Circuit Description
The intake air temperature (IAT) sensor is a thermistor which measures the temperature of the air entering the engine. The PCM applies 5.0 volts through a pull-up resistor to the IAT sensor. When the intake air is cold, the sensor resistance is high and the powertrain control module (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. DTC P1111 will set when the PCM detects an intermittently high signal voltage on the IAT sensor signal circuit.
Conditions for Running the DTC
| • | No active ECT, MAF, or VSS DTCs are set. |
| • | The vehicle speed is less than 56 km/h (35 mph). |
| • | The MAF is less than 12 g/s. |
| • | The ECT is more than 60°C (140°F). |
| • | Engine run time is more than 3 minutes. |
Conditions for Setting the DTC
| • | The IAT signal voltage indicates an intake air temperature intermittently less than -37°C (-35°F). |
| • | The condition is present for up to 5 seconds. |
Action Taken When the DTC Sets
The PCM stores conditions which were present when the DTC set as Failure Records only. This information will not be stored as Freeze Frame Records.
Conditions for Clearing the MIL/DTC
| • | The DTC becomes history when the conditions for setting the DTC are no longer present. |
| • | The history DTC clears after 40 malfunction free warm-up cycles. |
| • | The PCM receives a clear code command from the scan tool. |
Diagnostic Aids
Inspect for the following conditions:
| • | A poor connection at the PCM. Inspect the harness connectors for the following conditions: |
| - | Backed-out terminals |
| - | Improper mating |
| - | Broken locks |
| - | Improperly formed or damaged terminals |
| - | Poor terminal-to-wire connection |
| • | Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems. |
| • | A damaged harness. 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 the wiring harnesses related to the IAT sensor. A change in the IAT display indicates the location of the fault. Refer to Wiring Repairs in Wiring Systems. |
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 (DTCs). Is DTC P0113 also set? | -- | Go to DTC P0113 Intake Air Temperature (IAT) Sensor Circuit High Voltage | |
3 | Are DTCs P1106, P1115, 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 |
