The National Highway Traffic Safety Administration opened its second investigation of possible defects related to Tesla Inc.’s Autopilot, subjecting more scrutiny to the carmaker’s driver assistance technology.
The agency said Thursday it was launching a preliminary evaluation of unexpected braking by Tesla Model 3 sedans and Model Y sport utility vehicles. NHTSA estimates that the investigation covers about 416,000 cars and said it has received 354 complaints related to the issue in the past nine months.
The regulator has initiated three probes into possible Tesla defects since August, when it began investigating how Autopilot handles crash scenes after the system was involved in a dozen collisions with first responders and other vehicles. In December, NHTSA opened an evaluation of Tesla software that allows car occupants to play video games on dashboard touch screens. The carmaker told the agency it would work on a software update to lock the feature when vehicles are in motion.
The Autopilot probes could pose a risk to Tesla’s commercialization of automated-vehicle technology. In the weeks leading up to the company becoming the first carmaker with a $1-trillion market value, Chief Executive Elon Musk tweeted that investors were giving Tesla “significant credit for achieving self-driving.”
Tesla shares fell 4.6% to $880.73 at 11:04 a.m. Eastern. The stock extended its decline after the carmaker sank toward the bottom of Consumer Reports’ newest annual auto brand rankings.
Tesla has marketed systems dubbed Autopilot and Full Self-Driving that still require attentive human drivers. The company has drawn criticism from the likes of the National Transportation Safety Board, former NHTSA leaders and members of Congress over issues including how it’s branded the systems and whether it does enough to safeguard against inattentiveness and misuse.
NHTSA opened its latest probe two weeks after announcing it was reviewing complaints that Teslas were suddenly braking at high speeds.
“The reports have often been characterized as ‘phantom braking’ by consumers,” the agency said in a filing posted to its website Thursday. “Complainants report that the rapid deceleration can occur without warning, at random, and often repeatedly in a single drive cycle.”
NHTSA said it will “determine the scope and severity of the potential problem” and “fully assess the potential safety-related issues.”
After NHTSA opened the probe into how Teslas on Autopilot handles crash scenes, the company beamed an over-the-air update to its vehicles that sought to improve how the system detects police cars and fire trucks. NHTSA asked the carmaker in October to justify its decision to make the software change without filing a recall.
Since then, Tesla has announced 11 recalls in the U.S.
Musk took issue earlier this month with media coverage of one of the safety campaigns, arguing the term recall is “anachronistic” when Tesla makes fixes with over-the-air updates. On Feb. 13, he referred to NHTSA as “the fun police” after the agency pressured the company to restrict a feature called Boombox, which enabled people to play sounds through an external car speaker.
Tesla, which has disbanded its media relations department, did not respond to a request for comment on NHTSA’s investigation.