Circuit Description
WARNING: This page is about a different car, the 2003 Lexus IS 300 and 2002 Lexus IS 300. However, it is still accessible from the selected car via links, so may be relevant.
When the ignition switch is turned to the ACC position, battery positive voltage is applied to the terminal No. 4 (ACC) of the body ECU and when the ignition switch is turned to the ON position, battery positive voltage is applied to terminal No. 3 (IG) of the body ECU. For circuit diagram, see Fig 1.