A method for storing data concerning an operating fault of a device, wherein the recorded data include in particular a minimum value and a maximum value of a characteristic parameter of the operating mode of the device. The method includes an updating phase, performed when the fault occurs, which includes an operation that updates the minimum value and/or the maximum value based on the current value of the parameter. The updating phase may also include updating an occurrence number. The method may also include an initializing phase, during which a reference image of the parameters of the device is stored. The method is applicable in particular to the diagnosis of a vehicle engine-transmission unit.