Where is the oil pump located on a 98 cadillac catera I have a drop in oil pressure when I am going 15 to 20 mph It drops so low the light comes on could this be my problem or is it something else?

If your oil pressure light comes on when the temperature shows high and pressure shows low, may be partly due to too thin oil.

If you are using 5W-30 change to 10W-40 during warm weather, the light will not come on with the high oil temperature.