The invention relates to a system for calibrating apparatus (28) for acquiring the pressure in a cylinder (10) of a motor vehicle diesel engine, of the type comprising a cylinder pressure sensor (30) associated with the cylinder and means (32) for conditioning the signal delivered by the sensor (30) as a function of conditioning parameters. The calibration system comprises means (64) for collecting a signal delivered by the cylinder pressure sensor (30), an information processing unit (34) adapted to determine the values of the conditioning parameters as a function of a polytropic thermodynamic model of the evolution of the pressure in the cylinder, a reference pressure of the pure compression phase of the cycle of the cylinder, and the signal delivered by the pressure sensor (30) and collected by the collecting means (64), and means (66) for modifying the values of the conditioning parameters in the acquisition apparatus (28) as a function of the values of the conditioning parameters determined by the information processing unit (34).