Intake Air Temperature Sensor
What is an intake air temperature sensor?
An intake air temperature sensor can be
located in the intake air duct from the air filter box or in the intake manifold to the engine. It’s job is to report the temperature of the outside air being drawn into the engine. The intake air temperature sensor reports its findings directly to the powertrain control module or engine control module. The PCM/ECM uses the intake air temperature reading to calculate how much fuel to add to the incoming air.
Intake air temperature sensor and MAP sensor
In a speed/density system, the PCM/ECM uses the intake air temperature sensor readings in conjunction with the readings from the manifold absolute pressure sensor to estimate the DENSITY of the incoming air. The manifold absolute pressure sensor takes a reading of the barometric pressure when the driver turns the key to the ON position. Then, once the engine starts, it takes a constant reading of intake manifold vacuum. Barometric pressure minus manifold pressure while running equals manifold absolute pressure. When MAP readings are used with intake air temperature sensor readings, the computer can mathematically calculate incoming air density and air volume to calculate the proper air fuel mixture for the current engine temperature using the readings from the engine coolant temperature sensor.
Types of intake air temperature sensors
The intake air temperature sensor can be a stand-alone sensor or it can be incorporated into other sensors like the MAP or Mass Airflow Sensor (MAF).
How does an intake air temperature sensor work?
Most intake air temperature sensors are either positive temperature coefficient or negative temperature coefficient thermistors. The PCM/ECM supplies a voltage to the sensor and the sensor alters the incoming voltage by applying a varying amount of resistance based on the air temperature.
A negative temperature coefficient thermistor decreases resistance as the temperature increases, while a positive temperature coefficient thermistor increases resistance as the temperature increases.
If the PCM/ECM supplies a 5-volt input signal, it should see a return voltage as shown below
What goes wrong with the intake air temperature sensor?
Like any other sensor, the sensing element can fail, the terminals in the electrical connector can corrode and alter the readings, or the wiring harness can develop a short or open.
How to test an intake air temperature sensor?
You can test an intake air temperature sensor using a digital Ohm Meter set on the DC volts scale. Turn the IGN switch to the ON position and backprobe the return wire to see the voltage being reported to the PCM/ECM. You can also test the sensor’s resistance, but that’s not as accurate as reading the actual return voltage.
How to replace an intake air temperature sensor?
Intake air temperature sensor (IAT) sensors can be screwed into the intake manifold or simply pushed into a rubber grommet. Remove the old sensor and install the new sensor in its place.
©, 2018 Rick MuscoplatPosted on by Rick Muscoplat