Kyle Busch was in control but was leaking oil on the track and skidded sideways coming out of the first turn of the final lap. Keselowski's No. 2 Dodge caromed off the side of the No. 18 Toyota and Ambrose followed Keselowski through.
Ambrose and Keselowski battled side by side the rest of the way around the 2.45-mile layout, with neither giving ground before Ambrose moved in front heading to the checkered flag.
Jimmie Johnson was third, followed by Sonoma winner Clint Bowyer and Sam Hornish Jr., giving Dodge two in the top five.
Greg Biffle was sixth, followed by Busch, Matt Kenseth, Regan Smith and Martin Truex Jr. rounded out the top 10.