Open Door Warning Light
WARNING: This page is about a different car, the 2003 Lexus IS 300 and 2002 Lexus IS 300. However, it is still accessible from the selected car via links, so may be relevant.
Disconnect the connector from the door courtesy switch and ground terminal No. 1 on the wiring harness side, and check that the warning light lights up. If the warning light does not light up, inspect the bulb or wiring harness.