Circuit Description
WARNING: This page is about a different car, the 2002 Lexus SC 430. However, it is still accessible from the selected car via links, so may be relevant.
A 2-speed fuel pump is used to control fuel pressure. During engine cranking, ECM turns on control circuit of fuel pump relay in order to apply battery voltage to fuel pump and increase fuel pressure. Once engine starts, or while running under light load conditions, ECM opens fuel pump relay control circuit. Fuel pump voltage is then fed through fuel pump resistor, which lowers fuel pump voltage and reduces fuel pressure. Under heavy load conditions, ECM turns fuel pump relay back on to increase fuel pressure.