A controller for a drive train of a motor vehicle having an engine and an automatic transmission, includes an engine controller through which variables that influence the torque of the engine are controlled, a transmission controller through which shift processes of the automatic transmission are controlled, and an interface which connects the engine controller and the transmission controller to one another and through which data are transmitted to give the vehicle good handling. The interface is used to transmit a status signal which signals to the transmission controller that catalytic converter regeneration is taking place, and through which a shift process in the transmission is changed in the transmission controller.