Circuit/System Description

The intake air temperature (IAT) sensor is integrated with the mass air flow (MAF) sensor. The IAT sensor is a variable resistor that measures the temperature of the air when it first enters the induction system. The engine control module (ECM) supplies 5 volts to the IAT signal circuit and a ground for the shared MAF/IAT low reference circuit.

The purpose of this diagnostic is to analyze the performance of the IAT sensor by comparing the response and the range of the sensor signal to two distinct models under various operating conditions.

• The first model verifies that the sensor is not stuck in range.
• The second model verifies that the sensor is within an acceptable operating range of the calculated IAT.

  Both models use various parts of the information derived from the following inputs:

  • Ambient air temperature (AAT)
  • Barometric (BARO) pressure
  • Distance driven
  • Engine coolant temperature (ECT)
  • Engine OFF time
  • Engine run time
  • IAT
  • MAF
  • Throttle position (TP)
  • Vehicle speed (VS)