1. Open the hood of your car.
2. Locate the air filter housing, which is usually a black plastic box located on the top of the engine.
3. Disconnect the air intake hose connected to the air filter housing by loosening the hose clamp.
4. Look inside the intake hose or duct where it was connected to the housing.
5. You should see the IAT sensor, which is usually a small, cylindrical sensor with wires connected to it. It may be held in place by a screw or snap-fit into the air duct.
Note: The exact location of the IAT sensor on your vehicle may vary slightly from this general description depending on the specific model and year of your Nissan Altima. If you have difficulty finding it, consult your vehicle's repair manual or seek assistance from a professional mechanic.