A method to detect whether combustion is taking place in an internal combustion engine of a hybrid vehicle during operation of the hybrid vehicle, whereby a decoupler is provided between the internal combustion engine and an electric machine that serves to power the hybrid vehicle, comprising opening the decoupler between the internal combustion engine and the electric machine, receiving a speed signal when the decoupler is open, said signal indicating a rotational speed of the internal combustion engine when the decoupler is open, and determining, on the basis of the speed signal when the decoupler is open, whether combustion is taking place in the internal combustion engine. The present invention also relates to a control device to carry out the method according to the invention.