For 1990-2009 cars

### Circuit Description

The intake air temperature (IAT) sensor is a thermistor which measures the temperature of the air entering the engine. The powertrain control module (PCM) applies 5 volts through a pull-up resistor. When the intake air is cold, the sensor resistance is high, and the PCM will monitor a high signal voltage on the IAT sensor signal circuit. As the intake air warms, the sensor resistance becomes lower, causing the PCM to monitor a lower voltage. If the PCM detects an excessively high IAT sensor signal voltage, a low temperature is indicated, and DTC P0113 will set.

### Conditions for Running The DTC

• | DTCs P0101, P0102, P0103, P0117, P0118, P0125, P0128, P0502, P0503, P1114, or P1115 are not set.

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

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

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

• | The engine run time is more than 3 minutes.

### Conditions for Setting the DTC

• | The IAT signal voltage indicates an intake air temperature that is less than -37°C (-35°F).

• | The above conditions are present for at least 20 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.

### Test Description

The numbers below refer to the step numbers on the diagnostic table.

1. This step verifies that the fault is present.

2. If DTC P0113 can be repeated only by duplicating the Failure Records conditions, the Temperature vs Resistance table may be used to test the IAT sensor at various temperatures in order to evaluate the possibility of a shifted sensor that may be open above or below a certain temperature. If this is the case, replace the IAT sensor. Refer to IAT sensor replacement. If the IAT sensor appears OK, the fault is intermittent. Refer to Diagnostic Aids.

3. Use a fused jumper during this test. If the IAT signal circuit is shorted to battery or to ignition positive voltage, the fuse in the jumper will open, indicating a short in the signal circuit.

#### DTC P0113 - IAT Sensor Circuit High Voltage

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. Turn ON the ignition, with the engine OFF.
2. With a scan tool, observe the IAT parameter.

Does the scan tool indicate the IAT parameter is less than the specified value?

-37°C (-35°F)

Go to Step 4

Go to Step 3

3 |

1. With a scan tool, review and record the Failure Records data.
2. Operate vehicle within the Failure Records conditions as noted.

Does the scan tool indicate that DTC P0113 failed this ignition?

--

Go to Step 4

Go to Intermittent Conditions

4 |

1. Turn OFF the ignition.
2. Disconnect the IAT sensor.
3. Connect a 3 amp fused jumper between the signal circuit of the IAT sensor and the low reference circuit of the IAT sensor.
4. With a scan tool, observe the IAT parameter.

Does the scan tool indicate that the IAT parameter is more than the specified value?

135°C (275°F)

Go to Step 6

Go to Step 5

5 |

1. Jumper the IAT signal circuit to a good ground.
2. With a scan tool, observe the IAT parameter.

Does the scan tool indicate the IAT parameter is more than the specified value?

135°C (275°F)

Go to Step 7

Go to Step 8

6 | Test the signal circuit of the IAT sensor for a short to voltage. Refer to Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 13 | Go to Step 10
7 | Test the low reference circuit of the IAT sensor for a high resistance or an open. Refer to Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 13 | Go to Step 9
8 | Test the signal circuit of the IAT sensor for an open. Refer to Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 13 | Go to Step 9
9 | Inspect for faulty IAT sensor low reference or signal circuit connections at the PCM. 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 13 | Go to Step 12
10 | Inspect for a faulty connections at 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 13 | Go to Step 11
11 | Replace the IAT sensor. Refer to Intake Air Temperature Sensor Replacement . Did you complete the replacement? | -- | Go to Step 13 | --
12 | Replace the PCM. Refer to Powertrain Control Module Replacement . Did you complete the replacement? | -- | Go to Step 13 | --
13 |

1. Use the scan tool in order to clear the DTCs.
2. Operate the vehicle within the Failure Records conditions as noted.

Does the DTC reset?

--

Go to Step 2

System OK