* Upstream O2 Sensor: This is typically located in the exhaust manifold or very close to it. Finding a diagram specific to your engine size (4.5L or 4.9L) in a repair manual or online will be most helpful for precise location.
* Downstream O2 Sensor: This is generally located in the exhaust pipe, after the catalytic converter. Again, a diagram is crucial for pinpoint accuracy.
To find the exact location:
1. Consult a repair manual: A Haynes or Chilton repair manual for your specific year and engine size will have diagrams showing the exact location of the oxygen sensors. This is the most reliable method.
2. Use an online parts diagram: Many online auto parts stores (like AutoZone, Advance Auto Parts, etc.) allow you to select your vehicle's year, make, model, and engine, and then view diagrams showing parts locations, including oxygen sensors.
3. Visual inspection (with caution): The exhaust manifold and exhaust pipe are very hot after the engine has been running. Allow the engine to cool completely before attempting any visual inspection. Even then, wear appropriate safety gear, such as gloves. Look for a threaded sensor, typically with a wire harness connected to it, located in the exhaust system.
Without knowing your exact engine size, I cannot give you a more precise location. Using one of the methods above will be essential to locating your oxygen sensor(s).
