parts Notice
Handling ESD Sensitive Parts Notice

### Circuit Description

The intake air temperature (IAT) sensor is a thermistor. A thermistor is a resistor whose value varies with temperature. The IAT sensor's resistance is high when the outside air temperature is cold, and the IAT sensor's resistance is low when the outside air temperature is warm. The IAT sensor is wired in series with a fixed resistor in the powertrain control module (PCM). The PCM applies 5 volts to the IAT sensor. The PCM monitors the voltage across the IAT sensor and converts the voltage into a temperature reading. The PCM will receive a high voltage input when the air temperature is cold. The PCM will receive a low voltage input when the air temperature is warm.

### Conditions for Running the DTC

The ignition is ON.

### Conditions for Setting the DTC

• | The IAT sensor signal voltage indicates that the intake air temperature is less than -40°C (-40°F).

• | The above condition is present for at least 0.5 seconds.

### Action Taken When the DTC Sets

• | The PCM illuminates the malfunction indicator lamp (MIL).

• | The PCM records the operating conditions at the time the diagnostic fails. This information is stored in the Freeze Frame buffer.

• | The PCM enters the Fail-Safe Function and assumes the intake air temperature is 20°C (68°F) while stopping EGR control.

### Conditions for Clearing the MIL/DTC

• | The MIL turns OFF after three consecutively passing trips without a fault present.

• | A History DTC clears after 40 consecutive warm-up cycles without a fault.

• | Use the scan tool Clear DTC Information function or disconnect the PCM battery feed in order to clear the DTC.

### Diagnostic Aids

Check for any of the following conditions:

• | A faulty electrical connection to the PCM.

• | Use the Temperature vs Resistance table in order to check the IAT sensor at various temperature levels and evaluate the possibility of a shifted (incorrectly calibrated) sensor. A shifted sensor could result in a driveability complaint. Refer to Temperature Versus Resistance .

• | When a DTC P0108, P0113, P0118, and P0123 are set together the cause could be an open ground circuit.

• | A shorted to voltage IAT sensor signal circuit may cause a DTC P0113 to set.

An intermittent malfunction may be caused by a fault in the IAT sensor electrical circuit. Inspect the wiring harness and components for any of the following conditions:

• | Backed out terminals.

• | Improper mating of terminals.

• | Broken electrical connector locks.

• | Improperly formed or damaged terminals.

• | Faulty terminal to wire connections.

• | Physical damage to the wiring harness.

• | A broken wire inside the insulation.

• | Corrosion of electrical connections, splices, or terminals.

If a DTC P0113 cannot be duplicated, the information included in the Freeze Frame data can be useful in determining vehicle operating conditions when the DTC was first set.

### Test Description

The numbers below refer to the step numbers in the Diagnostic Table.

1. The Powertrain OBD System Check prompts the technician to complete some basic checks and store the freeze frame data on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.

2. This step checks the current IAT sensor reading.

3. This step determines if the fault is present.

4. This step determines if there is a fault in the IAT circuit wiring.

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | Go to Step 2 | Go to Powertrain On Board Diagnostic (OBD) System Check
2 |

1. Turn ON the ignition, leaving the engine OFF.
2. Install a scan tool.
3. Observe the IAT parameter on the scan tool data list.

Is the IAT display at or less than the specified value?

-40°C (-40°F)

Go to Step 4

Go to Step 3

3 |

1. Turn ON the ignition, leaving the engine OFF.
2. Clear the scan tool information.
3. Operate the vehicle within the Freeze Frame conditions as noted.

Is a DTC P0113 set?

--

Go to Step 4

Go to Diagnostic Aids

4 |

1. Disconnect the IAT sensor electrical connector.
2. Jumper the IAT sensor signal (input) circuit and the sensor ground circuit together at the IAT sensor harness connector.
3. Observe the IAT parameter on the scan tool.

Is the IAT display at the specified value?

119°C (246°F)

Go to Step 6

Go to Step 5

5 |

1. Jumper the IAT sensor signal (input) circuit at the sensor harness connector to chassis ground.
2. Observe the IAT parameter on the scan tool.

Is the IAT display at the specified value?

119°C (246°F)

Go to Step 7

Go to Step 8

6 |

1. Check for a faulty connection at the IAT sensor.
2. Repair as necessary.

Was a repair necessary?

--

Go to Step 12

Go to Step 10

7 |

1. Turn OFF the ignition.
2. Disconnect the PCM.
3. Check the IAT sensor ground circuit for an open circuit.

Was a repair necessary?

--

Go to Step 12

Go to Step 9

8 |

1. Turn OFF the ignition.
2. Disconnect the PCM.
3. Check the IAT sensor signal (input) circuit for an open.
4. Repair as necessary.

Was a repair necessary?

--

Go to Step 12

Go to Step 9

9 |

1. Check for a faulty sensor ground at the IAT sensor signal (input) circuit terminal connection at the PCM.
2. Repair as necessary.

Was a repair necessary?

--

Go to Step 12

Go to Step 11

10 | Replace the IAT sensor. Refer to Intake Air Temperature Sensor Replacement . Is the action complete? | -- | Go to Step 12 | --
11 | Replace the PCM. Refer to Powertrain Control Module Replacement . Is the action complete? | -- | Go to Step 12 | --
12 |

1. Clear the scan tool information and road test the vehicle within the Freeze Frame conditions that set the DTC.
2. Review the scan tool data and check for DTCs. The repair is complete if no DTCs are stored.

Are any DTCs displayed on the scan tool?

--

Go to the Applicable DTC Table

System OK