A vehicle includes an inverter, a pump, a buck converter, and a controller. The inverter has an input connected to a battery and an output connected to an electric machine. The inverter is configured to convert power between DC electrical power at the input and AC electrical power at the output. The pump is configured to circulate lubricating fluid within a transmission. The buck converter is configured to deliver DC electrical power from the inverter to the pump. The controller is programmed to, in response to the electric machine delivering AC electrical power to the inverter during a towing condition of the vehicle while the vehicle is shutdown, operate the buck converter to power the pump.