Catalytic converter early light off using cylinder deactivation

A vehicle includes an engine that has a plurality of cylinders and that generates exhaust gas. A catalytic converter reduces harmful emissions from the exhaust gas after achieving a light off temperature. A controller is connected to the engine and the catalytic converter. The controller deactivates the cylinder(s) of the engine before the catalytic converter achieves the light off temperature if the engine is operating at idle or low load. The controller waits a first period before deactivating the cylinder(s). The controller optimizes engine operating parameters to reduce a second period that is required to achieve the light off temperature. A temperature sensor is connected to the controller and senses ambient temperature. The controller does not deactivate the cylinders if the ambient temperature is below a first predetermined temperature. The controller activates all of the cylinders if the engine is operating at high load.