Abstract: A control system for a hybrid electric vehicle having an electric drive module and an internal combustion engine with an exhaust system. The control system includes one or more oxygen (O2) sensors disposed proximate to a catalytic converter in the exhaust system, the one or more O2 sensors each being configured to measure an O2 level of exhaust gas produced by the engine. A controller is in signal communication with the one or more O2 sensors and programmed to detect the hybrid electric vehicle is keyed on, determine the hybrid electric vehicle is keyed to run in an electric vehicle (EV) mode without the engine started, and initiate an O2 sensor heating mode to heat the one or more O2 sensors to a predetermined target temperature prior to the engine starting. The predetermined target temperature is operable for closed loop fueling feedback control, to thereby reduce exhaust emissions.

Abstract: An engine control system includes one or more oxygen (O2) sensors disposed proximate to a three-way catalytic converter (TWC) in an exhaust system of the vehicle, the one or more O2 sensors each configured to measure an O2 level of exhaust gas produced by the engine. A controller is in signal communication with the one or more O2 sensors and programmed to detect a fuel shut-off (FSO) event where the engine ceases providing fuel to the engine, determine an accumulated gas flow through the TWC during the FSO event, determine the FSO event has ended, initiate an open loop fuel enrichment mode where the engine is supplied with a first fuel enrichment level having a first rich fuel/air ratio, and subsequently initiate a closed loop fuel enrichment mode where the engine is supplied with a second fuel enrichment level having a second rich fuel/air ratio, to thereby reduce NOx emissions.