Circuit Description
The intake air temperature (IAT) sensor is a thermistor that controls the signal voltage to the powertrain control module (PCM). When the air is cold, the sensor resistance is high, and the PCM will see a high signal voltage. As the air warms, the sensor resistance becomes less and the voltage drops.
Conditions for Running the DTC
The engine coolant temperature is less than 42.5°C (109°F).
Conditions for Setting the DTC
| • | The intake air temperature is more than or equal to 152°C (304°F). |
| • | The 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 the harness routing for a potential short to ground in the signal circuit. The scan tool displays the intake air temperature in degrees Celsius. Refer to Symptoms - Engine Controls . A skewed sensor could result in poor driveability complaints. Refer to Temperature Versus Resistance .
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 recognize an open sensor.
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This step will determine if the condition is a malfunctioning PCM or if the signal wire is shorted to ground. The normal resistance across the IAT sensor connector harness is 4,000-5,000 ohms.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics | ||||
1 | Did you perform the Diagnostic System Check-Engine Controls? | -- | Go to Step 2 | |
Is the IAT display 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 that is colder than or equal to the specified value? | -30°C (-22°F) | Go to Step 7 | Go to Step 4 | |
Does the DMM indicate OL? | -- | Go to Step 8 | Go to Step 6 | |
5 | The DTC is intermittent. If no additional DTCs are stored, refer to Diagnostic Aids. If any additional DTCs were stored, refer to those tables. Are there 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 | |
