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 excessively high IAT signal voltage, indicating a low temperature, DTC P0113 sets.

### Conditions for Running the DTC

• | DTCs P0116, P0117, P0118, P0125, P0128, P0502, or P0503 are not set.

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

• | The vehicle speed sensor (VSS) indicates that vehicle speed 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).

### 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.

### Diagnostic Aids

• | When the vehicle is at ambient temperature the IAT sensor and ECT sensor temperatures should be relatively close to each other. Refer to Temperature Versus Resistance .

• | If a short to a separate 5-volt source occurs this DTC may set. If this condition exists, a continuity test to all other PCM 5-volt reference circuits will be necessary.

• | If an intermittent condition is suspected, refer to Intermittent Conditions .

### Test Description

The number below refers to the step number on the diagnostic table.

1. This step tests for the proper operation of the circuit in the low voltage range. If the fuse in the jumper opens when you perform this test, the signal circuit is shorted to voltage.

#### DTC P0113

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 |

1. Install a scan tool.
2. Turn ON the ignition, with the engine OFF.
3. Observe the IAT sensor temperature with a scan tool.

Is the IAT sensor temperature less than the specified value?

-38°C (-36°F)

Go to Step 4

Go to Step 3

3 |

1. Observe the Freeze Frame/Failure Records data for this DTC.
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, or as close to the Freeze Frame/Failure Records data that you observed.

Does the DTC reset?

--

Go to Step 4

Go to Diagnostic Aids

4 |

1. Turn OFF the ignition.
2. Disconnect the IAT sensor. Refer to Intake Air Temperature Sensor Replacement .
3. Connect a DMM between the signal circuit and the low reference circuit of the IAT sensor harness.
4. Turn ON the ignition.

Does the DMM voltage measure more than the specified value?

5 V

Go to Step 5

Go to Step 6

5 | Important: The sensor may be damaged if the circuit is shorted to a voltage source.

1. Test the signal circuit for a short to voltage. 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 14

Go to Diagnostic Aids

6 |

1. Turn OFF the ignition.
2. Disconnect the IAT sensor. Refer to Intake Air Temperature Sensor Replacement .
3. Connect a 3-amp fused jumper wire between the signal circuit of the IAT sensor and the low reference circuit at the IAT sensor. Refer to Using Fused Jumper Wires in Wiring Systems.
4. Turn ON the ignition, with the engine OFF.
5. Observe the IAT sensor temperature with a scan tool.

Is the IAT sensor temperature more than the specified value?

128°C (262°F)

Go to Step 10

Go to Step 7

7 |

1. Turn OFF the ignition.
2. Connect a 3-amp fused jumper wire between the signal circuit of the IAT sensor and a known good ground.
3. Turn ON the ignition, with the engine OFF.
4. Observe the IAT sensor temperature with a scan tool.

Is the IAT sensor temperature more than the specified value?

128°C (262°F)

Go to Step 9

Go to Step 8

8 | Test the signal circuit of the IAT sensor for an open circuit or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 14 | Go to Step 11
9 | Test the IAT sensor low reference circuit for high resistance or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 14 | Go to Step 11
10 | Important: If a short to a separate voltage source occurs this DTC may set and damage the IAT sensor. If this is found to be the condition, a continuity test to all other PCM circuits will be necessary to diagnose the specific fault. Inspect for poor connections at the harness connector of the IAT sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 14

Go to Step 12

11 |

1. Inspect for poor connections at the harness connector of the PCM. Refer to Powertrain Control Module Replacement .
2. Repair the connections as necessary. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 14

Go to Step 13

12 | Replace the IAT sensor. Refer to Intake Air Temperature Sensor Replacement . Did you complete the replacement? | -- | Go to Step 14 | --
13 | Replace the PCM. Refer to Powertrain Control Module Replacement . Did you complete the replacement? | -- | Go to Step 14 | --
14 |

1. Use the scan tool 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 15

Go to Diagnostic Aids

15 | 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