Circuit Description

The DTC P0111 Intake Air Temperature (IAT) Sensor Performance diagnostic checks the accuracy of the IAT sensor signal. The IAT sensor is a thermistor, a variable resistor whose conductive value changes with temperature, 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 it into a temperature reading. When the outside air temperature is cold the IAT sensor resistance is high, and when the outside air temperature is warm the IAT sensor resistance is low. Therefore, when the air temperature is cold the PCM will receive a high voltage input, and when the air temperature is warm the PCM will receive a low voltage input.