This is the front left (driver side) oxygen sensor for the 5.4L engine. Most modern cars have 3 to 4 separate oxygen sensors, defined by their location (front, rear, left, right, pre-cat, post-cat, etc.). In addition to the year, make, and model of your vehicle, you need to know the engine size and the exact location of the oxygen sensor which needs replacing. If you are unsure, we would suggest that a professional repair shop perform the diagnosis.