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Mr. Akerson said Mr. Liddell was a major contributor to GM during a pivotal time in company history.

“He guided the company’s IPO process and established a good financial foundation for the future,” he said.

Mr. Ammann, 38, joined GM as treasurer in March 2010. Before GM, he was managing director and head of industrial investment banking for Morgan Stanley. His replacement will be announced later.

Mr. Ammann told reporters that he is committed to GM for the long term, and he agrees with Mr. Liddell’s financial strategies. Investors, he said, could expect “more of the same.”

Some industry analysts wonder if Mr. Liddell’s departure was prompted by GM’s decision in the past two months to raise such incentives as low-interest loans and lease deals — moves that could hurt GM’s bottom line in the first quarter.

But Mr. Liddell said his leaving has nothing to do with the company’s first-quarter performance, and Mr. Akerson said the company was off to a fast start for the quarter.

GM was plagued with financial reporting problems heading into and emerging from bankruptcy protection. Going into its IPO last year, the company said weaknesses in its financial controls meant many of its numbers could not be considered reliable.

Steven Rattner, former head of the government’s autos task force, has said that GM had the weakest finance operation that task force members had seen in a major company.

But just two weeks ago, when GM released its 2010 earnings, the company said those problems had been fixed.

GM reported net income of $4.7 billion last year, fueled by strong sales in China and the United States as the global auto market began to recover. It was the company’s best performance since earning $6 billion in 1999 during the height of the pickup truck and SUV sales boom.

GM accepted nearly $50 billion in government help to help it survive in 2009, but the company has since made an impressive recovery, with global sales growing 12 percent last year.

The company still must pay back more of its rescue aid. GM’s owners — the U.S. Treasury Department, the Canadian and Ontario governments, and a union health care trust fund — sold common stock in the November IPO. The U.S. government got $13.5 billion from the sale and will have to sell its remaining shares for $53 each to break even on its aid to GM.

AP auto writer Sharon Silke Carty in Detroit contributed to this report.