Leimer joined the team for the GP2 Final event in Abu Dhabi at the end of 2011, which he won overall, but could not translate that form into a title challenge last year, finishing seventh in the standings.
But team boss Alfonso de Orleans-Borbon is confident Leimer will be a championship threat this season.
"He has already showed last year that he is one of the best up and coming drivers," said de Orleans-Bourbon.
"In 2012 he finished on the podium six times and led races for many laps.
"What makes me the happiest is that we can build on what we learned together in 2012 and this makes me confident for the upcoming season. It is our goal that Fabio wins the championship."
Leal was Leimer's team-mate in Rapax in 2011, before returning to his '10 Auto GP squad Trident last year. The Colombian has yet to take a top-six finish in GP2.
"2013 will be the year where we will see his full potential," said de Orleans-Borbon.
"He has the ability and the determination to get the job done."
