The IAT sensor threads into the intake manifold, where it measures the temperature of the intake air as it enters the engine. The sensor is a Negative Temperature Coefficient (NTC) thermistor-type sensor (resistance varies inversely with temperature). This means at high temperatures, resistance decreases and so the voltage will be low. At cold temperatures, the resistance is high and so the voltage will also be high. This allows the sensor to provide an analog voltage signal to the PCM. The PCM uses this signal to compensate for changes in air density due to temperature.
- Visually check the connector, making sure it is attached properly and all of the terminals are straight, tight and free of corrosion.
- With the engine OFF, turn the ignition key to the ON position.
- Do not allow more than 5 minutes delay between the next 2 steps.
- Using a DRB, or equivalent scan tool, read the information on the Intake Air Temperature (IAT) sensor and record the reading.
- Turn the ignition switch OFF.
- Remove the IAT sensor.
- Using a temperature probe, quickly measure intake temperature inside the sensor opening.
- Replace the IAT sensor if the scan tool reading is NOT within 10 of the probe reading.
- Using a DRB, or equivalent scan tool, read the IAT sensor voltage.
- If the voltage reading measures outside of the 0.5-4.5 volt range, disengage the IAT sensor connector.
- Using the scan tool, read the IAT sensor voltage.
- If the voltage reading measures greater than 4 volts, replace the IAT sensor.
- Connect a jumper wire between the IAT signal and sensor ground circuits, then, along with the scan tool, read the sensor voltage.
- If the voltage reading measures less than 1 volt, replace the IAT sensor.