Circuit Description
The intake air temperature (IAT) sensor is a thermistor which measures the temperature of the air entering the engine. The powertrain control module (PCM) applies 5 volts through a pull up resistor. When the intake air is cold, the sensor resistance is high and the PCM will monitor a high signal voltage on the IAT sensor signal circuit. As the intake air warms, the sensor resistance becomes lower causing the PCM to monitor a lower voltage. If the PCM detects an excessively low IAT sensor signal voltage, high temperature indicated, DTC P0112 will set.
Conditions for Running the DTC
| • | DTC's P0101, P0102, P0103, P0117, P0118, P0125, P0128, P0502, P0503, P1114 and P1115 are not set |
| • | The engine has been running for more than 10 seconds. |
| • | The vehicle speed is more than 25 mph. |
Conditions for Setting the DTC
| • | The IAT signal voltage indicates an intake air temperature that is more than 135°C (275°F). |
| • | The above conditions are present for at least 20 seconds. |
Action Taken When the DTC Sets
| • | The PCM illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle 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 PCM stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the PCM records the operating conditions at the time of the failure. |
| • | The PCM writes the conditions to the Freeze Frame and updates the Failure Records. |
Conditions for Clearing the MIL/DTC
| • | The PCM will turn OFF the malfunction indicator lamp (MIL) during the third consecutive trip in which the diagnostic has run and passed. |
| • | The history DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction. |
| • | The DTC can be cleared by using a scan tool. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
Verifies that the fault is present.
-
If DTC P0112 can be repeated only by duplicating the Failure Records conditions. Refer to the Temperature vs Resistance table. The 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 shorted above or below a certain temperature. If this is the case, replace the IAT sensor. If the IAT sensor appears to be OK, the fault is intermittent refer to Diagnostic Aids.
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 scan tool indicate the IAT parameter is more than specified value? | 135°C (275°F) | Go to Step 4 | Go to Step 3 | |
Does scan tool indicate DTC P0112 failed this ignition? | -- | Go to Step 4 | Go to Intermittent Conditions | |
4 |
Does the scan tool indicate the IAT parameter is less than the specified value? | -37°C (-35°F) | Go to Step 6 | Go to Step 5 |
5 |
Did you find and correct the condition? | -- | Go to Step 8 | Go to Step 7 |
6 | Replace the IAT sensor. Refer to Intake Air Temperature Sensor Replacement . Did you complete the replacement? | -- | Go to Step 8 | -- |
7 | Replace the PCM. Refer to Powertrain Control Module Replacement . Did you complete the replacement? | -- | Go to Step 8 | -- |
8 |
Does the DTC set? | -- | Go to Step 2 | System OK |
