In vehicles that have the fuel supply without return, the fuel pump has a pulse width modulation allowing in this way to vary the speed of delivery of fuel to the rail. In this way the fuel pump does not need to work constantly, in addition to regulating the fuel pressure returning it to the tank.
TheFRP sensor (Fuel Rail Pressure) is the one that monitors the fuel pressure in the rail. Determine the proper pressure of this, in addition to varying the speed of the fuel pump according to the pressure.
If the PCM (Powertrain Control Module) detects that the fuel pressure is below the specifications for the supply ordered by the fuel pump, the DTC codeP0087 OBD2 is established.