The National Highway Traffic Safety Administration has opened a formal investigation of Tesla over reports of "phantom braking" in 2021-22 Model 3 and Model Y electric vehicles. Some 354 complaints over the last nine months have alleged that these EVs can apply their brakes unexpectedly and without reason when Autopilot is engaged. (Autopilot is not self-driving hardware but Tesla's name for its suite of Advanced Driver Assist Features.)

The probe's filing paperwork, which covers 416,000 examples of the electric sedan and crossover SUV, states: 

"The complaints allege that while utilizing the ADAS features including adaptive cruise control, the vehicle unexpectedly applies its brakes while driving at highway speeds. Complainants report that the rapid deceleration can occur without warning, at random, and often repeatedly in a single drive cycle."

Older Model 3 and Model Y EVs are not part of the investigation, but owners have reported similar incidents on both social media and NHTSA's own website.

Roadshow's Editor-in-Chief Tim Stevens has reported experiencing phantom braking on our company's long-term Tesla Model Y many times, even capturing the phenomenon on video. The issue persists despite multiple over-the-air, or OTA, updates to the car's firmware. Other CNET staffers who own Tesla vehicles have also reported the Autopilot braking episodes.

As part of its investigation, the NHTSA will gather evidence and data from owners and Tesla, giving the automaker the opportunity to discuss the matter. The federal agency will then decide to either close the investigation or escalate matters, which could trigger a request for a recall. The NHTSA has the authority to initiate a recall against an automaker's wishes (read: nonvoluntarily), but such scenarios are extremely rare.

Tesla has been under increasing federal scrutiny as of late, including investigations and recalls centered on everything from seatbelt chimes to its Boombox feature and ADAS programming that deliberately and illegally violated stop signs.

Tesla did not immediately respond to Roadshow's request for comment on this story. Unlike other automakers, the company no longer operates a PR department to field media requests.