Abstract: A powertrain system includes a hybrid transmission coupled to an engine and an auxiliary hydraulic pump. The auxiliary hydraulic pump is commanded to operate at a predetermined speed only when enable criteria are met. An engine-off state is inhibited based upon a difference between a commanded speed and a monitored operating speed of the auxiliary hydraulic pump.

Abstract: A method for detecting speed faults in a hybrid powertrain having engine and electric machine speed inputs includes directly sensing the engine and machine speeds and performing comparisons of sensed engine speed with engine speed determined based upon the machine speeds.

Abstract: A system for robust fault detection in an electrically variable, hydraulically controlled transmission includes independently monitoring hydraulic pressure within a hydraulic control circuit and electric machine rotation for detecting clutch state faults.

Abstract: Monitoring operation of an electromechanical transmission having a hydraulic circuit with flow management valves and pressure control solenoids to actuate clutches and pressure monitoring devices to monitor the hydraulic circuit is provided. The transmission operates in fixed gear and continuously variable operating range states. The method comprises controlling position of one of the flow management valves to control operation in one of the operating range states. A fault is detected in the one of the flow management valves based upon outputs of the pressure monitoring devices during steady state operation in one of the continuously variable operating range states. A fault is detected in the one of the flow management valves based upon the output of one of the pressure monitoring devices during a transition in the flow management valve.