The intake air temperature sensor plays a vital role in a vehicle's exhaust system. Essentially, this sensor is what regulates the temperature of any air coming into the vehicle. A car's computer system will make adjustments based on what the air is like, as hot and cold air functions differently in a vehicle. If your sensor is working improperly, however, the computer will not get accurate readings and will make adjustments that could negatively impact the performance of your vehicle. This could also cause the "check engine" light to come on.
Thus it is important to ensure that this sensor is working correctly. Fortunately, testing your intake air temperature is rather easy, and you will need an ohmmeter to do so. Many automotive parts stores sell this useful measuring tool, with prices ranging from quite cheap for basic models to expensive for professional-grade devices. If you plan on doing a decent amount of maintenance work, you'll likely find that an ohmmeter is a handy tool to have.
The intake air temperature sensor is located within the air cleaner duct in most vehicles. This is a part of the vehicle that can get very hot after the engine is turned on, and you can severely burn yourself if you're not careful. Make sure that the engine is off and has been left to cool for a while before attempting this test.
You can remove the air temperature sensor from the housing pretty easily. Make sure the sensor is cool as well before starting the test. You'll need your trusty ohmmeter, a hair dryer and your owner's manual.
First, hold the ohmmeter up to the sensor and take a reading. Write this down or remember it. This will be your "low end" or "cool" reading. Then turn the hair dryer on and aim it at the sensor, simulating the effect of hot air coming into a vehicle. Hold the ohmmeter up to the sensor again and record that number as well.
Your owner's manual should list what the acceptable range, measured in ohms, is for an intake air temperature sensor. If your reading matches up with the range, then it's likely some other part that's malfunctioning. However, if your car is still having problems after installing the sensor, the problem may lay with the computer, which you can reset by disconnecting the negative battery charge for five minutes.