New York CNN  —  Federal safety regulators said they are investigating whether Tesla’s massive recall in December of essentially all of its vehicles on US roads was sufficient to fix the safety threat posed by its “Autopilot” feature. The recall of 2 million Tesla vehicles was ordered by the National Highway Traffic Safety Administration over a software update that is designed to limit the use of its Autopilot feature. The NHTSA had said in December that the two-year probe of roughly 1,000 crashes in which the feature was engaged found it gave drivers a false sense of security and could be easily misused in certain dangerous situations when the technology may be unable to safely navigate the road. The NHTSA said late Thursday that Tesla’s software update recall requires the owner to opt in and allows a driver to readily reverse it. The NHTSA said it is “therefore opening this recall query investigation to further evaluate the adequacy of the remedy.” This latest probe is a blow to Tesla and CEO Elon Musk’s efforts to market the cars as effectively able to drive themselves, a luxury feature that makes the vehicles and the company more valuable. Earlier this week, Musk claimed the company would soon unveil plans for a fleet of “robotaxis,” a service that would give Tesla owners the option to earn money by having their vehicles provide driverless taxi rides when the owners aren’t using them. Tesla and Musk have claimed that cars using Autopilot features — which are available on virtually all Teslas, as well as the more robust “Full Self Driving” feature that comes at a premium price — are safer than human drivers. But NHTSA said its investigation identified at least 13 crashes involving one or more fatalities and many more involving serious injuries in which “foreseeable driver misuse” of the system played an apparent role. LONDON, ENGLAND - APRIL 15: Rows of new Tesla cars are seen in a holding area near a customer collection point on April 15, 2024 in London, England. According to a memo sent to staff today, the company will reduce its global workforce by 10%. As of last December, it had just over 140,000 employees according to its last annual report. Leon Neal/Getty Images Related article Tesla’s earnings plunge, but the company promises cheaper car model The software update ordered in December was designed to give Tesla drivers more warnings when they are not paying attention to the road while using the Autopilot’s “Autosteer” function. Those notifications were to remind drivers to keep their hands on the wheel and pay attention to the road, according to a statement at the time from NHTSA. After the recall, Tesla vehicles with Autosteer turned on were supposed to check on the driver’s attention level more routinely. The feature might disengage when it determines the driver isn’t paying attention, the car is approaching traffic controls or it’s off the highway when Autosteer alone isn’t sufficient to drive the car. Despite the Autopilot name and the way Tesla is marketing the feature, Tesla’s owners manuals say: “Autosteer is intended for use only on highways and limited-access roads with a fully attentive driver.” Tesla, which has not responded to requests for comment from CNN for several years, did not respond to a request for comment on this latest investigation.