Modern cars contain a large number of automation and control equipment. One of these devices is an intake air temperature sensor (DTVV), which monitors the state of incoming air masses from the environment. What this device is, and what malfunctions the car owner may encounter, we will consider in this article.
Purpose and location
The temperature sensor is designed to control the temperature of the air supplied from the environment. Depending on the air temperature, the state of the air-fuel mixture and its flash point in the cylinder change. In the event of excessive cooling or heating of the air outside, the driving mode of the car may differ significantly. The sensor reacts to temperature changes and sends a signal to the control unit to change the current operating parameters.
Therefore, the direct function of the intake air temperature sensor is to measure the current parameters. Indirectly, it is designed to increase or decrease the volume of the supplied fuel mixture in accordance with external factors.
Such a temperature sensor is installed in the vehicle air supply system. As a rule, it is located in the immediate vicinity of the air filter or on its housing, in some models it can be located in the intake manifold.
The positioning method involves directing the sensing element into an air stream. Therefore, the installation site should provide for a clear fixation, since when the sensor is displaced in the mounting hole, you will receive unclear readings.
Device and principle of operation
For a better understanding of possible malfunctions and malfunctions, it is necessary to understand its structure and principle of operation.
The temperature sensor for monitoring the intake air consists of:
- Pin connector - to connect the temperature sensor to the internal electrical circuit;
- Housings - designed to protect against mechanical damage and external factors on electronic components;
- Sensing element - to fix the temperature of the incoming air, a thermistor is used, which can be located both in an open cap and in a sealed flask.
- Landing choke - an element equipped with a thread for screwing in at the air temperature control point.
Note that there is an O-ring between the two for a snug fit of the sensor to the mounting surface. Otherwise, air will leak from the system.
The principle of operation of the intake air temperature sensor is based on the readings of a thermistor with a negative temperature coefficient. In accordance with clause 23 of GOST 21414-75, this is such a nonlinear element, the ohmic resistance of which decreases as the thermistor itself heats up. The position of the sensor is selected in such a way that the sensor interacts directly with the moving air, otherwise the work proceeds as follows:
As you can see in the figure above, when the flow of air sucked into the system moves, it directly affects the sensor, flowing around the thermistor. At the beginning of starting the engine, the air in the pipe will be cold and, when interacting with the thermistor, its resistance will be within a few kΩ.
If the air temperature in the system rises, the resistance of the sensor will begin to decrease, the voltage drop will decrease and the current will increase. As soon as the parameter reaches the set limit, sufficient current will flow in the control circuit to command the control unit.
In the case of cold air passing, a weighting effect arises that requires injection of more fuel into the cylinder to maintain normal operation. When the temperature rises, the sensor will respond with a proportional decrease in resistance, and the control unit will give a command to narrow the injectors and reduce the volume of injected fuel.
Thus, the motor operation is adjusted, depending on the temperature of the supplied air. However, the system can malfunction, significantly affecting the operation of the vehicle.