Manifold Air Temperature (Mat) Sensor

The MAT sensor is a thermistor (temperature sensitive resistor) mounted in the intake manifold. Low intake air temperature produces high internal sensor resistance, while high temperature causes low internal sensor resistance. See MAT SENSOR TEMPERATURE TO RESISTANCE VALUES table in CODE 23 or 25 chart. The ECM supplies and monitors a 5-volt signal to sensor through a resistor in ECM. By monitoring this voltage, ECM determines manifold air temperature. After a vehicle has set overnight, MAT and CTS signals (resistance and temperature) should be close to same reading. Failure in MAT sensor circuit should set either a Code 23 or 25.