Method for diagnosing failure of a supercharged internal combustion engine, equipped with a supercharger comprising: - a compressor including an inlet linked to the outside air, and an outlet linked to the intake of the engine, - a turbine including an inlet linked to an exhaust manifold of the engine, and an outlet, and - fins with variable orientation, actuated by an actuator to vary the section of passage of the exhaust gases in the turbine, the turbine and the compressor being linked in rotation by a common shaft, characterized in that it comprises: - a first step of calculating a first estimated value ( POW t,CPR) of the power of the turbine from a first set of parameters comprising at least: a) the pressure ( P uc) of the air at the inlet of the compressor, b) the supercharging pressure ( P dc), c) the mass flow rate ( W c) of the air passing through the compressor, and d) the temperature ( T uc) of the air at the inlet of the compressor, - a second step of calculating a second estimated value ( POW t,VGT) of the power of the turbine from a second set of parameters comprising at least: e) the pressure (P dt) of the gases at the outlet of the turbine, f) the mass flow rate (W t) of the gases passing through the turbine, g) the temperature ( T ut) of the gases at the inlet of the turbine, h) a position ( u VGT) of the actuator actuating the fins, and i) the speed of rotation ( N tc) of the turbocharger, - a third step of determining a power ratio (ε t) calculated as the ratio of the second estimated value ( POW t,VGT) of the power of the turbine, divided by the first estimated value ( POW t,CPR) of the power of the turbine, - a fourth step of comparing the power ratio (ε t) with a threshold, and - a fifth step of diagnosing failure of the engine when the power ratio (ε t) is above the threshold. - a compressor including an inlet linked to the outside air, and an outlet linked to the intake of the engine, - a turbine including an inlet linked to an exhaust manifold of the engine, and an outlet, and - fins with variable orientation, actuated by an actuator to vary the section of passage of the exhaust gases in the turbine, - a first step of calculating a first estimated value ( POW t,CPR) of the power of the turbine from a first set of parameters comprising at least: a) the pressure ( P uc) of the air at the inlet of the compressor, b) the supercharging pressure ( P dc), c) the mass flow rate ( W c) of the air passing through the compressor, and d) the temperature ( T uc) of the air at the inlet of the compressor, a) the pressure ( P uc) of the air at the inlet of the compressor, b) the supercharging pressure ( P dc), c) the mass flow rate ( W c) of the air passing through the compressor, and d) the temperature ( T uc) of the air at the inlet of the compressor, - a second step of calculating a second estimated value ( POW t,VGT) of the power of the turbine from a second set of parameters comprising at least: e) the pressure (P dt) of the gases at the outlet of the turbine, f) the mass flow rate (W t) of the gases passing through the turbine, g) the temperature ( T ut) of the gases at the inlet of the turbine, h) a position ( u VGT) of the actuator actuating the fins, and i) the speed of rotation ( N tc) of the turbocharger, e) the pressure (P dt) of the gases at the outlet of the turbine, f) the mass flow rate (W t) of the gases passing through the turbine, g) the temperature ( T ut) of the gases at the inlet of the turbine, h) a position ( u VGT) of the actuator actuating the fins, and i) the speed of rotation ( N tc) of the turbocharger, - a third step of determining a power ratio (ε t) calculated as the ratio of the second estimated value ( POW t,VGT) of the power of the turbine, divided by the first estimated value ( POW t,CPR) of the power of the turbine, - a fourth step of comparing the power ratio (ε t) with a threshold, and - a fifth step of diagnosing failure of the engine when the power ratio (ε t) is above the threshold.