Many hard start issues and other fuel related issues can be tied to the factory rail pressure sensor. This sensor monitors the high pressure fuel located in the fuel rail and tells the computer what the pressure is. Then, the computer is able to make adjustments to the injection pump's pressure (as well as many other parameters) to compensate for a smooth running engine. However, if that signal is not being picked up and sent properly, many problems will persist. This is a direct OE replacement sensor for the factory unit.