Circuit Description
The intake air temperature (IAT) sensor is a thermistor. The control module supplies the IAT sensor a reference voltage on the IAT sensor signal circuit and a ground circuit. When the IAT sensor resistance is high, indicating a cold sensor, 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 diagnostic trouble code (DTC) is designed to detect an IAT sensor signal voltage higher than the possible range of a normally operating IAT sensor.
Conditions for Running the DTC
| • | DTCs P0101, P0102, P0103, P0117, P0118, P0125, P0502, P0503, P1114, and P1115 are not set. |
| • | The vehicle speed is below 3 km/h (2 mph). |
| • | The mass air flow (MAF) is less than 250 g/s. |
| • | The coolant temperature is above 85°C (184°F). |
| • | The engine has been running for more than 100 seconds. |
Conditions for Setting the DTC
The IAT sensor temperature is less than -35°C (-31°F) for more than 5 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
The IAT sensor indicates the temperature of the ambient air which is entering the throttle body. The IAT sensor temperature should read very close to the temperature of the outside air. The IAT sensor temperature should rise gradually as the engine warms up and the underhood temperature increases. If DTC P1111 is set, the problem is intermittent. Check for an open in the IAT sensor circuit. This may be accomplished by moving the PCM harness at various locations and monitoring IAT temperature or IAT voltage on the scan tool. If the voltage varies, look for an open in the area of the harness that caused the variance. Also, a sensor may become skewed or mis-scaled. Refer to Temperature Versus Resistance .
An intermittent may be caused by any of the following conditions:
| • | A poor connection |
| • | Rubbed through wire insulation |
| • | A broken wire inside the insulation |
Thoroughly inspect any circuitry that is suspected of causing the intermittent complaint. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
If a repair is necessary, refer to Wiring Repairs or Connector Repairs in Wiring Systems.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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If the IAT sensor temperature is less than -39°C (-38°F), the conditions for the DTC are still present, and the problem is not intermittent.
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This test will bypass the IAT sensor and will confirm that the IAT signal circuit and the sensor low reference circuit to the PCM are sound. Grounding the signal circuit will provide a low voltage input to the PCM. The PCM should recognize this low voltage and indicate a high IAT temperature.
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This test determines if the IAT sensor signal circuit is okay. If the scan tool does not indicate a high temperature, the IAT signal circuit is open.
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 temperature near the specified value? | -39°C (-38°F) | Go to Step 3 | Go to Step 6 | |
Does the scan tool display an IAT sensor voltage less than the specified value? | 0.82 V | Go to Step 5 | Go to Step 4 | |
Jumper the IAT sensor signal circuit to a ground. Does the scan tool display an IAT sensor temperature more than the specified value? | 139°C (282°F) | Go to Step 8 | Go to Step 9 | |
5 | Check the voltage between the IAT sensor signal circuit and a ground using a DMM. Is the voltage more than the specified value? | 5.2 V | Go to Step 10 | Go to Step 7 |
6 | The DTC is intermittent. Are any additional DTCs stored? | -- | Go to Diagnostic Aids | |
7 | Check the IAT sensor harness connector and the PCM connector for a poor connection. Did you find a problem? | -- | Go to Step 11 | Go to Step 12 |
8 | Check the IAT sensor low reference circuit for an open or poor connection between the IAT sensor and the PCM. Did you find a problem? | -- | Go to Step 11 | Go to Step 13 |
9 | Check the IAT sensor signal circuit for an open or poor connection between the IAT sensor and the PCM. Did you find a problem? | -- | Go to Step 11 | Go to Step 13 |
10 | Repair the short to voltage in the IAT sensor signal circuit. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | Go to Step 14 | -- |
11 | Repair the circuit as necessary. Refer to Wiring Repairs or Connector Repairs in Wiring Systems. Is the action complete? | -- | Go to Step 14 | -- |
12 | Replace the IAT sensor. Refer to Intake Air Temperature Sensor Replacement . Is the action complete? | -- | Go to Step 14 | -- |
13 | Replace the PCM. Refer to Powertrain Control Module Replacement . Is the action complete? | -- | Go to Step 14 | -- |
14 |
Does the scan tool indicate the diagnostic Passed? | -- | Go to Step 15 | Go to Step 2 |
15 | Does the scan tool display any additional undiagnosed DTCs? | -- | System OK | |
