Circuit Description
The intake air temperature (IAT) sensor is a thermistor. The powertrain control module (PCM) supplies the IAT sensor a reference voltage on the IAT sensor signal circuit and a ground circuit. When the IAT sensor is cold, the resistance is high. The IAT sensor signal voltage remains near the supplied voltage and decreases the signal voltage as the sensor warms. The control module monitors the IAT sensor signal circuit in order to calculate the temperature of the air entering the engine.
This DTC is designed to detect an IAT sensor signal voltage higher than possible in a normally operating IAT system.
Conditions for Running the DTC
| • | The engine run time is more than 320 seconds. |
| • | The vehicle speed sensor indicates that vehicle speed is less than 15 mph (24 km/h). |
| • | DTCs 117, 118, 125, 502, 503 are not set. |
Conditions for Setting the DTC
The IAT sensor signal voltage indicates that the intake air temperature is less than -40°C (-40°F) for 3 seconds.
Action Taken When the DTC Sets
| • | The malfunction indicator lamp (MIL) illuminates after 2 consecutive ignition cycles with the malfunction present. |
| • | The PCM records the operating conditions at the time the diagnostic fails. The Freeze Frame and Failure Records buffers stores this information. |
| • | A history DTC is stored. |
| • | The PCM will default to 60°C (140°F) for intake air temperature. The scan tool will not show the defaulted value. |
Conditions for Clearing the MIL/DTC
| • | The MIL will turn OFF after 3 consecutive ignition cycles in which the diagnostic runs without a fault. |
| • | A history DTC will clear after 40 consecutive warm up cycles without a fault. |
| • | A scan tool can clear the DTCs. |
Diagnostic Aids
| • | When the vehicle is at ambient temperature, compare the IAT sensor to the ECT sensor. The IAT sensor and the ECT sensor should be relatively close to each other. |
| • | Use the Temperature vs Resistance Values Table below to evaluate the possibility of a skewed sensor. Refer to Temperature Versus Resistance . |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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The Powertrain OBD System Check prompts you to complete some of the basic checks and to store the Freeze Frame and Failure Records data on the scan tool if applicable. This creates an electronic copy of the data captured when the malfunction occurred. The scan tool stores this data for later reference.
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This step simulates a DTC P0112. If the PCM senses the change, the PCM and wiring are OK.
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Reprogram the replacement PCM and perform the Crankshaft Position System Variation Learn Procedure. Refer to the latest Techline information for PCM programming.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | |||
2 |
Is the IAT sensor value less than the specified value? | -30° C (-22° F) | ||
3 |
Does the scan tool display an IAT sensor value more than the specified value? | 130° C (266° F) | ||
Jumper the IAT sensor signal circuit to a ground. Does the scan tool display an IAT sensor value more than the specified value? | 130° C (266° F) | |||
5 | Check the voltage between the IAT sensor signal circuit and a ground using a DMM . Is the voltage more than the specified value? | 5.20 V | ||
6 | The DTC is intermittent. Are any additional DTCs stored? | -- | Go to applicable DTC table | Go to Diagnostic Aids |
7 | Inspect the IAT sensor harness connector and the PCM connector for poor connection or incorrect terminal tension. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems. Did you find a condition? | -- | ||
8 | Inspect the IAT sensor ground circuit for an open or poor connection between the IAT sensor and the PCM. Did you find a condition? | -- | ||
9 | Inspect the sensor signal circuit for an open or poor connection between the IAT sensor and the PCM. Did you find a condition? | -- | ||
10 | Repair the short to voltage in the IAT sensor signal circuit. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | -- | |
11 | Repair the circuit as necessary. Refer to Wiring Repairs or Connector Repairs in Wiring Systems. Is the action complete? | -- | -- | |
12 | Replace the IAT sensor. Refer to Intake Air Temperature Sensor Replacement . Is the action complete? | -- | -- | |
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Important: The replacement PCM must be programmed. Replace the PCM. Refer to Powertrain Control Module Replacement/Programming . Is the action complete? | -- | -- | ||
14 |
Does the scan tool indicate the diagnostic Passed? | -- | ||
15 | Does the scan tool display any additional, undiagnosed DTCs? | -- | Go to applicable DTC table | System OK |
