Explains the Fuel Rail Pressure OBD-2 Scanner Parameter. The fuel rail pressure sensor is used by the ECM to control the fuel pump motor speed. In an effort to protect the fuel lump electric motor, a fuel rail pressure sensor and software modules are employed. At slower or cruising speeds there's little need for large fuel consumption, so the fuel pump voltage and speed are reduced. The end result is a FP that lasts longer. See it here; how it works and how to test it. (note: We allow all schools and training institutions to use our software free of charge, so long as it is not sold to others. You're encouraged to download our free automotive simulation software for more information.