NHTSA Complaint #11449977 — 2021 TESLA MODEL Y

On a recent trip to Minnesota when adaptive cruise control was engaged there were several ( >10) episodes when the car would suddenly decelerate for no apparent reason. On a two lane highway it might occur if a large vehicle such as a truck was oncoming in the opposite lane. On the interstate, the common scenario was traveling in the right lane going up a slight upgrade with a car passing in the left lane. Often the sudden speed reduction was 25 mph or more. On occasion even on a flat section the car might suddenly brake for no apparent reason. On one occasion this happened in the afternoon going west with the sun glinting off some shiny asphalt crack filling. No accident occurred, but if a car were following closely, sudden braking could cause a crash. Because of this erratic behavior I don't use adaptive cruise control except for short distances. This is a known Tesla problem, but it seems the company is more interested in enhancing games to be played while charging rather than attend to a major flaw.