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 warm, the sensor resistance becomes lower, causing the PCM to monitor a lower voltage. If the PCM detects an excessively high IAT sensor signal voltage, a low temperature is indicated, and DTC P0113 will set.
Conditions for Running The DTC
| • | DTCs P0101, P0102, P0103, P0117, P0118, P0125, P0128, P0502, P0503, P1114, or P1115 are not set. |
| • | The vehicle speed is less than 56 km/h (35 mph). |
| • | The mass air flow is less than 12 gm/s. |
| • | The engine coolant temperature is more than 60°C (140°F). |
| • | The engine run time is more than 3 minutes. |
Conditions for Setting the DTC
| • | The IAT signal voltage indicates an intake air temperature that is less than -37°C (-35°F). |
| • | The above conditions are present for at least 20 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. |
Diagnostic Aids
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 in order 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.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
This step verifies that the fault is present.
-
Use a fused jumper during this test. If the IAT signal circuit is shorted to battery or to ignition positive voltage, the fuse in the jumper will open, indicating a short in the signal circuit.
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 less than the specified value? | -37°C (-35°F) | Go to Step 4 | Go to Step 3 | |
3 |
Does the scan tool indicate that DTC P0113 failed this ignition? | -- | Go to Step 4 | Go to Intermittent Conditions |
4 |
Does the scan tool indicate that the IAT parameter is more than the specified value? | 135°C (275°F) | Go to Step 6 | Go to Step 5 |
Does the scan tool indicate the IAT parameter is more than the specified value? | 135°C (275°F) | Go to Step 7 | Go to Step 8 | |
6 | Test the signal circuit of the IAT sensor for a short to voltage. Refer to Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 13 | Go to Step 10 |
7 | Test the low reference circuit of the IAT sensor for a high resistance or an open. Refer to Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 13 | Go to Step 9 |
8 | Test the signal circuit of the IAT sensor for an open. Refer to Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 13 | Go to Step 9 |
9 | Inspect for faulty IAT sensor low reference or signal circuit connections at the PCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 13 | Go to Step 12 |
10 | Inspect for faulty connections at the IAT sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 13 | Go to Step 11 |
11 | Replace the IAT sensor. Refer to Intake Air Temperature Sensor Replacement . Did you complete the replacement? | -- | Go to Step 13 | -- |
12 | Replace the PCM. Refer to Powertrain Control Module Replacement . Did you complete the replacement? | -- | Go to Step 13 | -- |
13 |
Does the DTC run and pass? | -- | Go to Step 14 | Go to Step 2 |
14 | With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? | -- | System OK | |
