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.

What is the MAT Sensor?


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.

How does the MAT Sensor work?

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.

What is the Manifold Air Temperature Sensor used for?

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.

MAT Sensor Types

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.

Common MAT sensor failures and solutions

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.

Symptoms of common MAT sensor failures

MAT sensor malfunctions can produce the following symptoms:

Low power when accelerating the car

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.

Difficulty at cold start.

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.

Decreased fuel efficiency

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.

Solutions to MAT sensor failures

  • It is important to have the wiring harness and the EHV sensor checked every 45,000 km.
  • Make sure the wiring is not damaged, either open or shorted. If it is, then it should be replaced.
  • That the harness is not rusted, sulfated or broken. If it meets any of these conditions it should be replaced.
  • Check that there are no deposits of impurities on the tip of the device causing a poor signal. Clean or replace the sensor in this case.

OBD2 codes related to the MAT sensor

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:

  • Code # 23: Estimates that the signal is too low.
  • Code # 25: Indicates that the signal is too high.

How to test the Manifold Air Temperature Sensor?

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.

How to clean the MAT sensor?

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:

  • Carefully remove the sensor from its location.
  • The sensor may have a latch on it, remove it carefully.
  • Pull the sensor out once it is disconnected.
  • Clean with a fast-drying, non-aggressive cleaner. It can be a Contact Cleaner or contact cleaner.
  • After cleaning you should put the MAT sensor back in place, applying some pressure.

Where is the Manifold Air Temperature Sensor located?

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.


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