When DTC code P0088 OBD2 is set it is because the Powertrain Control Module (PCM) has detected an excessive level of input voltage from the Fuel Rail Pressure Sensor (FRP) or a very high pressure on the fuel rail.
The FRP sensor has a reference signal of 5 volts. In addition, it has a ground signal. If the fuel pressure increases, the resistance of the sensor decreases. When fuel pressure rises and sensor resistance drops, the signal voltage from the sensor to the PCM must increase accordingly, with 4.5 being the maximum voltage.
To achieve efficient fuel consumption, the FRP sensor adjusts the voltage of the fuel pump, seeking to achieve the necessary amount of pressure on the fuel rail. If the fuel rail pressure is higher than the amount programmed in the PCM, diagnostic code P0088 is stored.