For 1990-2009 cars
Engine Controls Components
Cell 20:Engine Data Sensors
OBD II Symbol Description 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 air temperature is cold, and the IAT sensor's resistance is low when the 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

Temperature input is -40°C (-40°F) for at least 0.5 seconds.

or

Temperature input is 140°C (284°F) 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 in which the intake air temperature will default to 20°C (68°F).

### 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.

### Diagnostic Aids

Check for a faulty electrical connection to the PCM.

Use the Temperature vs Resistance table in order to evaluate the possibility of a shifted (incorrectly calibrated) IAT sensor. A shifted sensor could result in a DTC P0110. Refer to Temperature Versus Resistance .

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 connectors 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.

Repair any electrical circuit faults that were found. Refer to Wiring Repairs .

If a DTC P0110 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 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 for a high input condition. If the scan tool reads 140°C (284°F) the input circuit may be the result of an short circuit.

3. This step checks for a low input condition. If the scan tool reads -40°C (-40°F) the input circuit may be the result of an open circuit.

4. This step determines if DTC P0110 is the result of a hard failure or an intermittent condition

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 | Select the IAT sensor parameter on the scan tool. Is the IAT sensor value greater than or at the specified value? | 140°C (284°F) | Go to Step 5 | Go to Step 3
3 | Select the IAT sensor parameter on the scan tool. Is the IAT sensor value less than or at the specified value? | -40°C (-40°F) | Go to Step 7 | Go to Step 4
4 |

1. Perform the scan tool Clear DTC Information function.
2. Place the vehicle into Check Mode, using the scan tool.
3. Operate the vehicle within the Freeze Frame conditions as specified.

Does the DTC P0110 set?

--

Go to Step 2

Go to Diagnostic Aids

5 |

1. Turn ON the ignition, leaving the engine OFF.
2. Disconnect the IAT sensor electrical connector.
3. Select the IAT sensor parameter on the scan tool.

Is the IAT sensor value at the specified value?

-40°C (-40°F)

Go to Step 13

Go to Step 6

6 |

1. Turn the ignition switch OFF.
2. Disconnect the PCM electrical connector at the PCM.
3. Check the IAT sensor input circuit for a short to ground.

Ensure the input circuit is not shorted to the sensor ground circuit.

4. Repair as necessary. Refer to Wiring Repairs in Wring System.

Is the action complete?

--

Go to Step 15

Go to Step 14

7 |

1. Disconnect the IAT sensor electrical connector.
2. Jump the IAT input circuit and the sensor ground circuit together at the IAT sensor harness connector.
3. Select the IAT sensor parameter on the scan tool.

Is the IAT sensor value greater than or at the specified value?

140°C (284°F)

Go to Step 9

Go to Step 8

8 |

1. Jump the IAT input circuit at the IAT sensor harness connector to chassis ground.
2. Select the IAT sensor parameter on the scan tool.

Is the IAT sensor value greater than or at the specified value?

140°C (284°F)

Go to Step 10

Go to Step 11

9 |

1. Check for faulty electrical connections at the IAT sensor.
2. Repair as necessary.

Was a repair necessary?

--

Go to Step 15

Go to Step 13

10 |

1. Turn OFF the ignition.
2. Disconnect the PCM connector at the PCM.
3. Check the IAT sensor ground circuit for an open.
4. Repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Was a repair necessary?

--

Go to Step 15

Go to Step 12

11 |

1. Turn OFF the ignition.
2. Disconnect the PCM connector at the PCM.
3. Check the IAT sensor input circuit for an open or short.
4. Repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Was a repair necessary?

--

Go to Step 15

Go to Step 12

12 |

1. Check for a faulty IAT circuit terminal connection at the PCM.
2. Replace the terminals as necessary.

Was a problem found?

--

Go to Step 15

Go to Step 14

13 | Replace the IAT sensor. Refer to Intake Air Temperature Sensor Replacement . Is the action complete? | -- | Go to Step 15 | --
14 | Replace the PCM. Refer to Powertrain Control Module Replacement . Is the action complete? | -- | Go to Step 15 | --
15 |

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 scan tool?

--

Go to the applicable table

System OK