Where is the oil pressure sending unit on a 1999 Toyota Avalon?

The oil pressure sending unit on a 1999 Toyota Avalon 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 might need to look closely and possibly use a flashlight to locate it. Be aware that the area around the oil filter and oil pressure sending unit is oily and can be hot if the engine has been running recently.