Jackson, who was promoted to the top advertising spot in March, 2006, as part of a company shakeup to turn around a sales slump, replaced Brent Dewar, who was reassigned to VP/field service and parts.
Before his ascendance to the top marketing role Jackson, 50, had been GM's western regional sales marketing director since 2002, overseeing sales, marketing and distribution in 16 western states.
Jackson's promotion to the top spot reflected both the importance of California as a conquest market for the automaker and Jackson's work in that region. He was credited with reinvigorating the market with a number of grassroots, Internet and dealer initiatives.
GM CEO Rick Wagoner has said Jackson, through his relations with dealers, and local market initiatives, helped GM gain lost market share on the West Coast.
He was succeeded in the western regional position by Susan Docherty, who had been Hummer's general manager.
Ryndee Carney, a spokesperson for General Motors, said that no replacement has been found, but that, for the time being, Mark R. LaNeve, GM's North American VP, vehicle sales, service and marketing, will handle Jackson's duties.
"The people who reported to Mike will report to Mark LaNeve," she said, adding that he is leaving for personal reasons. "His family has remained in southern California; the grind of back and forth has been a lot of pressure and wear and tear on him."
Jackson came to GM from stints at Coca-Cola, Pepsi-Co, and Coors, where he was VP/marketing development for U.S. distribution.