You didn't say which engine you have so you'll just have to look on the intake plenum or fresh air tube. That sensor practically never fails unless it's handled very roughly. By far the most common cause of that fault code is the sensor was unplugged. It will have a two-wire plug
Fuel doesn't vaporize easily in colder weather, and the air is more dense. Both of those conditions require more fuel to enter the engine. That's why the Engine Computer needs to know air temperature. When it doesn't know the temperature, it's going to command plenty of fuel to insure the engine runs right, whatever the temperature is. That means you'll be using more fuel than necessary. The computer will get an idea of air temperature from the coolant temperature sensor when the engine is first started, but the fault code will prevent some other self-tests from running because the computer needs the IAT to make comparisons. That is more likely to become a problem when people ignore the Check Engine light for weeks or months. That gives a totally new problem time to occur, but it may not be detected because of those tests that fail to run. Then, when the first problem is finally repaired, the customer picks up the vehicle, then the Check Engine light turns right back on again. Of course they assume the car wasn't repaired properly, but in reality the mechanic had no way of knowing there was another problem.
The Check Engine light should turn off once the sensor is reconnected, and the ignition switch is turned off and back on. Normally the fault codes will erase automatically after a certain number of engine starts, but if it doesn't, you may need a scanner or code reader to erase it.
Saturday, November 30th, 2013 AT 9:01 PM