Diallo joined Honda in 2001 through the company's National Trainee program. During his 23-year tenure at the OEM, Diallo held numerous leadership roles including vice president of Auto Sales, responsible for Honda and Acura sales in the U.S., Caribbean, and Central America, including Market Representation, Vehicle Distribution and Logistics, public relations, dealer communications, and sales training; vice president, Auto Operations, overseeing Product Planning, Sales & Production Planning and Logistics; and assistant vice president of Acura National Sales, Incentive and Strategy among other positions.