The company said Sunday that Joel Ewanick has elected to resign and his decision is effective immediately. The 52-year old executive joined the Detroit auto maker in 2010 to oversee marketing for the company's North American unit and was promoted within months to head its global marketing business.
Ewanick is an auto industry veteran, having worked for Nissan North America and Hyundai Motor America.
The announcement comes after G.M. made several major changes to its advertising approach. The company announced this spring it would pull ads from Facebook, saying they weren't effective. It also decided it wouldn't advertise at the Super Bowl this February due to price hikes.