Circuit Description
The intake air temperature (IAT) sensor is a variable resistor. The IAT sensor has a signal circuit and a low reference circuit. The IAT sensor measures the temperature of the air entering the engine. The powertrain control module (PCM) supplies 5 volts to the IAT signal circuit and a ground for the IAT low reference circuit. When the IAT sensor is cold, the sensor resistance is high. When the air temperature increases, the sensor resistance decreases. With high sensor resistance, the PCM detects a high voltage on the IAT signal circuit. With lower sensor resistance, the PCM detects a lower voltage on the IAT signal circuit. If the PCM detects an excessively high IAT signal voltage, indicating a low temperature, DTC P0113 sets.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P0112 Intake Air Temperature (IAT) Sensor Circuit High Voltage
Conditions for Running the DTC
| • | DTCs P0117, P0118, P0125, P0502, P0503 are not set. |
| • | The engine run time is more than 5 minutes. |
| • | The vehicle speed sensor (VSS) indicates that vehicle speed is less than 24 km/h (15 mph). |
| • | DTC P0113 runs continuously when the above conditions are met. |
Conditions for Setting the DTC
The PCM detects that the IAT sensor parameter is less than -39°C (-38°F) for more than 6 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. |
Test Description
The number below refers to the step number on the diagnostic table.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics Connector End View Reference: Powertrain Control Module Connector End Views or Engine Controls Connector End Views | ||||
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | |
2 |
Is the IAT sensor parameter less than the specified value? | -39°C (-38°F) | Go to Step 4 | Go to Step 3 |
3 |
Did the DTC fail this ignition? | -- | Go to Step 4 | Go to Testing for Intermittent Conditions and Poor Connections |
4 |
Is the voltage more than the specified value? | 5.2 V | Go to Step 5 | Go to Step 6 |
5 |
Important: The sensor may be damaged if the circuit is shorted to a voltage source. Test the signal circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 15 | Go to Step 12 |
Is the IAT sensor parameter more than the specified value? | 128°C (262°F) | Go to Step 10 | Go to Step 7 | |
7 |
Is the IAT sensor parameter more than the specified value? | 128°C (262°F) | Go to Step 9 | Go to Step 8 |
8 | Test the signal circuit of the IAT sensor for an open circuit or high resistance. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 15 | Go to Step 12 |
9 | Test the IAT sensor low reference circuit for high resistance or an open. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 15 | Go to Step 12 |
10 | Test the IAT signal circuit for a short to any 5-volt reference circuit. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 15 | Go to Step 11 |
11 |
Important: The sensor may be damaged if the circuit is shorted to a voltage source. Test for an intermittent and for a poor connection at the IAT sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | -- | Go to Step 15 | Go to Step 13 |
12 | Test for an intermittent and for a poor connection at the powertrain control module (PCM). Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | -- | Go to Step 15 | Go to Step 14 |
13 | Replace the IAT sensor. Refer to Intake Air Temperature Sensor Replacement . Did you complete the replacement? | -- | Go to Step 15 | -- |
14 | Replace the PCM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 15 | -- |
15 |
Did the DTC fail this ignition? | -- | Go to Step 2 | Go to Step 16 |
16 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | -- | System OK | |
