The electric car manufacturer Tesla is once again facing investigations into its "Autopilot" driver assistance system.
The American traffic safety agency NHTSA has launched a preliminary investigation after customers complained about unwanted activation of the brakes in their vehicles.
This is also described as "phantom braking", the authority said.
Roland Lindner
Business correspondent in New York.
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Overall, there have been 354 such complaints in the past nine months.
Tesla drivers reported that their brakes engaged unexpectedly at higher speeds while the autopilot system was engaged.
This led to a "rapid slowdown" of the vehicles and happened without warning, randomly and often several times during a trip.
According to the authority, the investigation relates to 416,000 vehicles from the 2021 and 2022 model years.
Lots of investigations into autopilot system
Tesla has recently been the subject of repeated investigations by the safety agency and has also been forced to issue a number of recalls.
It was only recently announced that the company had removed a feature in a recall that previously allowed its cars not to stop completely at a stop sign, but to drive on slowly.
There are a particularly large number of investigations into the autopilot system.
It has been linked to a number of accidents in recent years.
NHTSA is currently investigating 30 accidents that resulted in a total of 10 fatalities.
Separately, there are also investigations into almost a dozen accidents in which Tesla cars crashed into police or fire brigade emergency vehicles despite the driver assistant being switched on.
Tesla and CEO Elon Musk have often defended the technology, saying it makes traffic safer.