Circuit Description
WARNING: This page is about a different car, the 2003 Lexus IS 300. However, it is still accessible from the selected car via links, so may be relevant.
Fuel pump speed is controlled at 2 steps (high speed, low speed) according to condition of engine (starting, light load, heavy load). When engine starts, ECM turns fuel pump relay OFF to operate fuel pump at high speed. After engine has started, during idling or when load is light, ECM turns fuel pump relay ON to operate fuel pump at low speed. When intake air increases (heavy load), ECM turns fuel pump relay OFF to operate fuel pump at high speed. There are 2 fuel pumps. The ECM switches from main to sub or sub to main every time ignition switch is turned on and off.
DTC is recorded when open or short is detected in fuel pump relay circuit for .5 second or more during cranking. Possible causes are:
- Open or short in fuel pump relay circuit.
- Faulty fuel pump relay.
- Faulty ECM.