P0111

DTC P0111: Intake Air Temperature (IAT) Sensor Performance

Circuit Description
The Intake Air Temperature (IAT) Sensor uses a thermistor to control the signal voltage to the Engine Control Module (ECM). The ECM supplies a 5 volt reference voltage and a ground to the sensor. When the air is cold, the resistance is high; therefore IAT sensor signal voltage will be high. If the intake air is warm, resistance is low; therefore the IAT sensor signal voltage will below.

Conditions for Setting the DTC
- No disabling faults present.
- Engine is running.
- Soak time is 480 minutes or greater.
- Intake air temperature (IAT) is stored on previous trip.

(Skewed Low Test)
- Startup coolant temperature is higher than -20 °C (-4 °F).
- Vehicle speed is higher than 40km/h.
- Airflow is greater than 15g/sec.
- Difference between startup ECT and startup IAT is greater than 20 °C (68 °F).

(Skewed High Test)
- Vehicle speed is higher than 40 km/h.
- Airflow is greater than 15 g/sec.
- Intake air temperature (IAT) is higher than threshold based on startup coolant temperature.

Action Taken When the DTC Sets
- The Malfunction Indicator Lamp (MIL) will illuminate.
- The ECM will record operating conditions at the time the diagnostic fail. This information will be stored in the Freeze Frame and Failure Records buffers.
- A history DTC is stored.

Conditions for Clearing the MIL/DTC
- The MIL will turn OFF after four consecutive ignition cycles in which the diagnostic runs without a fault.
- A history DTC will clear after 40 consecutive warm up cycles without a fault.
- The DTC(s) can be cleared by using the scan tool.
- Disconnecting the ECM battery feed for more than 10 seconds.

Diagnostic Aids
Check for a faulty electrical connection to the ECM. If the vehicle is at ambient temperature, compare the IAT sensor to the engine coolant temperature (ECT) sensor. The IAT sensor and the ECT sensor should be relatively close to each other. Use the temperature vs. Resistance Values table to evaluate the possibility of a skewed sensor. Refer to Temperature VS Resistance.

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Troubleshooting