Where is the oil pressure sending unit located on a 2001 ford explorer sport trac?

The oil pressure sending unit on a 2001 Ford Explorer Sport Trac is located on the driver's side (left side) of the engine block, near the oil filter. It's a relatively small unit with a single wire connected to it. You'll likely need to get under the vehicle to see it clearly. Be aware that the engine is hot after running, so allow it to cool down before working on it.