Intake Air Temperature Sensor
The Intake Air Temperature (IAT) sensor is a variable temperature sensitive resistor. Sensor resistance will change based on air temperature. The higher the temperature, the lower the resistance. The Engine Management System (EMS) provides a reference voltage and monitors the voltage drop between a fixed value internal resistance and the sensor resistance. This is called a voltage divider circuit.
IAT sensor values are used by the EMS to assist with the calculation of idle speed, fuel mixture and spark advance.
Inaccurate voltages from the IAT sensor may affect pulse-width, idle quality and tail pipe emissions. Intermittent signals may cause hesitation, stumble and surging. If an IAT sensor failure accompanies an Engine Coolant Temperature (ECT) sensor failure cooling fan operation may also be affected.
Some manufacturers' incorporate the Intake Air Temperature (IAT) sensor as part of the Mass Air Flow (MAF) sensor, or air flow meter. Refer to current service information for specific applications.
The following symptoms can be caused by a faulty IAT sensor due to loose connections, bad grounds, high resistance in the circuit, or opens in the circuit.
- Extended crank time when the engine is cold
- Poor fuel economy
- Spark knock