Fuel Pump Control System

Fig. 73:

CIRCUIT OPERATION
The ECU controls the voltage supplied to the fuel pump through a relay and through a separate circuit. The relay is only used in the "Back-Up Mode". Refer to BACK-UP SYSTEM for further description.
The ECU transmits a pulsing voltage signal (Hz). The higher the frequency (Hz) or "Duty Cycle" (100%) the more voltage that is applied to the pump. The ECU lowers the duty cycle (amount of time on vs. amount of time off) to lower passenger compartment noise levels and power consumption. The ECU supplies full battery voltage when starting, for a few seconds after the ignition is turned on and during hot and cold operating conditions.