System and method for controlling an automatic engine stop-start accumulator

A method for controlling a powertrain in a motor vehicle, the powertrain having an engine and a transmission with a solenoid in fluid communication with an accumulator and having a plurality of torque transmitting devices operable to provide at least a plurality of gear speeds, the method comprising:

• determining a first set of vehicle status indicators;
• determining a set of transmission status indicators including a sensed pressure in the accumulator and a temperature of a hydraulic fluid in the transmission;
• shutting off the engine of the motor vehicle as a function of the first set of vehicle status indicators;
• inhibiting shutting off the engine of the motor vehicle as a function of the set of transmission status indicators;
• determining a second set of vehicle status indicators;
• opening the solenoid to discharge the accumulator as a function of the second set of vehicle status indicators;
• commanding the transmission to provide a gear speed of the plurality of gear speeds;
• engaging a first set of the plurality of torque transmitting devices required to provide the commanded gear speed;
• starting the engine;
• setting an engine timer to a zero value;
• incrementing the engine timer;
• calculating a time threshold based on a requested power demand to the powertrain;
• engaging a second set of the plurality of torque transmitting devices required to provide the commanded gear speed if the engine timer is greater than the time threshold;
• and
• engaging a third set of the plurality of torque transmitting devices required to provide the commanded gear speed if a second, higher gear speed than the commanded gear speed has been subsequently commanded.