I have a 2001 dodge and when I am driving the oil pressure gauge will drop and check engine light comes on and the truck starts knocking. The only way to fix it is to turn the truck off and on

If the engine has not recieved regular oil changes it is possible the oil pan is full of sludge in the bottom. When the gunk is sucked up you loose oil pressure, when you shut it off it falls off and oil pressure will return again. You may be able to fix this by changing the oil except put 2 quarts of transmission fluid in with 3 quarts of oil. Change the filter and run it as long as you have oil pressure (stopping when it drops) for about a hour or so of total run time. Don't drive it just let it run it at idle. Drain the oil again and replace the filter again. refill it with fresh oil. If this does not fix the problem you will have to drop the pan and inspect/replace the oil pump.