A U.S. auto safety regulator said on Friday it is opening an investigation into 73,000 Chevrolet Volt plug-in hybrid cars over reports of abrupt loss of power, failures to restart and other issues.

According to The Iran Project The National Highway Traffic Safety Administration said it was opening the preliminary evaluation into the 2016 through 2019 model year Chevrolet Volt after 61 complaints tied to the battery energy control module (BECM). Some complaints reported there was little to no warning before the loss of operating power or reduced power mode occurred.

General Motors (GM.N) previously issued a technical service bulletin saying if vehicles fail to restart, the BECM may need to be replaced and reprogrammed but has not recalled vehicles, NHTSA said. GM ended production of the Volt in early 2019.

GM said it was cooperating with the NHTSA investigation and said it believes it has "taken appropriate action to remedy customer concerns related to the battery energy control module but will continue to support the agency’s review of the matter."
NHTSA said the issue may pose a safety risk if vehicles cannot move with the flow of surrounding traffic and is more serious depending on a stalled vehicle’s ability to restart.

Some owners have told NHTSA they have waited months or been unable to get replacement battery modules after experiencing the issue. GM said it has a sufficient replacement parts in its supply pipeline.

An owner in Los Angeles said the Volt "suddenly, and unexpectedly lost propulsion while driving. The vehicle is no longer able to turn on or drive."
Another owner reported the Volt would not drive more than over 35 miles per hour on the highway "and it stops driving on electricity randomly."