The US government is investigating Tesla for "phantom braking"

Federal regulators this week began a preliminary investigation into an issue that causes some Tesla vehicles to brake suddenly, a phenomenon called "phantom braking."

In a document released on Wednesday, The National Highway Traffic Safety Administration says it received 354 reports from Tesla drivers who claim "unexpected brake activation" while using an advanced driver assistance system, which the company calls Autopilot.

"The complaints allege that while utilizing [Autopilot] the vehicle unexpectedly applies its brakes while driving at highway speeds," according to a NHTSA document released Wednesday.

The problem affects 2021 and 2022 Model 3s and Model Ys. The agency estimates there are 416,000 such cars on American roads.

"The rapid deceleration can occur without warning"

"Complainants report that the rapid deceleration can occur without warning, at random, and often repeatedly in a single drive cycle," according to the agency. Regulators have not documented any crashes, injuries, or fatalities.

This is the latest in a series of safety investigations

This investigation isn't the first time regulators have turned their attention to Tesla's Autopilot feature. In April 2021, the same agency launched an investigation into the system after several Teslas crashed into parked emergency vehicles. The investigation, which appears to still be ongoing, affects 750,000 vehicles. The company attempted to keep details under wraps after the NHTSA said it wasn't satisfied with Tesla's fix.

In December 2021, Tesla issued its largest recall to date due to issues with rear-facing cameras and hood latches on nearly half a million cars. The same month, the company disabled a feature that had allowed people in the vehicle to play games on a center console while the car was in motion. That move came after a similar investigation was opened.

Earlier this month, Tesla recalled roughly 54,000 cars after the NHTSA began looking into a feature of its self-driving mode that led cars to make "rolling stops" at stop signs. The company also relented after a year-long back-and-forth with the NHTSA, issuing a software update that disabled "boombox mode" on more than half a million vehicles. The fixes can be applied via over-the-air software updates using the internet. That feature, which the regulator said was a threat to pedestrian safety, let users play jingles, animal sounds, and farting noises out an exterior speaker. Asked why the feature was eliminated, Elon Musk tweeted, "The fun police made us do it (sigh)."

The fun police made us do it (sigh)

— Elon Musk (@elonmusk) February 13, 2022

Tesla still leads is EVs, but it's losing market share

It's unclear how much these recalls and updates are affecting Tesla's bottom line. The company still sells most electric vehicles in the U.S., but its competitors are eating away at its market dominance. In the first half of 2020, 80 percent of new electric vehicles sold in the U.S. were Teslas. Just one year later, that figure was 66 percent.

With analysts and industry leaders anticipating healthy growth in consumer demand for electric vehicles over the next several years, many companies have made major investments to enter the market. Audi, Nissan, Ford, and Chevrolet are each selling more than 3 percent of electric cars in the U.S. Chevy controls 10 percent of the market.

The other major U.S. automakers are also making moves. GM says it will stop selling fossil fuel-powered vehicles within thirteen years, and Toyota has pledged to invest $35 billion in electric vehicles. 

It remains to be seen if high-profile problems like Tesla's phantom braking issue will push customers to look elsewhere as more options for electric cars become available.