Method for the combined identification of an inlet valve stroke phase difference (ΔEVH) and of an outlet valve stroke phase difference (ΔAVH) of a cylinder of a series-production internal combustion engine during operation, wherein - dynamic pressure oscillations, assignable to the cylinder, of the intake air in the intake air tract of the respective series-production internal combustion engine are measured during operation, and a corresponding pressure oscillation signal is generated therefrom, and wherein a crankshaft phase angle signal is acquired at the same time, - wherein, from the pressure oscillation signal, the phase position (PL_SF) and the amplitude (Amp_SF) of at least one respectively selected signal frequency (SF_1...SF_X) of the measured pressure oscillations in relation to the crankshaft phase angle signal are acquired using discrete Fourier transformation, characterized by the following further steps: - acquiring, on the basis of the acquired phase position (PL_SF) and amplitude (Amp_SF) of the respective selected signal frequency (SF_1...SF_X), in each case a line of an equal phase (111, 121) and equal amplitude (211, 221) of the respectively same signal frequency (SF_1...SF_X), which line is dependent on an inlet valve stroke phase difference (ΔEVH) and outlet valve stroke phase difference (ΔAVH), using reference signs of the equal phase position (RL_Pl) and of the equal amplitude (RL_Amp) of the respective signal frequency SF_1...SF_X), which reference lines are stored in reference line characteristic diagrams or acquired by means of a respective algebraic model function; - acquiring at least one respective common intersection point of an acquired line of an equal phase position (111, 121) and of an acquired line of equal amplitude (211, 221) of the respective signal frequency (SF_1...SF_X) by projection into a common plane spanned by the inlet valve stroke difference (ΔEVH) and the outlet valve stroke phase difference (ΔAVH); - determining the inlet valve stroke phase difference (ΔEVH) and the outlet valve stroke phase difference (ΔAVH) from the acquired common intersection point of the line of an equal phase position (111, 121) and the line of equal amplitude (211, 221) of the respective signal frequency (SF_1...SF_X). - dynamic pressure oscillations, assignable to the cylinder, of the intake air in the intake air tract of the respective series-production internal combustion engine are measured during operation, and a corresponding pressure oscillation signal is generated therefrom, and wherein a crankshaft phase angle signal is acquired at the same time, - wherein, from the pressure oscillation signal, the phase position (PL_SF) and the amplitude (Amp_SF) of at least one respectively selected signal frequency (SF_1...SF_X) of the measured pressure oscillations in relation to the crankshaft phase angle signal are acquired using discrete Fourier transformation, characterized by the following further steps: - acquiring, on the basis of the acquired phase position (PL_SF) and amplitude (Amp_SF) of the respective selected signal frequency (SF_1...SF_X), in each case a line of an equal phase (111, 121) and equal amplitude (211, 221) of the respectively same signal frequency (SF_1...SF_X), which line is dependent on an inlet valve stroke phase difference (ΔEVH) and outlet valve stroke phase difference (ΔAVH), using reference signs of the equal phase position (RL_Pl) and of the equal amplitude (RL_Amp) of the respective signal frequency SF_1...SF_X), which reference lines are stored in reference line characteristic diagrams or acquired by means of a respective algebraic model function; - acquiring at least one respective common intersection point of an acquired line of an equal phase position (111, 121) and of an acquired line of equal amplitude (211, 221) of the respective signal frequency (SF_1...SF_X) by projection into a common plane spanned by the inlet valve stroke difference (ΔEVH) and the outlet valve stroke phase difference (ΔAVH); - determining the inlet valve stroke phase difference (ΔEVH) and the outlet valve stroke phase difference (ΔAVH) from the acquired common intersection point of the line of an equal phase position (111, 121) and the line of equal amplitude (211, 221) of the respective signal frequency (SF_1...SF_X).