Where is the oil pressure sending unit on a 1999 I6 Jeep Grand Cherokee?

The oil pressure sending unit on a 1999 Jeep Grand Cherokee with an inline-6 (I6) engine is located on the passenger side of the engine block, near the front. 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 it might be somewhat difficult to access due to other components in that area.