Hi Julie. That could be the oil pump in the engine and could be a bad situation if it goes out. Can you take it back to whoever put the sending unit in it and have them triple check that they clicked it into the harness? I would check it for codes too. Any auto parts store can do that for free. If the oil pump was to go out - it will start making noise and then generally can ruin an otherwise good engine. Sometimes it can be the pick up screen on the pump too. They will get clogged with crud and not let it pick up oil.