Low oil pressure is a common occurrence. No need to think about a rebuild yet. Your problem is either in the oil-sending unit or the sensor for the sending unit. The differentiation is quite simple. If the truck starts up fine, it’s the sensor that needs to be replaced. It’s also a good idea to make sure that the electrical connection to the sensor is clean and in good condition. If it’s hard or not starting, you’ll need to replace the oil-sending unit.