Rear Window Defogger System does not Operate: Description
WARNING: This page is about a different car, the 2007 Lexus SC 430. However, it is still accessible from the selected car via links, so may be relevant.
When the A/C amplifier defogger switch is pressed, a signal is sent via the BEAN line to the luggage room junction block ECU. Then the luggage room junction block ECU operates the rear window defogger.