Engine-off auxiliary hydraulic pressurization system and method for a transmission

An auxiliary hydraulic pressurization system for use with a vehicle including a transmission having a hydraulic reservoir, a hydraulic circuit, and a main pump, the auxiliary hydraulic pressurization system comprising:

• an auxiliary pump with a low side adapted to be coupled to the hydraulic reservoir and a high side adapted to be coupled to the hydraulic circuit;
• a controller electrically connectable to the auxiliary pump and configured to turn on the auxiliary pump in response to receipt of a signal indicating that the vehicle is in a stop condition to maintain hydraulic pressurization of the hydraulic circuit of the transmission when the vehicle is in the stop condition, and
• a bypass valve coupled to the high side of the auxiliary pump and adapted to be coupled to the hydraulic circuit, wherein the bypass valve is biased to a closed position and is configured to open to an open position in response to a pressure of a fluid from the high side of the auxiliary pump matching a threshold bypass pressure,
• wherein the bypass valve remains in the open position while the pressure of the fluid is greater than the threshold bypass pressure to prevent the auxiliary pump from providing hydraulic fluid to the transmission at a pressure greater than the threshold bypass pressure and wherein the bypass valve is coupled to the hydraulic reservoir to establish a bypass path that transmits fluid from the auxiliary pump to the hydraulic reservoir when fluid moves from the auxiliary pump toward the hydraulic circuit at the pressure greater than the threshold bypass pressure, and
• a check valve coupled to the high side of the auxiliary pump and adapted to be coupled to the hydraulic circuit, the check valve configured to block backflow from the hydraulic circuit through the high side of the auxiliary pump.