"L" Position
WARNING: This page is about a different car, the 2002 Lexus ES 300. However, it is still accessible from the selected car via links, so may be relevant.
While driving, place selector lever to "L" position and ensure there is no upshift to 2nd gear. While driving in "L" position, release accelerator pedal. If there is no engine braking effect, 1st/reverse brake is defective. Check for abnormal noise during acceleration and deceleration.