For 1990-2009 cars

### Circuit Description

The intake air temperature (IAT) sensor is a variable resistor. The IAT sensor has a signal circuit and a low reference circuit. The IAT sensor measures the temperature of the air entering the engine. The powertrain control module (PCM) supplies 5 volts to the IAT signal circuit and a ground for the IAT low reference circuit. When the IAT sensor is cold, the sensor resistance is high. When the air temperature increases, the sensor resistance decreases. With high sensor resistance, the PCM detects a high voltage on the IAT signal circuit. With lower sensor resistance, the PCM detects a lower voltage on the IAT signal circuit. If the PCM detects an intermittent high IAT signal voltage, indicating a low temperature, DTC P1111 sets .

### Conditions for Running the DTC

• | DTCs P0101, P0102, P0103, P0116, P0117, P0118, P0502 or P0503 are not set.

• | The vehicle speed sensor (VSS) is less than 56 km/h (35 mph).

• | The mass air flow (MAF) is less than 12 g/s.

• | The engine coolant temperature (ECT) is more than 60°C (140°F).

• | The engine run time is more than 180 seconds.

### Conditions for Setting the DTC

The intake air temperature (IAT) is less than -39°C (-38°F) for more than 3 seconds.

### Action Taken When the DTC Sets

• | The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.

• | The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

### Conditions for Clearing the MIL/DTC

• | The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.

• | A current DTC, Last Test Failed, clears when the diagnostic runs and passes.

• | A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.

• | Clear the MIL and the DTC with a scan tool.

Step | Action | 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 | Observe the DTC Information with a scan tool. Is DTC P0113 set? | Go to DTC P0113 | Go to Step 3
3 |

1. Turn OFF the ignition.
2. Disconnect the IAT sensor. Refer to Intake Air Temperature Sensor Replacement .
3. Inspect for poor connection at the harness connector of the IAT sensor. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
4. Repair connector as necessary. Refer to Connector Repairs or Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 8

Go to Step 4

4 |

1. Test the IAT signal circuit between the IAT sensor and the PCM for and intermittent open. Refer to Circuit Testing in Wiring Systems.
2. Repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 8

Go to Step 5

5 |

1. Test the IAT signal circuit between the IAT sensor and the PCM for an intermittent short to a separate voltage source. Refer to Circuit Testing in Wiring Systems.
2. Repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 8

Go to Step 6

6 |

1. Test the low reference circuit for and intermittent open.
2. Repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 8

Go to Step 7

7 |

1. Disconnect the PCM connector at the PCM. Refer to Powertrain Control Module Replacement .
2. Inspect for poor connections at the harness connector of the PCM.
3. Repair connector as necessary. Refer to Connector Repairs or Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 8

Go to Intermittent Conditions

8 |

1. Use the scan tool to clear the DTC's.
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 9

Go to Step 2

9 | 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