Method for characterising one or more faults in a system grouping together a plurality of internal physical quantities and delimited by a plurality of boundary physical quantities, the system being modelled by a healthy model establishing relationships linking said internal physical quantities with one another and with the boundary physical quantities in the absence of a fault, a fault being defined as a negative change in the relationships linking said internal physical quantities with one another and with the boundary physical quantities with respect to the healthy model, said system being provided with a plurality of sensors measuring values of internal physical quantities and external physical quantities, the method comprising the implementation of the steps of: • determination of a vector of the measured measurements of a set of internal physical quantities by reading the values of internal physical quantities measured by the sensors, • determination of a vector of actual symptoms by the difference between the vector of measured measurements and a vector of expected measurements, said vector of expected measurements grouping together values of internal physical quantities obtained by simulation of the healthy model from the boundary physical quantities, characterised in that the method further includes the implementation of the steps of: • for a determined number of iterations: ∘ determination of a proposed vector of faults from the current vector of faults by a pseudo-random sampling using a probability law on each of the fault values of the current vector of faults, a vector of faults grouping together values representative of one or more faults; ∘ determination of the probability of acceptance of the proposed vector of faults using the vector of actual symptoms, a fault matrix, the current vector of faults, the probabilistic distribution of the vector of actual symptoms knowing the current vector of faults, the proposed vector of faults, the probabilistic distribution of the vector of actual symptoms knowing the proposed vector of faults, and an a priori probability distribution of occurrences of the values of the fault vector, said fault matrix grouping together the consequences of each fault on the internal physical quantities ∘ replacement or not of the current vector of faults by the proposed vector of faults as a function of the probability of acceptance of the proposed vector of faults, • characterisation of a fault by recording the number of iterations having involved said fault in a current vector of faults. • determination of a vector of the measured measurements of a set of internal physical quantities by reading the values of internal physical quantities measured by the sensors, • determination of a vector of actual symptoms by the difference between the vector of measured measurements and a vector of expected measurements, said vector of expected measurements grouping together values of internal physical quantities obtained by simulation of the healthy model from the boundary physical quantities, • for a determined number of iterations: ∘ determination of a proposed vector of faults from the current vector of faults by a pseudo-random sampling using a probability law on each of the fault values of the current vector of faults, a vector of faults grouping together values representative of one or more faults; ∘ determination of the probability of acceptance of the proposed vector of faults using the vector of actual symptoms, a fault matrix, the current vector of faults, the probabilistic distribution of the vector of actual symptoms knowing the current vector of faults, the proposed vector of faults, the probabilistic distribution of the vector of actual symptoms knowing the proposed vector of faults, and an a priori probability distribution of occurrences of the values of the fault vector, said fault matrix grouping together the consequences of each fault on the internal physical quantities ∘ replacement or not of the current vector of faults by the proposed vector of faults as a function of the probability of acceptance of the proposed vector of faults, ∘ determination of a proposed vector of faults from the current vector of faults by a pseudo-random sampling using a probability law on each of the fault values of the current vector of faults, a vector of faults grouping together values representative of one or more faults; ∘ determination of the probability of acceptance of the proposed vector of faults using the vector of actual symptoms, a fault matrix, the current vector of faults, the probabilistic distribution of the vector of actual symptoms knowing the current vector of faults, the proposed vector of faults, the probabilistic distribution of the vector of actual symptoms knowing the proposed vector of faults, and an a priori probability distribution of occurrences of the values of the fault vector, said fault matrix grouping together the consequences of each fault on the internal physical quantities ∘ replacement or not of the current vector of faults by the proposed vector of faults as a function of the probability of acceptance of the proposed vector of faults, • characterisation of a fault by recording the number of iterations having involved said fault in a current vector of faults.