For 1990-2009 cars

### Circuit Description

The DTC P0110 Intake Air Temperature (IAT) Sensor Circuit diagnostic detects an out of range sensor signal. The IAT sensor is a thermistor that is an integral part of the mass air flow (MAF) sensor. The electrical resistance of the IAT sensor is high when the air temperature is cold, and the resistance is low when the air temperature is warm. The IAT sensor is wired in series with a fixed resistor located 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 voltage measured by the PCM will be high when the air temperature is cold, and low when the air temperature is warm.

### Conditions for Running the DTC

The ignition is ON.

### Conditions for Setting the DTC

• | The temperature input is -40°C (-40°F) for at least 0.5 seconds.

| OR

• | The 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 3 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

Use the Temperature vs Resistance table in order to evaluate the possibility of a shifted 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 the components for an intermittent condition. Refer to Intermittent Conditions .

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 on the diagnostic table.

1. The Diagnostic System Check-Engine Controls 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 shorted to the sensor ground circuit.

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

4. This step checks whether the DTC P0110 is the result of a hard failure or an intermittent condition. Operating the vehicle in check mode enhances the PCM diagnostic capabilities. For additional information on check mode operation refer to the Powertrain Control Module Diagnosis section.

Step | Action | Values | Yes | No
--- | --- | --- | --- | ---
Schematic Reference: Engine Controls Schematics
1 | Did you perform the Diagnostic System Check-Engine Controls? | -- | Go to Step 2 | Go to Diagnostic System Check - Engine Controls
2 | Select the IAT sensor parameter on the scan tool. Is the IAT sensor value more than or equal to 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. Clear the DTC Information with the scan tool.
2. 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, with the engine OFF.
2. Disconnect the MAF sensor electrical connector.
3. Observe the MAF sensor parameter on the scan tool.

Is the IAT sensor value equal to the specified value?

-40°C (-40°F)

Go to Step 13

Go to Step 6

6 |

1. Turn OFF the ignition.
2. Inspect the IAT sensor input circuit for a short to ground. Ensure the input circuit is not shorted to the sensor ground circuit.
3. Repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Is the action complete?

--

Go to Step 15

Go to Step 14

7 |

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

Is the IAT sensor value more than or equal to the specified value?

140°C (284°F)

Go to Step 9

Go to Step 8

8 |

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

Is the IAT sensor value more than or equal to the specified value?

140°C (284°F)

Go to Step 10

Go to Step 11

9 |

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

Was a repair necessary?

--

Go to Step 15

Go to Step 13

10 |

1. Turn OFF the ignition.
2. Inspect the IAT sensor ground circuit for an open.
3. 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. Inspect the IAT sensor input circuit for an open or a short.
3. 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 faulty IAT circuit terminal connections at the PCM.
2. Repair as necessary. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

Was a repair necessary?

--

Go to Step 15

Go to Step 14

13 | Replace the MAF sensor. Refer to Mass Airflow 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. Use the scan tool in order to clear the DTCs.
2. Turn OFF the ignition for 30 seconds.
3. Start the engine.
4. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC run and pass?

--

Go to Step 16

Go to Step 2

16 | With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? | -- | Go to Diagnostic Trouble Code (DTC) List | System OK