Circuit Description
The intake air temperature (IAT) sensor is a thermistor that controls signal voltage to the powertrain control module (PCM). When the air is cold, the sensor resistance is high, therefore the PCM will see a high signal voltage. As air warms, sensor resistance becomes less and voltage drops.
Conditions for Running the DTC
| • | The PCM performs this diagnostic trouble code (DTC) diagnostic continuously. |
| • | The engine coolant temperature (ECT) is less than 42.5°C (109°F). |
Conditions for Setting the DTC
| • | The Intake air temperature is more than or equal to 151°C (303°F). |
| • | All of the diagnostic set conditions were met for 2 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
Check harness routing for a potential short to ground in the signal circuit. Refer to Symptoms - Engine Controls . The scan tool displays intake air temperature in degrees centigrade. A skewed sensor could result in poor driveability complaints. Refer to Temperature Versus Resistance .
An intermittent may be caused by any of the following conditions:
| • | A poor connection |
| • | Rubbed through wire insulation |
| • | A broken wire inside the insulation |
Thoroughly check any circuitry that is suspected of causing the intermittent complaint. Refer to Testing for Electrical Intermittents in Wiring Systems.
If a repair is necessary, then refer to Wiring Repairs or Connector Repairs in Wiring Systems.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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This step determines if DTC P0112 is a hard failure or an intermittent condition.
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This test will determine if the PCM can recognized an open sensor.
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This step will determine if the problem is a short to ground or a malfunctioning PCM.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics | ||||
1 | Did you perform the Diagnostic System Check-Engine Controls? | -- | Go to Step 2 | |
Does the IAT measure more than or equal to the specified value? | 151°C (303°F) | Go to Step 3 | Go to Step 5 | |
Does the IAT display a temperature less than the specified value? | -30 °C (-22 °F) | Go to Step 7 | Go to Step 4 | |
Does the resistance measure at the specified value? | ∞ | Go to Step 8 | Go to Step 6 | |
5 | The DTC is intermittent. If no additional DTCs are stored, refer to Diagnostic Aids. If additional DTCs were stored, refer to those tables. Are any additional DTCs stored? | -- | Go to Diagnostic Aids | |
6 | Repair the short to ground in the IAT signal circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 9 | -- |
7 | Replace the IAT sensor. Refer to Intake Air Temperature Sensor Replacement . Did you complete the replacement? | -- | Go to Step 9 | -- |
8 | Replace the PCM. Refer to Powertrain Control Module Replacement . Did you complete the replacement? | -- | Go to Step 9 | -- |
9 |
Does the scan tool indicate the diagnostic passed? | -- | Go to Step 10 | Go to Step 2 |
10 | Does the scan tool display any additional undiagnosed DTCs? | -- | System OK | |
