Method for the combined identification of an inlet valve stroke phase difference (ΔEVH) and 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 air intake tract and/or of the exhaust gas in the exhaust-gas outlet tract of the respective series-production internal combustion engine are measured during operation and a corresponding pressure oscillation signal is generated from these, and wherein a crankshaft phase angle signal (KwPw) is determined at the same time, - wherein, from the pressure oscillation signal, using discrete Fourier transformation, the amplitudes of selected signal frequencies (Amp_SF_1...Amp_SF_X) of the measured pressure oscillations in relation to the crankshaft phase angle signal (KwPw) are determined, characterized by the following further steps: - on the basis of the determined amplitudes of the respective selected signal frequencies (Amp_SF_1...Amp_SF_X), determining lines of equal amplitudes (111, 121) of the selected signal frequencies (Amp_SF_1...Amp_SF_X), which lines are dependent on inlet valve stroke phase difference (ΔEVH) and outlet valve stroke phase difference (ΔAVH), using reference lines of equal amplitudes (RL_Amp_1...X), which reference lines are stored in reference line characteristic maps or determined by means of a respective algebraic model function; - determining a common intersection point of the determined lines of equal amplitudes (111, 121) of the selected signal frequencies (Amp_SF_1...Amp_SF_X) by projection into a common plane spanned by inlet valve stroke phase difference (ΔEVH) and outlet valve stroke phase difference (ΔAVH); - determining the inlet valve stroke phase difference (ΔEVH) and the outlet valve stroke phase difference (ΔAVH) from the determined common intersection point of the lines of equal amplitudes (111, 121) of the selected signal frequencies (Amp_SF_1...Amp_SF_X). - dynamic pressure oscillations, assignable to the cylinder, of the intake air in the air intake tract and/or of the exhaust gas in the exhaust-gas outlet tract of the respective series-production internal combustion engine are measured during operation and a corresponding pressure oscillation signal is generated from these, and wherein a crankshaft phase angle signal (KwPw) is determined at the same time, - wherein, from the pressure oscillation signal, using discrete Fourier transformation, the amplitudes of selected signal frequencies (Amp_SF_1...Amp_SF_X) of the measured pressure oscillations in relation to the crankshaft phase angle signal (KwPw) are determined, characterized by the following further steps: - on the basis of the determined amplitudes of the respective selected signal frequencies (Amp_SF_1...Amp_SF_X), determining lines of equal amplitudes (111, 121) of the selected signal frequencies (Amp_SF_1...Amp_SF_X), which lines are dependent on inlet valve stroke phase difference (ΔEVH) and outlet valve stroke phase difference (ΔAVH), using reference lines of equal amplitudes (RL_Amp_1...X), which reference lines are stored in reference line characteristic maps or determined by means of a respective algebraic model function; - determining a common intersection point of the determined lines of equal amplitudes (111, 121) of the selected signal frequencies (Amp_SF_1...Amp_SF_X) by projection into a common plane spanned by inlet valve stroke phase difference (ΔEVH) and outlet valve stroke phase difference (ΔAVH); - determining the inlet valve stroke phase difference (ΔEVH) and the outlet valve stroke phase difference (ΔAVH) from the determined common intersection point of the lines of equal amplitudes (111, 121) of the selected signal frequencies (Amp_SF_1...Amp_SF_X). - on the basis of the determined amplitudes of the respective selected signal frequencies (Amp_SF_1...Amp_SF_X), determining lines of equal amplitudes (111, 121) of the selected signal frequencies (Amp_SF_1...Amp_SF_X), which lines are dependent on inlet valve stroke phase difference (ΔEVH) and outlet valve stroke phase difference (ΔAVH), using reference lines of equal amplitudes (RL_Amp_1...X), which reference lines are stored in reference line characteristic maps or determined by means of a respective algebraic model function; - determining a common intersection point of the determined lines of equal amplitudes (111, 121) of the selected signal frequencies (Amp_SF_1...Amp_SF_X) by projection into a common plane spanned by inlet valve stroke phase difference (ΔEVH) and outlet valve stroke phase difference (ΔAVH); - determining the inlet valve stroke phase difference (ΔEVH) and the outlet valve stroke phase difference (ΔAVH) from the determined common intersection point of the lines of equal amplitudes (111, 121) of the selected signal frequencies (Amp_SF_1...Amp_SF_X).