For 1990-2009 cars
Engine Controls Components
Engine Data Sensors
OBD II Symbol Description Notice
Powertrain Control Module Connector End Views
Handling ESD Sensitive Parts Notice
Handling ESD Sensitive Parts Notice

### Circuit Description

The intake air temperature (IAT) sensor uses a thermistor to control the signal voltage to the PCM. The PCM supplies a 5 V 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, 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 vehicle speed sensor indicates that vehicle speed is more than 24 km/h (15 mph).

### Conditions for Setting the DTC

The IAT sensor signal voltage indicates that the intake air temperature is more than 128°C (262°F) for 3.125 seconds.

### Action Taken When the DTC Sets

• | The Malfunction Indicator Lamp (MIL) will illuminate.

• | The PCM will record operating conditions at the time the diagnostic fails. This information will be stored in the Freeze Frame and Failure Records buffers.

• | A history DTC is stored.

• | The coolant fan turns on.

• | The PCM will use a default 60°C (140°F) for the intake air temperature. The scan tool will not the show the defaulted value.

### Conditions for Clearing the MIL/DTC

• | The MIL will turn off after 3 consecutive ignition cycles in which the diagnostic runs without a fault.

• | A history DTC will clear after 40 consecutive warm up cycles without a fault.

• | Use a scan tool to clear the DTCs.

### Diagnostic Aids

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

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

### Test Description

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

1. This step simulates a DTC P0113 condition. If the scan tool displays the specified value, the IAT signal circuit and the PCM are OK.

2. The replacement PCM must be programmed and the Crankshaft Position System Variation Learn procedure must be preformed.

#### DTC P0112-Intake Air Temperature (IAT) Circuit-Low Voltage

Step | Action | Values | Yes | No
--- | --- | --- | --- | ---
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | Go to Step 2 | Go to Powertrain On Board Diagnostic (OBD) System Check
2 | Turn on the ignition, leaving the engine off. Is the IAT more than the specified value? | 128°C (262°F) | Go to Step 4 | Go to Step 3
3 |

1. Review and record the Freeze Frame data.
2. Operate the vehicle within the Freeze Frame conditions and the Conditions for Running the DTC, as specified in the supporting text.

Is the IAT more than the specified value?

128°C (262°F)

Go to Step 4

Go to Diagnostic Aids

4 |

1. Turn off the ignition.
2. Disconnect the IAT sensor connector.
3. Turn on the ignition, leaving the engine off.

Is the IAT less than the specified value?

-30°C (-22°F)

Go to Step 5

Go to Step 6

5 |

1. Turn off the ignition.
2. Replace the IAT sensor. Refer to Intake Air Temperature Sensor Replacement .

Did you complete the repair?

--

Go to Step 11

--

6 |

1. Turn off the ignition.
2. Connect a test lamp to B+.
3. Probe the IAT sensor signal circuit at the IAT sensor connector.

Does the test lamp illuminate?

--

Go to Step 7

Go to Step 9

7 |

1. Turn off the ignition.
2. Disconnect the PCM connector.
3. Connect a test lamp to B+.
4. Probe the IAT sensor signal circuit at the IAT sensor connector.

Does the test lamp illuminate?

--

Go to Step 8

Go to Step 9

8 | Repair the short to ground in the IAT sensor signal circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 11 | --
9 | Inspect for a poor connection at the PCM. If a problem is found, repair as necessary. Did you find and correct the condition? | -- | Go to Step 11 | Go to Step 10
10 | Important:: The replacement PCM must be programmed. Refer to Powertrain Control Module Replacement/Programming . Replace the PCM. Refer to Powertrain Control Module Replacement . Did you complete the repair? | -- | Go to Step 11 | --
11 |

1. Use a scan tool to clear the DTCs.
2. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC reset?

--

Go to Step 2

System OK