Fuel Pump Electronic Control Unit (ECU) - (GS300 & GS400)
Fuel pump operating speed is controlled by operating condition of the engine such as: starting, idling, light load or heavy load. Engine Control Module (ECM) delivers an input signal from FPC terminal on ECM to FPC terminal on fuel pump ECU in accordance with engine operating condition. Fuel pump ECU uses this input signal to determine how much voltage should be delivered to fuel pump for varying fuel pump operating speed. When engine starts or is under heavy load with engine at high speed, ECM delivers about 3.8-volt input signal to fuel pump ECU. Fuel pump ECU then provides battery voltage to fuel pump so fuel pump operates at high speed. When engine is under heavy load with engine at low speed, ECM delivers about 2.5-volt input signal to fuel pump ECU. Fuel pump ECU then provides about 10 volts to fuel pump so fuel pump operates at medium speed. When engine is idling or under light load, ECM delivers about 1.3-volt input signal to fuel pump ECU. Fuel pump ECU then provides about 8.5 volts to the fuel pump so fuel pump operates at low speed. Fuel pump ECU is located behind inner trim panel at driver's side rear corner of the trunk. See Fig 1.