P1111

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 lower 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 ECT sensor, MAF sensor, or VSS DTCs are present
^ The engine has been running for over 3 minutes. Engine coolant temperature is greater than 60°C (140°F).
^ Vehicle speed is less than 56 km/h (35 mph).
^ Mass air flow is less than 12 g/s.

Conditions for Setting the DTC

^ IAT signal voltage intermittently indicates an intake air temperature less than -38°C (-37°F).
^ The condition is present for longer than 20 seconds.

Action Taken When the DTC Sets

^ The PCM will not illuminate the Malfunction Indicator Lamp (MIL).
^ The PCM will store conditions which were present when the DTC set as Fail 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.
^ DTC can be cleared by using the scan tool Clear Info function.

Diagnostic Aids

Check for the following conditions:

^ Poor connection at the PCM.
Inspect harness connectors for backed out terminals improper mating, broken locks, improperly formed or damaged terminals and poor terminal to wire connection.
^ 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 connectors and wiring harnesses related to the IAT sensor. A change in the IAT display will indicate the location of the malfunction.
^ Skewed or mis-scaled IAT Sensor.
Refer to Temperature vs Resistance table. Air Temperature Sensor ( Ambient / Intake )

If DTC P1111 cannot be duplicated, the information included in the Freeze Frame/Fail Records data can be useful in determining vehicle mileage since the DTC was last set.