What Causes this?

My wife called me while I was on the way home from Florida and told me my Tahoe was broke down. I have checked everything. The fuel pump is not getting power and I'm not getting fire from the plugs. I have been told there are two sensors that will cause both to lose power. I replaced one and I think they told me the other is on the distributer shaft. Does anyone know what it is called? Has anyone had this happen before?