Circuit Description
The intake air temperature (IAT) sensor is a thermistor which measures the temperature of the air entering the engine. The 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 less causing the PCM to monitor a lower voltage. DTC P1111 will set when the PCM detects an intermittently high signal voltage on the intake air temperature sensor signal circuit.
Conditions for Running the DTC
| • | No active engine coolant temperature (ECT) sensor, mass air flow (MAF) sensor or vehicle speed sensor (VSS) DTCs present |
| • | The engine has been running for over 3 minutes. |
| • | The engine coolant temperature is more than 60°C (140°F). |
| • | The vehicle speed is less than 35 mph. |
Conditions for Setting the DTC
The IAT signal voltage intermittently indicates an intake air temperature of less than -38°C (-37°F).
Action Taken When the DTC Sets
| • | The PCM will not illuminate the malfunction indicator lamp (MIL). |
| • | The PCM will store the conditions which were present when the DTC set as Failure Records data only. This information will not be stored as Freeze Frame data. |
Conditions for Clearing the MIL/DTC
| • | A history DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction. |
| • | The DTC can be cleared by using the scan tool. |
Diagnostic Aids
Check for the following conditions:
| • | A faulty connection at the PCM or the sensor--Inspect the harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and faulty terminal to wire connections. Use a corresponding mating terminal to test for proper terminal tension. |
| • | Inspect the wiring harness for damage. If the harness appears to be OK, observe the IAT display on the scan tool while moving the connectors and wiring harnesses related to the IAT sensor. A change in the IAT display will indicate the location of the malfunction. |
| • | A skewed or mis-scaled IAT sensor, refer to Temperature Versus Resistance . |
Reviewing the Failure Records vehicle mileage since the diagnostic test last failed may help determine how often the condition that caused the DTC to be set occurs. This may assist in diagnosing the condition.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
1 | Did you perform the Powertrain On Board Diagnostic (OBD) System Check? | -- | ||
2 | With a scan tool, select Diagnostic Trouble Codes (DTC). Is DTC P0113 also set? | -- | Go to DTC P0113 Intake Air Temperature (IAT) Sensor Circuit High Voltage | |
3 | Is DTC P1106, P1115, and/or P1121 also set? | -- | ||
4 | Inspect for a faulty ground circuit connection 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? | -- | ||
5 | Inspect for a faulty signal circuit connection at the IAT sensor. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems. Did you find and correct the condition? | -- | ||
6 | Test the signal circuit of the IAT sensor for an intermittent open. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | ||
7 | Test the signal circuit of the IAT sensor for an intermittent short to voltage. Refer to Testing for Intermittent Conditions and Poor Connections and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | ||
8 | Inspect for a faulty sensor ground circuit connection 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? | -- | ||
9 | Test the ground circuit of the IAT sensor for an intermittent open or a faulty splice. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Diagnostic Aids | |
10 |
Does the DTC reset? | -- | System OK |
