TOLEDO, Ohio — Auto-parts maker Dana Corp. said yesterday it will restate its earnings for the past six quarters to fix improper accounting and will withdraw its profit forecast for 2005. The news sent its stock tumbling for the second time within a month.

The company's stock has lost half of its value since mid-September. Shares dropped 33 percent yesterday afternoon.

Dana said the restatements for all of 2004 and the first two quarters of 2005 stem primarily from improper accounting for issues involving customer pricing and its commercial vehicle business.

This comes just weeks after Dana said it was cutting its profit outlook for this year in half.

The Toledo-based company, which earlier had reported profit of $82 million for 2004, did not say how much earnings will be affected. It also will delay its third-quarter earnings announcement, which was scheduled for this week. The company did not immediately return a message yesterday.

The announcement is another blow to the struggling auto parts supplier industry. Delphi Corp., the largest U.S. auto supplier, filed for bankruptcy Saturday and is expected to cut jobs and close some of its 31 U.S. plants.

The FBI and the Securities and Exchange Commission have been investigating Delphi's accounting practices for several months. Delphi had restated its earnings for the past five years after conducting an internal investigation.

Dana said that it believes it has weaknesses in its internal control over financial reporting. The company has not determined whether the additional revisions to its earnings will be necessary.

The company's stock fell $3.07 to $6.12 a share in afternoon trading yesterday on the New York Stock Exchange, below the previous 52-week low of $8.79.

Its stock fell last month by 23 percent after it announced it was cutting its profit forecast for the year. The company's shares had been as high as $18.59 during the past 52 weeks.

Dana, which makes brakes, axles and other parts, said that soaring energy and steel costs were to blame.

The company said last month it will be making significant changes to improve its financial performance.