For 1990-2009 cars

### Circuit Description

The intake air temperature (IAT) sensor uses a thermistor to control the signal voltage to the powertrain control module (PCM). The PCM supplies a 5-volt reference and a ground to the sensor. When the air is cold, the resistance is high, and the IAT signal voltage will be high. If the intake air is warm, the resistance is low, and the IAT signal voltage will be low.

### Conditions for Running the DTC

• | The engine run time is more than 320 seconds.

• | The engine coolant temperature (ECT) is more than -40°C (-40°F).

• | The vehicle speed sensor indicates that the vehicle speed is less than 24 km/h (15 mph).

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

### Conditions for Setting the DTC

The IAT sensor signal voltage indicates that the IAT is less than -40°C (-40°F) for 3.125 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

• | If the vehicle is at the ambient temperature, compare the IAT sensor reading to the ECT sensor reading. The readings should be relatively close to each other.

• | Use the Temperature vs. Resistance table in order to evaluate the possibility of a skewed sensor. Refer to Temperature Versus Resistance .

• | For an intermittent, refer to Intermittent Conditions .

• | If a short to a separate 5-volt source occurs, this DTC may set. If this is found to be the problem, a continuity test to all other PCM circuits will be necessary to diagnose the specific circuit. Refer to Testing for Continuity in Wiring Systems.

### 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 Intake Air Temperature 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 ignition positive voltage, the fuse in the jumper will open, indicating a short in the signal circuit.

4. Reprogram the replacement PCM, and perform the Crankshaft Position System Variation Learn procedure.

#### 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 (-34°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 scan tool indicate DTC P0113 failed this ignition?

--

Go to Step 4

Go to Diagnostic Aids

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 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 | Important: If the IAT circuit is shorted to 12 volts, the IAT sensor may be damaged. Test the signal circuit of the IAT sensor for a short to voltage. Refer to Circuit Testing and 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 for an open. Refer to Circuit Testing and 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 Circuit Testing and 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 Wiring 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 Wiring 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 a 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 14

Go to Step 2

14 | 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