Edward E. Whitacre Jr., who took over in December, will replaced by Daniel F. Akerson, a GM board member. Analysts say the firm’s second consecutive quarterly gain is a positive step toward an anticipated initial public stock offering.

General Motors Co. posted a second-quarter profit of $1.3 billion Thursday and announced the retirement of Edward E. Whitacre Jr., the automaker’s chairman and chief executive.

Whitacre, who became CEO just this past January, said he would step down in September to be replaced by Daniel F. Akerson, a GM board member and managing director of the Carlyle Group buyout fund. Ackerson will replace Whitacre as chairman by year’s end.

“Ed Whitacre was exactly what this company needed, at exactly the right time,” said Pat Russo, lead director on the GM board. “He simplified the organization, reshaped the company’s vision, put the right people in place and brought renewed energy and optimism to GM.”  Russo also added that Akerson “brings broad business experience, decisive leadership and continuity” to the job.

Akerson, 61, joined the GM board in July 2009. Besides the Carlyle Group, he has also worked in telecommunications, serving as chairman and chief executive of XO Communications and at Nextel Communications. He was also chairman and CEO of General Instrument Corp.

“There are remarkable opportunities ahead for the new GM, and I am honored to lead the company through this next chapter,” Akerson said. “Ed Whitacre established a foundation upon which we will continue building a great automobile company.”