Fuel Pump Speed Control
WARNING: This page is about a different car, the 1997 Lexus SC 300. However, it is still accessible from the selected car via links, so may be relevant.
Under normal driving conditions (low engine speed or low engine load), the fuel pump ECU applies 9 volts to the fuel pump. When the engine requires more fuel, the fuel pump ECU applies 12 volts to the fuel pump.