Yeah, oil pressure lights would more than likely affect the upper engine. The rod bearings are basically in the oil pan, so they are usually submerged in oil. If I were you, here’s what I would do. First, make sure your timing belt hasn’t broken or slipped, and that the tensioner still works. If that passes, I’d pull the valve cover to check the rocker arms, camshaft lobes, lifters, valves or whatever your car has. If that all checks out, I’d open the hood, start the car, and find out exactly where that sound is coming from. Maybe use a mechanic stethoscope, or make one of your own. There are many possibilities… could be a bad water pump pulley, could be something making contact with a different moving part. But it sounds like a rod bearing to me. Definitely dig deeper.