Coast Control
WARNING: This page is about a different car, the 2002 Lexus LX 470. However, it is still accessible from the selected car via links, so may be relevant.
When the SET/COAST switch is kept turned on during cruise control driving, the engine control module (ECM) controls the throttle valve to decelerate the vehicle speed. Every time the SET/COAST switch is turned on instantaneously, the vehicle speed is decelerated approximately 0.93 mph (1.5 km/h).