The PCM block controls a time interval of an entrance signal of the sensor of position of the crankshaft. The PCM block calculates change of a time interval for each cylinder. If change of a time interval exceeds previously programmed values, the PCM block finds the admission of ignition in the corresponding cylinder. In operating time of the engine the PCM block considers the number of admissions of ignition which happened for each 200 and 1000 turns of a bent shaft, and calculates coefficient of the admission of ignition for each turn of a bent shaft. If the relation exceeds previously programmed values, the PCM block decides that there was an admission of ignition which can lead to damage of catalytic converter or influence characteristics of emissions.