Circuit Description
The intake air temperature (IAT) sensor is a thermistor which measures the temperature of the air entering the engine. The PCM applies 5 volts through a pull-up resistor to the IAT sensor. When the intake air is cold, the sensor resistance is high and the PCM will monitor a high signal voltage on the IAT signal circuit. If the intake air is warm, the sensor resistance is lower causing the PCM to monitor a lower voltage. DTC P0112 will set when the PCM detects an excessively low signal voltage on the intake air temperature sensor signal circuit.
Conditions for Setting the DTC
| • | No ECT sensor, MAF sensor or VSS DTCs present. |
| • | The engine has been running for over 10 seconds. |
| • | Vehicle speed is greater than 40 km/h (25 mph). |
| • | IAT signal voltage indicates an intake air temperature greater than 130°C (266°F). |
| • | The above conditions are present for at least 20 seconds. |
Action Taken When the DTC Sets
| • | The PCM will illuminate the malfunction indicator lamp (MIL) during the second consecutive trip in which the diagnostic test has been run and failed. |
| • | The PCM will store conditions which were present when the DTC set as Freeze Frame/Failure Records data. |
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. |
Diagnostic Aids
Check for the following conditions:
| • | A faulty connection at the PCM--Inspect the harness connectors for backed out terminals, improperly formed or damaged terminals, and faulty terminal to wire connections. Use a corresponding mating terminal to test for proper terminal tension. |
| • | Inspect the wiring harness for damage. If the harness appears to be OK, observe the MAP display on the scan tool while moving connectors and wiring harnesses related to the sensor. A change in the display will indicate the location of the malfunction. |
If DTC P0112 cannot be duplicated, the information included in the Fail Records data can be useful in determining vehicle mileage since the DTC was last set.
Test Description
The number below refers to the step number on the diagnostic table.
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Verifies that the fault is present.
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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 at more than or less than 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.
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This vehicle is equipped with a PCM which utilizes an electrically erasable programmable read-only memory (EEPROM). When the PCM is replaced, the new PCM must be programmed.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
1 | Did you perform the Powertrain On Board Diagnostic (OBD) System Check? | -- | ||
Is the IAT parameter more than the specified value? | 135°C (275°F) | |||
Does the scan tool indicate DTC P0112 failed this ignition? | -- | Go to Diagnostic Aids | ||
4 |
Is the IAT parameter less than the specified value? | -37°C (-34°F) | ||
5 |
Did you find and correct the condition? | -- | ||
6 | Replace the IAT sensor. Refer to Intake Air Temperature Sensor Replacement . Did you complete the replacement? | -- | -- | |
|
Important: : The replacement PCM must be programmed. Replace the PCM. Refer to Powertrain Control Module Replacement/Programming . Did you complete the replacement? | -- | -- | ||
8 |
Does the DTC reset? | -- | System OK |
