GM CEO Mary Barra outlined her strategic plan for the automaker earlier this year.

Mary Barra apparently is moving up in the world. In her debut year as General Motors’ chief executive she was ranked a mere second on the annual Fortune magazine list of the Most Powerful Women in business. This year, however, she surged to the top of the chart.

Barra’s freshman year was a trial by fire, among other things, Barra had to deal with revelations that GM concealed for at least a decade a deadly ignition switch defect now blamed for at least 124 fatalities. She earned kudos by issuing a corporate mea culpa and setting up a victims’ compensation fund. She also saw the maker boost sales and deliver its strongest earnings since well before its 2009 bankruptcy.

“In recent months she has beaten back headwinds from weak international markets, as sales of expensive trucks and SUVs have soared,” Fortune noted as explanation for its top pick. “Barra was one of the few female CEO participants in the viral #ilooklikeanengineer Twitter campaign, which promoted women in tech.”

Barra has received plenty of praise since being named by former GM CEO and Chairman Dan Akerson to the top post at the end of 2013. Earlier this year Barra was also ranked number one by job site glassdoor.com, which relies on anonymous reviews from current and former employees. She got an 86% approval rating.

(Despite Barra’s rejection, FCA CEO Marchionne continues pressing for merger. Click Here for more.)

Barra wants to develop a "culture of candor."

At 53, Barra has been a lifelong General Motors employee, starting out as a co-op student and working her way up from “factory rat” to a series of increasingly important roles. She broke into top management as head of GM’s Human Resources Department, a post often used as a parking spot for high-profile women who don’t really get much say in top corporate decisions. But Barra was then named the maker’s global product development chief, a critical role – especially coming out of Chapter 11.

Where Barra’s predecessor wore two hats, the 53-year old exec was named chief executive while Theodore “Tim” Solso now serves as GM’s non-executive chairman.

That still puts her at the top spot in a company that last year generated nearly $156 billion in revenues and $3.95 billion in profits. GM also was the world’s third-ranked automaker by sales, falling behind Toyota Motor Co. and Volkswagen AG.

Barra, shown with a first-gen Chevy Volt. She previously served as global product chief.

(GM beats Wall Street expectations with strong Q2 earnings. Click Here for more.)

In this year’s Fortune list, Barra nudged past long-time PepsiCo Chairman and CEO Indra Nooyi and Ginni Rometty, the CEO and Chairman of IBM. Barra is the youngest of the top five women on the list, as well.

Whether Barra will retain her king-of-the-hill ranking remains to be seen. The GM CEO faces some tough challenges in the months and years ahead. The GM ignition switch imbroglio is far from over. The maker still faces a number of lawsuits – and the likelihood of massive fines to come when the U.S. Justice Department wraps up its current criminal investigation.

The maker has fared well riding the downturn in fuel prices, thanks to its wide line-up of trucks, but it still must meet upcoming fuel economy and emissions standards, including California’s Zero-Emissions Vehicle mandate. A new version of the Chevrolet Volt plug-in – a project that began under her watch as product czar – comes to market for 2016, followed by a 200-mile Chevrolet Bolt battery-car, as well as a new Cadillac plug-in hybrid.

Perhaps one of the biggest unmet challenges, and the one that could lead to problems with investors, is the lack of momentum in GM’s stock. Even before the recent Wall Street turmoil, the maker’s shares were barely hovering around the price set during the GM IPO nearly five years ago.

But Barra is nothing if not determined to move the company forward. Her handling of the ignition switch debacle lends credence to comments she made in an interview with Fortune outlining her goal of building a “culture of candor” at GM.

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