Circuit Description
The intake air temperature (IAT) sensor uses a thermistor in order to control the signal voltage to the powertrain control module (PCM). The PCM supplies a 5-volt reference and a ground to the sensor. When the air is cold the resistance is high, and the IAT signal voltage will be high. If the intake air is warm, the resistance is low, and the IAT signal voltage will be low.
Conditions for Running the DTC
| • | DTCs P0117, P0118, P0125, P0502, or P0503 are not set. |
| • | The engine run time is more than 320 seconds. |
| • | The vehicle speed sensor (VSS) indicates that vehicle speed is more than 24 km/h (15 mph). |
Conditions for Setting the DTC
The IAT sensor signal voltage indicates that the IAT is more than 128°C (262°F) for 6.25 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 the vehicle is at the ambient temperature, compare the IAT sensor to the engine coolant temperature (ECT) sensor. The IAT sensor and the ECT sensor temperature readings should be relatively close to each other. |
| • | Use the Temperature vs. Resistance table in order to evaluate the possibility of a skewed sensor. Refer to Temperature Versus Resistance . |
| • | For an intermittent, refer to Intermittent Conditions . |
Test Description
The numbers below refer to step numbers on the diagnostic table.
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This step simulates a DTC P0113 condition. If the scan tool displays the specified value, the IAT signal circuit and the PCM are OK.
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The replacement PCM must be programmed and the crankshaft position system variation learn procedure must be preformed.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics | ||||
1 | Did you perform the Diagnostic System Check-Engine Controls? | -- | Go to Step 2 | |
2 | Turn ON the ignition, with the engine OFF. Is the IAT more than the specified value? | 128°C (262°F) | Go to Step 4 | Go to Step 3 |
3 |
Is the IAT more than the specified value? | 128°C (262°F) | Go to Step 4 | Go to Diagnostic Aids |
Is the IAT less than the specified value? | -30°C (-22°F) | Go to Step 5 | Go to Step 6 | |
5 |
Did you complete the repair? | -- | Go to Step 11 | -- |
6 |
Does the test lamp illuminate? | -- | Go to Step 7 | Go to Step 9 |
7 |
Does the test lamp illuminate? | -- | Go to Step 8 | Go to Step 9 |
8 | Repair the short to ground in the IAT sensor signal circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 11 | -- |
9 | Inspect for a poor connection at the PCM. If a problem is found, repair as necessary. Did you find and correct the condition? | -- | Go to Step 11 | Go to Step 10 |
Replace the PCM. Refer to Powertrain Control Module Replacement . Did you complete the repair? | -- | Go to Step 11 | -- | |
11 |
Does the DTC run and pass? | -- | Go to Step 12 | Go to Step 2 |
12 | With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? | -- | System OK | |
