The fix will cost Tesla about $150,000 during the second quarter, company spokeswoman Shanna Hendriks said. Tesla will inspect and reinforce the bracket in all the cars built during this time period.
This is the first recall for the Model S, blemishing a clean public record for the electric sedan that received a rare, near-perfect score from influential Consumer Reports magazine. The Palo Altro automaker twice recalled its first model, the two-door Roadster sports car.
In a statement posted on Tesla's website, CEO Elon Musk said the Model S defect emerged after the factory made body side alignment changes that weakened the bracket.
A worker at the plant's assembly line in California noticed the defect and reported it to managers, Tesla told the National Highway Traffic Safety Administration.
Tesla said in its filing with the NHTSA that it suspected that 20 percent of the 1,228 cars have welds that may not hold in the event of a crash. If the seat becomes unmoored during a crash, there is an increased chance of injury to a passenger.
Musk said there have been no customer complaints and Tesla was not aware of any injuries because of the defect. The recall was not in response to any regulatory warning, he said.
Tesla shares, which have more than tripled in the past six months, were up 2 percent to $105.88 in late morning trading.