The 31-year-old nephew of IndyCar legend Rick Mears had lost his Richard Childress Racing seat at the end of last season.
Keyed-Up is a new organisation formed by businessman Raymond Key, whose brother Curtis runs teams in the Nationwide and Truck Series.
The Chevrolet-equipped squad intends to run the full 2010 Cup schedule, although it has yet to secure all the funding required to do so. Doug Ribert, who ran Dale Earnhardt to his first title in 1980, will be Keyed-Up's crew chief.
"We're a new team, but I feel we have everything in place to race," said Mears. "It's going to be a rewarding endeavour."
Diarra returns with injuryMears joins new Keyed-Up team
