Headlights inoperable
No lamps working, what could it be?
Using the wiring diagram provided you can see there is a main fuse and relays involved. Check those first before moving on to checking the combination switch. The combination switch would be the most common failure component.
Combination Switch – 2001 Lexus RX300 …
DRL (Daytime Running Lights) Relay Testing/Inspection
Headlight wiring diagram 1 of 2 – 2001 Lexus RX300
(best viewed in Google Chrome or Firefox)
2001-lexus-rx300-headlights-headlamps-circuit-1-of-2