Brake Fluid Level Switch
WARNING: This page is about a different car, the 2002 Toyota Avalon. However, it is still accessible from the selected car via links, so may be relevant.
Turn ignition off. Remove cap and strainer from brake fluid reservoir. Disconnect brake fluid level switch connector. Check for continuity between brake fluid level switch terminals. With reservoir full (float up), continuity should not exist. With reservoir empty (float down), continuity should exist. If continuity is not as specified, replace brake fluid level switch.