Tim Higgins
Bloomberg News

General Motors Co. said calls to a customer call center in Warren, Mich., have more than doubled during peak hours since the automaker recalled 1.6 million small cars with faulty ignition switches linked to a dozen deaths.

The so-called Customer Engagement Center, which opened last year as part of a broader effort by GM to boost customer retention and improve service, faces its first big test as the Detroit-based automaker helps customers deal with the recall.

Chief Executive Officer Mary Barra will go before U.S. House and Senate committees next week to face questions about why it took so long to recall the troubled vehicles.

The initial recall on Feb. 13 covered 778,562 Chevrolet Cobalts and Pontiac G5s and was widened less than two weeks later by more than 800,000 additional vehicles.

Barra appeared on GM’s website this week, telling customers the vehicles remain safe to drive with only the single key on a ring in the ignition.

Alicia Boler-Davis, senior vice president for global quality and customer experience, on Thursday posted a new message about GM’s efforts to assist customers with its call center.

“Since GM announced the ignition switch recall, the center has seen more than double the amount of calls during peak times from typical daily call volumes,” Boler-Davis wrote in a message.

Separately, a Texas federal judge will hold a hearing April 4 in a proposed group lawsuit against GM on whether the carmaker should issue a so-called “park it now” alert to drivers of the defective vehicles.

In a letter sent Thursday to Barra, Sen. Richard Blumenthal (D-Conn.) urged the company to immediately “issue a stronger warning to drivers,” including a notice not to operate recalled cars.