Method for diagnosing the operation of an automatic or semi-automatic device for accessing a transport vehicle comprising at least one opening part adapted to be actuated by a kinematic chain including at least one motor powered electrically and having an associated angular position and/or rotational speed encoder and, preferably at least one switch, the access device being movable between an opening position and a closing position, characterised in that it includes steps, implemented by a processor, for at least one cycle of actuating the kinematic chain between a first position among the opening and closing positions and a second position, different from the first position, among the closing and opening positions, consisting in: - during said cycle, acquiring information relating to the kinematic chain comprising at least one piece of information representative of the electrical energy consumed by the motor, and/or position and/or speed information provided by said encoder and/or binary information indicating switch positions of the actuation kinematic chain, - dividing said cycle into a plurality of functional segments according to said acquired information, - calculating at least one descriptor value per functional segment, each functional segment having an associated time interval, and the descriptors being representative of the electrical energy consumed during said time interval and/or of a duration of the functional segment, - calculating one or more individual health indicators per functional segment, - establishing an operating diagnosis comprising a degradation detection according to at least some of said calculated descriptor values, and, in the event of degradation being detected, the method further includes: - a calculation of at least one signature vector including at least some of the individual health indicators, - estimating a measure of similarity between said signature vector and at least one reference signature vector representative of a type of degradation, and - an identification of a type of degradation according to the estimation of a measurement of similarity. characterised in that it includes steps, implemented by a processor, for at least one cycle of actuating the kinematic chain between a first position among the opening and closing positions and a second position, different from the first position, among the closing and opening positions, consisting in: - during said cycle, acquiring information relating to the kinematic chain comprising at least one piece of information representative of the electrical energy consumed by the motor, and/or position and/or speed information provided by said encoder and/or binary information indicating switch positions of the actuation kinematic chain, - dividing said cycle into a plurality of functional segments according to said acquired information, - calculating at least one descriptor value per functional segment, each functional segment having an associated time interval, and the descriptors being representative of the electrical energy consumed during said time interval and/or of a duration of the functional segment, - calculating one or more individual health indicators per functional segment, - establishing an operating diagnosis comprising a degradation detection according to at least some of said calculated descriptor values, - during said cycle, acquiring information relating to the kinematic chain comprising at least one piece of information representative of the electrical energy consumed by the motor, and/or position and/or speed information provided by said encoder and/or binary information indicating switch positions of the actuation kinematic chain, - dividing said cycle into a plurality of functional segments according to said acquired information, - calculating at least one descriptor value per functional segment, each functional segment having an associated time interval, and the descriptors being representative of the electrical energy consumed during said time interval and/or of a duration of the functional segment, - calculating one or more individual health indicators per functional segment, - establishing an operating diagnosis comprising a degradation detection according to at least some of said calculated descriptor values, and, in the event of degradation being detected, the method further includes: - a calculation of at least one signature vector including at least some of the individual health indicators, - estimating a measure of similarity between said signature vector and at least one reference signature vector representative of a type of degradation, and - an identification of a type of degradation according to the estimation of a measurement of similarity. - a calculation of at least one signature vector including at least some of the individual health indicators, - estimating a measure of similarity between said signature vector and at least one reference signature vector representative of a type of degradation, and - an identification of a type of degradation according to the estimation of a measurement of similarity.