A method of operating a hybrid vehicle when an internal combustion engine is not running includes heating a flow of air flowing through an exhaust gas treatment system of the internal combustion engine that is supplied by an air pump with a heating module and a hydrocarbon injector. The heating module heats an electrically heated catalyst of the exhaust gas treatment system in preparation for starting the internal combustion engine. Additionally, thermal energy is recovered from the flow of air downstream of the electrically heated catalyst and transferred to at least one other vehicle system to provide thermal energy to the vehicle system, such as an engine coolant for a cabin heating system or a transmission fluid for a drivetrain transmission system.