Circuit Description
The intake air temperature (IAT) sensor is a thermistor that controls signal voltage to the 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 DTC diagnostic continuously. |
| • | 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 151°C (303°F). |
| • | All of the diagnostic set conditions were met for 2 seconds. |
Action Taken When the DTC Sets
| • | The PCM illuminates the malfunction indicator lamp (MIL) on the second consecutive drive trip that the diagnostic runs and fails. |
| • | The PCM records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the Failure Records will store this information. If the diagnostic reports a failure on the second consecutive drive trip, the Freeze Frame records the operating conditions at the time of failure and updates the Failure Records. |
Conditions for Clearing the MIL/DTC
| • | The PCM will turn the MIL off after 3 consecutive trips without a fault condition. |
| • | A history DTC clears after 40 consecutive warm-up cycles, if this or any other emission related diagnostic does not report any failures. |
| • | The scan tool Clear Info function was used. |
Diagnostic Aids
Check harness routing for a potential short to ground in the signal circuit. Refer to Symptoms . 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.
-
This step determines if P0112 is a hard failure or an intermittent condition.
-
This test will determine if the PCM can recognized an open sensor.
-
This step will determine if the problem is a short to ground or a malfunctioning PCM.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
1 |
Important: Before clearing any DTCs, use the scan tool Capture Info to save freeze frame and failure records for reference, as the scan tool loses data when using the Clear Info function. Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | ||
Is the IAT display greater than or equal to the specified value? | 151°C (303°F) | |||
Does the IAT display a temperature colder than or equal to the specified value? | -30°C (-22°F) | |||
Is the resistance at the specified value? | ∞ | |||
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 the Applicable DTC Table | Go to Diagnostic Aids |
6 | Repair the short to ground in the IAT signal circuit. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | -- | |
7 | Replace the IAT sensor. Refer to Intake Air Temperature Sensor Replacement . Is the action complete? | -- | -- | |
8 |
Important: The new PCM must be programmed. Refer to Powertrain Control Module Replacement/Programming . Replace the PCM. Is the action complete? | -- | -- | |
9 |
Does the scan tool indicate the diagnostic Passed? | -- | ||
10 | Does the scan tool display any additional undiagnosed DTCs? | -- | Go to the Applicable DTC Table | System OK |
