POST UPDATED IN May, 2023
Manifold Air Temperature Sensor
The Manifold Air Temperature Sensor is responsible for measuring the air temperature and then sending this data to the vehicle’s computer, which will balance the amount of incoming air. Its operation is similar to that of the IAT sensor, except that it is located in a different place.
This sensor is a thermistor that senses the air entering the engine to detect its temperature. This temperature manages to vary the resistance of the thermistor so that it manages to generate a signal that is sent to the ECU. It consists of two wires, the ground wire, and the voltage signal wire. Its hermetic capsule achieves the tightness to keep the absolute pressure almost at zero. With a chip or integrated process, the signal is sent to the vehicle’s computer.
The density of the air entering the combustion chamber can vary, taking into account its temperature. This variation is captured by the MAT Sensor, which will send the signal to the ECU to adjust the fuel injection.
As the amount and temperature of the intake air vary, the oxygen concentration also varies, so the fuel injection needs to be adjusted to balance the mixture. If the air temperature is higher, the resistance will be lower. Under that analysis, the ECU regulates the changes, either by cold start or also by other conditions such as altitude.
This thermistor manages to convert a temperature signal into an electrical signal. The objective is for the vehicle’s computer to have all the references involved in the combustion process, including the intake air temperature.
The manifold air temperature sensor is a negative coefficient type. That is, proportional to the air temperature. The unit of measurement of the thermistor is given in ohms. Actually, manufacturers have not introduced major changes in this sensor, so a classification by type will have to be made.
The MAT sensor can sometimes fail for a variety of reasons and exhibit open circuits, short circuits, or internal electrical damage. The ECU will evaluate the ranges of the readings delivered by the piezoelectric device. When the values are outside the preset minimum and maximum, then it determines that the sensor is faulty. The Check Engine light will illuminate on the dashboard indicating an engine failure.
Under these conditions, the ECU enters an alternate program to maintain engine operation. It does this until the problem is resolved, either by replacing the damaged MAT sensor or the deteriorated wiring. Wires may be shorted or disconnected as a result of a trapped or accidentally severed connection with some tool, movement, or extreme engine temperature.
MAT sensor malfunctions can produce the following symptoms:
This is since the damaged or defective sensor does not send the proper signal to the ECU, resulting in fuel mixture calculations that are not the most accurate and, of course, a failure occurs.
If the MAT sensor fails, the signal sent to the ECU is poor. The system cannot deliver the extra fuel required to start the engine cold.
As mentioned above, all of the problems caused by the MAT sensor failure result in inaccurate calculations coming from the ECU. Inaccurate calculations cause fuel deficiency deduction.
For this temperature sensor, the code nomenclature varies a little. Following the ODBII diagnostic process we will find the following codes with the respective meaning that we point out:
As with other sensors, the tool to use is a multimeter. You can also use a hairdryer or a heat gun. Remember that this sensor is a thermistor, so you will be able to generate a reaction if you apply heat to the end.
If the ohms measurement does not change as the temperature increases, the sensor is damaged and should be replaced. Note that as the temperature increases, the resistance should decrease.
If the measurement is made at room temperature, the signal should measure 2-kilo ohms.
Sensors are delicate electrical elements that must be handled with extreme care. Cleaning the MAT sensor may result in irreparable damage if not done with caution. In addition, cleaning is not a sure guarantee that the problem will be solved. However, here are some things to keep in mind when cleaning the sensor:
The location of the sensor is between the air filter and the intake manifold. Typically, there is a duct or hose that allows this sensor to be attached. There may be some variation in location by manufacturer, therefore, you can find out the exact location of the MAT Sensor by acquiring the electrical diagrams of the car.