Air Temperature Sensor ( Ambient / Intake ): Description and Operation

Mass Air Flow (MAF) / Manifold Air Temperature (MAT) Sensor:

PURPOSE
The Manifold Air Temperature (MAT) sensor (part of Mass Air Flow (MAF) sensor) is a thermistor (a resistor which changes value based on the temperature). This changing resistance supplies the Electronic Control Module (ECM) with the temperature of the air entering the engine.

OPERATION
The ECM supplies a 5 volt signal to the sensor through a resistor in the ECM and measures the voltage. The voltage will be high when the intake air is cold and low when the air is hot. By measuring the voltage, the ECM knows the manifold air temperature. The MAT sensor is also used to control spark timing and delays Exhaust Gas Recirculation (EGR) when intake air is cold. A failure in the MAT sensor circuit should set either a Code 23 or Code 25.Once a trouble code is set, the ECM will use a default valve for MAT.

NOTICE: Vehicles with Speed Density Update do not use Mass Air Flow (MAF) readings. Their Engine Control Modules (ECM)s have been modified.