While some plants are being idled, employees at four facilities will be working overtime, the Detroit Free Press reported.

"This is not an indication we think the market is coming back," said GM spokesman Tony Sapienza. "This is fine-tuning."

The changes include closing a truck assembly in Oshawa, Canada, May 14 instead of July 1.

Impala production at the Oshawa Consolidated plant will shut down Jan. 12 for a week. Assembly plants in Lordstown, Ohio; Orion Township, Mich.; and Kansas City, Kan., will close for a week starting Jan. 5.

Production at GM's Wentzville, Mo., plant will shut down for a week starting Dec. 8, while the Fairfax Assembly plant in Kansas City will close for two weeks starting Jan. 5 instead of just one week at the end of the month, the Free Press reported.