Tesla is being investigated by NHTSA due to a software update that Tesla models were offered earlier this year. According to the report, the software update which was supposed to address the issue of battery fires might have done more than just prevent batteries from catching fire.
Some owners reported that after the update, they notice that their vehicle seems to have a decrease in range and some of them have even sued Tesla for it. NHTSA was asked to investigate and see if Tesla used the software to hide a deeper issue with the tesla models.
When the software was released, Tesla did say that it would change some of the settings in the battery management software that governs the charging and thermal control but they did not offer any additional information or stated that it will affect the range of the vehicles.
It is now up to NHTSA to look into the matter.