FixVault

System Diagram

WARNING: This page is about a different car, the 2006 Lexus GS 430 and 2006 Lexus GS 300. However, it is still accessible from the selected car via links, so may be relevant.
Fig 1: Window Defogger System Diagram
G04023093Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

Communication table 

RESULT PROCEDURE CHART

Sender
 
Receiver Signal Line
Multi-display A/C amplifier assembly (A/C ECU) Rear defogger switch signal BEAN / AVC-LAN
A/C amplifier assembly (A/C ECU) ECM Rear defogger switch signal BEAN / CAN