Fuel Pump & Fuel Pump Primary Circuit (GX470)

WARNING: This page does not describe the selected car, but rather 9 other vehicles, including the 2003 Lexus SC 430, 2003 Lexus RX 300, 2003 Lexus LX 470, 2003 Lexus LS 430, and 2003 Lexus IS 300. However, it is still accessible from the selected car via links, so may be relevant.

Fuel pump operating speed (Low or High) is controlled by operating condition of engine such as starting, light load or heavy load. When starter relay signal and crankshaft position sensor signal are input to ECM, circuit opening relay is turned on, current flows to coil of circuit opening relay, relay switches on, power is supplied to fuel pump, and fuel pump operates. While crankshaft position sensor signal is generated (engine running), ECM keeps current opening relay on and fuel pump also keeps operating.

When engine starts, Tr2 in ECM is off so fuel pump relay closes and battery positive voltage is applied directly to fuel pump. Fuel pump operates at high speed.

When engine idles or during light loads, Tr2 goes on and power is supplied to fuel pump via the fuel pump resistor. Fuel pump operates at low speed.