The Intake Air Temperature (IAT) sensor resistance changes in response to the intake air temperature. The sensor resistance decreases as the surrounding air temperature increases. This provides a signal to the PCM, indicating the temperature of the incoming air charge.
The MAF sensor uses a hot wire sensing element to measure the amount of air entering the engine. Air passing over the hot wire causes it to cool. This hot wire is maintained at 200°C (392°F) above the ambient temperature as measured by a constant cold wire. The current required to maintain the temperature of the hot wire is proportional to the mass air flow. The MAF sensor then outputs an analog voltage signal to the PCM proportional to the intake air mass. The PCM calculates the required fuel injector pulse width in order to provide the desired air/fuel ratio. This input is also used in determining transmission Electronic Pressure Control (EPC), shift and torque converter clutch scheduling.
The MAF sensor is located between the air cleaner and the throttle body or inside the air cleaner assembly. Most MAF sensors have integrated bypass technology with an integrated Intake Air Temperature (IAT) sensor. The hot wire electronic sensing element must be replaced as an assembly. Replacing only the element may change the air flow calibration.
Removal & Installation
- Disconnect the battery ground cable.
- Disconnect the Intake Air Temperature/Mass Air Flow (IAT/MAF) sensor electrical connector.
- Remove the IAT/MAF sensor retaining screws. To install, tighten to 53 inch lbs. (6 Nm).
- Remove the IAT/MAF sensor.
- To install, reverse the removal procedure.
- Turn the ignition switch OFF before testing the sensor.
- Disengage the wiring harness connector from the IAT sensor.
Using a Digital Volt-Ohmmeter (DVOM), measure the resistance between the two sensor terminals.
- Compare the resistance reading with the accompanying chart. If the reading for a given temperature is approximately that shown in the table, the IAT sensor is okay.
- Attach the wiring harness connector to the sensor.
IAT Sensor Pin Testing
This pinpoint test is intended to diagnose the following: