WARNING: This page is about a different car, the 2003 Lexus ES 300 and 2002 Lexus ES 300. However, it is still accessible from the selected car via links, so may be relevant.
Fig 1: Automatic A/C-Heater System Wiring Diagram (2000-01 ES 300 - 1 Of 2)
Fig 2: Automatic A/C-Heater System Wiring Diagram (2000-01 ES 300 - 2 Of 2)