Circuit Description
WARNING: This page is about a different car, the 2002 Lexus RX 300 and 2002 Lexus ES 300. However, it is still accessible from the selected car via links, so may be relevant.
When ignition switch is turned on, 9-14 volts is applied to the terminal IGSW at ECM main relay control circuit, sending a signal to terminal MREL at ECM, which then switches EFI main relay on. When ignition is turned off, ECM will keep EFI main relay on for 2 seconds or less in order to reset Idle Air Control (IAC) valve.