Headlights and fog-lights are inoperable. The headlights and fog-lights are controlled by the combination switch. This switch signals the the Body ECU to activate the headlamp relay. The headlamp relay receives its battery power from a 50amp "Main Fuse" that is hot at all times.…
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 … Details
DRL (Daytime Running Lights) Relay Testing/Inspection
Headlight wiring diagram 1 of 2 – 2001 Lexus RX300
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