A method of operating a vehicle powertrain includes determining a selected powertrain operational mode. A demand fraction is determined. An internal combustion engine (ICE) is to output a maximum power when a gaseous fuel is conveyed to an injector of the ICE at a source pressure greater than a cutoff pressure. The source pressure in a container in fluid connection with the injector is determined. The gaseous fuel is received at the source pressure by the injector to inject the gaseous fuel into the ICE for combustion in response to the source pressure, demand fraction, or selected powertrain operation mode meeting a first set of criteria. The injector is prevented from injecting the gaseous fuel into the ICE and the powertrain is driven from an alternative power source in response to the source pressure, demand fraction, or selected powertrain operation mode meeting a second set of criteria.