Circuit Description

The DTC P0111 Intake Air Temperature (IAT) Sensor Performance diagnostic checks the accuracy of the IAT sensor signal. A thermistor is a resistor whose value varies with the temperature. The electrical resistance of the IAT sensor is high when the intake air temperature is cold, and the resistance is low when the air temperature is warm. The IAT sensor is wired in series with a fixed resistor in the Powertrain Control Module (PCM). The PCM applies 5 volts to the IAT sensor. The PCM monitors the voltage across the IAT sensor and converts the voltage into a temperature reading. The voltage measured by the PCM will be high when the intake air temperature is cold, and low when the air temperature is warm.