Taillight Disconnection Warning
WARNING: This page is about a different car, the 2008 Lexus SC 430. However, it is still accessible from the selected car via links, so may be relevant.
If any taillight wiring is faulty when the ignition SW is turned to the ON position with the light control SW set at TAIL or HEAD, the luggage room J/B ECU detects a voltage difference and is activated to turn on the rear lights warning light in the combination meter to warn the driver.