Circuit Description
The intake air temperature (IAT) sensor is a thermistor which measures the temperature of the air that enters the engine. The powertrain control module (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. The PCM will set a diagnostic trouble code (DTC) if an excessively high IAT sensor signal voltage is detected.
Conditions for Running the DTC
| • | DTCs P0117, P0118, P0125, P0128, P0502, P0503, P1114, or P1115 are not set. |
| • | The engine has been running for over 3 minutes. |
| • | The vehicle speed is less than 8.5 km/h (5 mph). |
| • | The mass air flow (MAF) is less than 8 g/s. |
| • | The engine coolant temperature is more than 60°C (140°F). |
Conditions for Setting the DTC
| • | The PCM detects that the IAT sensor temperature is less than -34°C (-30°F) for more than 20 seconds. |
| • | The above condition is present for at least 110 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 a short to a separate 5-volt source occurs this DTC may set. If this is found to be a problem, a continuity test to all other PCM circuits will be necessary to diagnose the specific circuit.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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This step verifies that the fault is present.
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If DTC P0113 can be repeated only by duplicating the Failure Records conditions, use the Temperature vs Resistance table in order to test the IAT sensor at various temperatures. This procedure will evaluate the possibility of a shifted sensor that may be open 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 Intermittent Conditions.
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During this test use a fused jumper. If the IAT signal circuit is shorted to the battery or to the ignition positive voltage, the fuse in the jumper will open. This indicates 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 | |
Is the IAT sensor less than the specified value? | -37°C (-34°F) | Go to Step 4 | Go to Step 3 | |
Does the DTC set? | -- | Go to Step 4 | Go to Diagnostic Aids | |
4 |
Is the IAT sensor more than the specified value? | 135°C (275°F) | Go to Step 6 | Go to Step 5 |
Is the IAT sensor more than the specified value? | 135°C (275°F) | Go to Step 7 | Go to Step 8 | |
6 | Test the IAT sensor signal circuit 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 IAT sensor ground circuit for a high resistance or 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 |
8 | Test the IAT sensor signal circuit 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 | Test for an intermittent and for a poor connection at the PCM. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 13 | Go to Step 12 |
10 | Test for an intermittent and for a poor connection at the IAT sensor. Refer to Testing for Intermittent Conditions and Poor Connections 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 | |
