The automaker says a software glitch could prevent the defroster from clearing the windshield in the 2011 Buick LaCrosse and the Cadillac SRX.
Dealers are expected to begin notifying owners about repairs later this week.
Owners can contact Buick at 1-866-608-8080, Cadillac at 1-866-982-2339, or both at the owner center, www.gmownercenter.com .