The National Highway Traffic Safety Administration (NHTSA) flagged concerns about Tesla Inc‘s TSLA projection of its Full Self Driving (FSD) driver assistance software on social media platform X in a letter to the EV giant.

What Happened: Tesla’s FSD technology is a driver assistance technology that requires active driver supervision. While vehicle owner manuals and YouTube videos clarify that the technology does not make the vehicle autonomous, Tesla’s X account has reported or endorsed postings that “exhibit disengaged driver behavior,” the auto safety regulator wrote in a letter to Tesla dated May 14. The letter was made public on Friday.

“We believe that Tesla’s postings conflict with its stated messaging that the driver is to maintain continued control over the dynamic driving task. We similarly observe that these postings may encourage viewers to see FSD-Supervised as a Chauffer or “Robotaxi” rather than a partial automation / driver assist system that requires persistent attention and intermittent intervention by the driver,” the regulator said while requesting the EV giant to revisit its communications. The regulator also noted that social media posts communicate better with the public than vehicle owners’ manuals.

Why It Matters: In October, NHTSA opened an investigation into nearly 2.4 million Tesla vehicles on the heels of reports of four crashes where FSD was engaged.

The regulator said that it has identified four crash reports in which a Tesla experienced a crash after entering an area of “reduced roadway visibility” with FSD engaged. The reduced visibility, the regulator said, was caused by sun glare, fog, or airborne dust. In one of the crashes, the vehicle struck and killed a pedestrian, the regulator added.

The regulator has now given Tesla time till Dec. 18 to answer its questions as part of the investigation and to furbish details of crashes that the company is aware of.

Tesla issued a recall for over 2 million vehicles in the U.S. in December equipped with all versions of Autosteer (part of Tesla’s suite of advanced driver assistance features called autopilot) after deeming the feature’s controls to be insufficient to prevent misuse. The company said it would enhance its safeguards but NHTSA opened a probe in April to gauge the adequacy of the fix provided by the carmaker.

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