Circuit Description
WARNING: This page is about a different car, the 2002 Toyota Prius. However, it is still accessible from the selected car via links, so may be relevant.
Battery positive voltage is supplied to terminal AM of the Battery ECU even when the ignition switch is OFF to read the DTC memory and freeze frame data adaptive control value memory, etc.
NOTE:
If DTC P1600 appears, the Battery ECU does not store any other DTC.