Marketing exec Joel Ewanick is on the move again, this time to Detroit.

Forgive the post office if they have a hard time forwarding Joel Ewanick’s e-mail.  The former Hyundai marketing executive has been moving fast, lately, and is now on the road again.

The 49-year-old Ewanick will take the top marketing position at General Motors, effective May 24, directly reporting to GM’s North American President Mark Reuss.  It puts Ewanick into a critical position at a time when GM is struggling to not just kick-start sales but shift its focus from eight North American brands to the four that survived its bankruptcy, last year.

Working out of the Detroit Renaissance Center, Ewanick will take over the position held, since last year, by General Motors’ top-ranking woman executive, Susan Docherty.  The surprise appointment appears to underscore a promise by GM CEO Ed Whitacre that top management would be held accountable for the company’s performance.

It’s a big move for Ewanick, but an even bigger surprise for Nissan, which thought the boyish-looking executive would be heading its marketing operations.

Ewanick is the man behind the hugely-successful Hyundai Assurance Program –which promised to cover a Hyundai buyer who became unemployed, even buying back the vehicle, if necessary.  It earned him extensive kudos, among others being named Forbes’ Chief Marketing Officer of the Year.

But insiders say that after three years with the Korean maker, Ewanick began to chafe under the dictates of Hyundai’s Korean management and, adds a close source, “Joel gets bored easily.  He’s always looking for a new challenge.”

Whatever the final reason, Ewanick announced barely two months ago that he would decamp from California and head to Nashville, where he began working, on March 22, as vice president of marketing for the Japanese maker.

It was viewed as a solid move for Nissan, which has continued to struggle, both internally, and on the U.S. market, ever since it moved its headquarters to Tennessee, several years ago.

But it appears unlikely Ewanick will have enough tenure to ever collect from the Nissan pension program, now that he has agreed to jump ship, yet again.

The shift to GM is a surprise on several counts, not just because Ewanick is leaving Nissan, but because he is replacing Susan Docherty, who had become one of GM’s top executives after the company emerged from bankruptcy, last July.

But the top sales and marketing posts have been a place of turmoil at GM.  Initially, Bob Lutz, the company’s now-retired Vice Chairman, was to run marketing, and Docherty was installed as head of sales.  Last December, following the ouster of former CEO Fritz Henderson, marketing duties were passed on to Docherty.  She subsequently gave up responsibility for North American sales, an assignment passed onto North American President Reuss.

Last month, CEO Whitacre told TheDetroitBureau.com this game of corporate musical chairs was largely completed, but the Ewanick appointment suggests that Whitacre still isn’t happy with the GM line-up, despite last month’s double-digit sales gains.

How much time Ewanick will be given to get GM’s marketing operations in order remains to be seen.  As for Docherty, the automaker says it will later announce a new assignment, though such statements often come before an executive departs for new climes.  There may be a job available at Nissan.