A vehicle includes an engine having a crankshaft, a transmission having an input, and a torque converter mechanically coupled to the input. The vehicle further includes an electric machine mechanically coupled to the torque converter, a clutch configured to mechanically couple the electric machine and crankshaft, and one or more controllers. The one or more controllers are programmed to, in response to the transmission being in a drive or reverse gear and a speed of the vehicle being less than a predetermined value in an absence of driver demand, control the electric machine to achieve a target speed to cause the torque converter to output torque such that the speed of the vehicle approaches a generally constant speed less than or equal to the predetermined value when the vehicle is on a generally flat grade.