Mr. Martin calls the G.M. headquarters the “Death Star,” after the Star Wars headquarters of Darth Vader. He says he understands the unlikely melding of cultures he is trying. “We know we’re people who don’t fit in here,” he said.

The partnership is intended to transform things as diverse as the milieu at the company’s steel-and-glass headquarters, the look of its Chevrolet cars, the dealership structure and the dashboard technology. Even the test drive is being reimagined, since young consumers find riding in a car with a stranger creepy, Scratch said.

Automakers are realizing that if they do not adjust to changing youth tastes, they “risk becoming the dad at the middle school dance,” said Anne Hubert, senior vice president at Scratch, who leads its consulting practice and works closely with G.M.

Last summer, Mr. Martin and his team temporarily transformed part of the G.M. lobby into a loftlike space reminiscent of a coffee shop in Austin or Seattle, with graffiti on the walls and skateboards and throw pillows scattered around. As part of its “Millennial-Con,” Scratch brought in viral video stars like Sergio Flores, known as the Sexy Sax Man, a musician with a mullet and a denim jacket.

Mr. Martin has recruited what he calls “insurgents,” young Chevrolet employees who are willing to change things from the inside and report to him on skeptical executives.

“How do you embed the voice of a generation in a company the size of G.M.?” Mr. Martin said, sinking into an armchair near a communal coffee maker. “It’s like moving a crater.”

But G.M. was determined to be moved. “It was the early days after bankruptcy, and we said, ‘What are we really going to do differently in the next five or 10 years?” said Mark L. Reuss, president of General Motors North America.