Federal regulators require Tesla Inc. Around 158,000 cars have been recalled over safety concerns in what may amount to one of the electric carmaker’s biggest safety measures.

In a letter dated January 13th, the National Highway Traffic Safety Administration asked Tesla to recall some luxury Model S sedans and Model X sports cars. The NHTSA requested the recall because automotive touch screens can malfunction after a few years of use, affecting safety functions such as defogging and backup cameras.

Some auto safety recalls collide with millions of vehicles. Although humbled by historical numbers, the measure would mark a relatively big recall for Tesla, which has far fewer cars on the road than some competitors. Silicon Valley auto maker Delivered nearly 500,000 vehicles worldwide Last year, nearly 205,600 of them were in the United States, according to market research firm Motor Intelligence. Tesla does not separate its sales by region.

Tesla does not have to recall the vehicles, although the NHTSA said in the letter that if the car maker did not take the action, it should provide an explanation for its decision. The agency can then escalate the matter to a public hearing and ultimately seek a subpoena through the courts.

Guidehouse Insights analyst Sam Abu Al-Samed said the subpoena was large and could cost $ 300 million to $ 500 million to process.