A method for starting and operating an engine of a mild hybrid vehicle following start-up is disclosed for an engine having low and high voltage starting devices, and controlled by an electronic controller. The method comprises using the high voltage starting device as a motor to crank the engine whenever possible so as to partially discharge a high voltage battery. The method further comprises using the high voltage starting device as a generator after starting the engine if the exhaust gas temperature needs to be increased so as to assist with light-off of one or more exhaust gas after treatment devices.

An automatic engine start/stop system and method which are compatible with recent engine requirements of a pre-lube period before engine crank, is disclosed. A temp-start controller is used to read inputs such as ambient temperature, oil temperature and engine RPMs, to determine proper conditions for engine cranking. A pre-lube pump is activated by the controller for up to 45 seconds, or a desired period of time, before engine crank. A glow plug pre-heating step may be performed as well, if necessary.

A system includes an ultra-capacitor and battery system comprising a battery, a DC-DC converter, and an ultra-capacitor. An auto stop/start module is configured to perform an auto stop event of an engine of a vehicle and an auto start event of the engine of the vehicle based on operating parameters while an ignition is ON. A voltage monitoring module is configured to, in response to a request for an auto start event, selectively discharge the ultra-capacitor during cranking for the auto start event, accumulate a plurality of voltage delta values while the ultra-capacitor discharges during the cranking, and selectively disable the auto stop/start module based on the plurality of voltage delta values.