General Motors is giving Ammirati Puris Lintas, New York, "creative consulting" work for its Pontiac Division best-seller, the Grand Am, as well as for GMC's Jimmy. An executive familiar with the assignment said there's been no promise Ammirati would get more work if it performs well. Pontiac agency D'Arcy Masius Benton & Bowles is said to be worried the move may signal more losses on the account. GMC shop McCann-Erickson Worldwide claimed Ammirati's work is a new project. The move shows Ron Zarrella, group VP-sales, service and marketing, is serious about creating strong brand messages.