IAC Valve Operation
WARNING: This page is about a different car, the 1997 Lexus ES 300. However, it is still accessible from the selected car via links, so may be relevant.
Remove IAC valve from throttle body. Using a 12-volt battery, connect positive lead to terminal +B of IAC valve. See Figure. Connect negative lead to terminal RSC (valve should close), then to terminal RSO (valve should open). Replace IAC valve if it does not operate as specified.