CRUISE CONTROL ISSUES, 2014 PRIUS V in Prius Club Posted March 6, 2018 · Report reply While in Cruise Control, Dynamic (Radar) at about 70 mph, for no apparent reason a chime will ring 4 or 5 times and the car will slow down dramatically (brakes) to about 60 mph, only to aggressively speed back up to 70. It may repeat this several times until I just hold the accelerator to hold speed. Weather, sunny and dry. Traffic, often NONE! Sporadic. it may go months without a re-occurrence.