A method of detecting a deviation in operation of a pressure sensor having a sensor specific sensitivity ( s m) for converting electric signal obtainable from the sensor into pressure, in internal combustion piston engine, which method comprising - reading a first measurement signal (p 1,m) and a second measurement signal (p 2,m) from the pressure sensor at a first crank angle position and at a second crank angle position, respectively, during compression stroke of a cylinder of the engine when the combustion chamber is closed, - determining a first volume (V 1) of the combustion chamber at the first crank angle position, and - determining a second volume (V 2) of the combustion chamber at the second crank angle position, determining an estimated isentropic proportionality constant C by applying the values of the measurement signals and respective combustion chamber volumes to the formula C = ∑ V − γ ⋅ ∑ p m − ∑ p m ⋅ V − γ ⋅ ∑ 1 ∑ V − γ ⋅ ∑ V − γ − ∑ V − 2 γ ⋅ ∑ 1, in which γ is the ratio of the heat capacity at constant pressure to heat capacity at constant volume of gas in the combustion chamber during compression, and when using electric signal of the first and the second measurement signal obtained from the pressure sensor, determining an estimated sensor sensitivity and use the estimated sensor sensitivity for detecting a deviation in the sensor measurement signal sensitivity by performing a quality check in respect to the sensor specific sensitivity ( s m). characterized by determining the estimated sensor sensitivity using the formula s = C ⋅ V 2 − γ − V 1 − γ U 2 − U 1 where C is the estimated isentropic proportionality constant, V is the cylinder volume, and γ is the ratio of the heat capacity at constant pressure (C p) to heat capacity at constant volume (Cv), or alternatively when alternatively using pressure signal (p) from the first and the second measurement signal converted from an electric signal, determining an estimated sensor sensitivity using the formula s = s m ⋅ C ⋅ V 2 − γ − V 1 − γ p 2, m − p 1, m, where C is the estimated isentropic proportionality constant, V is the cylinder volume, γ is the ratio of the heat capacity at constant pressure (C p) to heat capacity at constant volume (C V), and s m is the constant, sensor specific sensitivity used during the measurement wherein thus estimated sensor sensitivity S is used for detecting a deviation in the sensor measurement signal sensitivity by performing a quality check in respect to the sensor specific sensitivity ( s m). - reading a first measurement signal (p 1,m) and a second measurement signal (p 2,m) from the pressure sensor at a first crank angle position and at a second crank angle position, respectively, during compression stroke of a cylinder of the engine when the combustion chamber is closed, - determining a first volume (V 1) of the combustion chamber at the first crank angle position, and - determining a second volume (V 2) of the combustion chamber at the second crank angle position, in which γ is the ratio of the heat capacity at constant pressure to heat capacity at constant volume of gas in the combustion chamber during compression, and when using electric signal of the first and the second measurement signal obtained from the pressure sensor, determining an estimated sensor sensitivity and use the estimated sensor sensitivity for detecting a deviation in the sensor measurement signal sensitivity by performing a quality check in respect to the sensor specific sensitivity ( s m). characterized by determining the estimated sensor sensitivity using the formula s = C ⋅ V 2 − γ − V 1 − γ U 2 − U 1 where C is the estimated isentropic proportionality constant, V is the cylinder volume, and γ is the ratio of the heat capacity at constant pressure (C p) to heat capacity at constant volume (Cv), where C is the estimated isentropic proportionality constant, V is the cylinder volume, and γ is the ratio of the heat capacity at constant pressure (C p) to heat capacity at constant volume (Cv), or alternatively when alternatively using pressure signal (p) from the first and the second measurement signal converted from an electric signal, determining an estimated sensor sensitivity using the formula s = s m ⋅ C ⋅ V 2 − γ − V 1 − γ p 2, m − p 1, m, where C is the estimated isentropic proportionality constant, V is the cylinder volume, γ is the ratio of the heat capacity at constant pressure (C p) to heat capacity at constant volume (C V), and s m is the constant, sensor specific sensitivity used during the measurement determining an estimated sensor sensitivity using the formula s = s m ⋅ C ⋅ V 2 − γ − V 1 − γ p 2, m − p 1, m, where C is the estimated isentropic proportionality constant, V is the cylinder volume, γ is the ratio of the heat capacity at constant pressure (C p) to heat capacity at constant volume (C V), and s m is the constant, sensor specific sensitivity used during the measurement wherein thus estimated sensor sensitivity S is used for detecting a deviation in the sensor measurement signal sensitivity by performing a quality check in respect to the sensor specific sensitivity ( s m).